CN109804479A

CN109804479A - Hot carrier solar battery and forming method thereof

Info

Publication number: CN109804479A
Application number: CN201780037453.3A
Authority: CN
Inventors: 岑子健; 李明杰; 苏博高塔姆·玛瑟卡; N·马修斯
Original assignee: Nanyang Technological University
Current assignee: Nanyang Technological University
Priority date: 2016-07-27
Filing date: 2017-07-20
Publication date: 2019-05-24
Anticipated expiration: 2037-07-20
Also published as: CN109804479B; WO2018021966A2; WO2018021966A3

Abstract

Various embodiments can provide hot carrier solar battery.The solar battery may include nanocrystal layer, and the nanocrystal layer includes or comprising one or more nanocrystals, each in one or more nanocrystals includes halide perovskite material.The hot carrier solar battery can also include the first electrode with the first side contacts of nanocrystal layer.The hot carrier solar battery can also include the second electrode with the second side contacts of nanocrystal layer, wherein described second side is opposite with first side.Nanocrystal layer can have the thickness less than 100nm.

Description

Hot carrier solar battery and forming method thereof

Related application

This application claims the priority for the Singapore patent application No.10201606182S that on July 27th, 2016 submits, Content is incorporated herein by reference in their entirety.

Technical field

Various aspects of the disclosure is related to hot carrier solar battery.Various aspects of the disclosure is related to hot carrier too The forming method of positive energy battery.

Background technique

A current generally existing feature of all solar batteries is that solar photon (from ultraviolet to infrared wavelength) has The energy bigger than semiconductor band gap can produce free carrier or exciton with the excess energy beyond band gap；These Carrier or exciton temperature are higher than material lattice temperature, referred to as " hot carrier " or " heat shock ".The carrier of this surplus Energy is dynamics free energy and superfluous kinetic energy is converted into heat rapidly (in subpicosecond by Electron-phonon scattering In time scale) loss.1961, it was other unique free energy that Shockley and Queisser (SQ), which are based on radiation recombination, Loss mechanism and complete hot carrier it is cooling it is assumed that calculating solar irradiance in solar battery is converted to electric free energy Maximum possible thermodynamic efficiency.It is 31-33% that theoretical maximum thermodynamic efficiency, which is calculated, in this, and best band gap is in about 1.1eV Between 1.4eV.

The calculation of thermodynamics of nineteen eighty-two shows first if utilizing hot photo-generated carrier before being cooled to lattice temperature Excess energy, then transfer efficiency can achieve 66%, to limit more than SQ and improve solar battery efficiency.A kind of method is Hot carrier is transferred to the carrier collection contact with appropriate work function before carrier is cooling.These batteries are referred to as Hot carrier solar battery.Therefore, research circle constantly looking for hot carrier cooling characteristics at a slow speed it is suitable too Positive energy battery absorbing material.

During the early-stage development of nanotechnology, it is initially considered that by phonon bottleneck effect semiconductor nanocrystal (NC) Quantum confinement can slow down hot carrier cooling procedure.However, quick relaxation road of the further studies have shown that due to substitution Line can exceed that phonon bottleneck, therefore realize that hot carrier cooling is still challenging at a slow speed in quantum confinement system.Cause This, it is highly desirable to develop the new material with hot carrier cooling performance at a slow speed.

Summary of the invention

Various embodiments can provide hot carrier solar battery.The solar battery may include nanocrystal layer, The nanocrystal layer includes or comprising one or more nanocrystal, each packet in one or more nanocrystals Include halide perovskite material.The hot carrier solar battery can also include with the first side contacts of nanocrystal layer One electrode.The hot carrier solar battery can also include the second electrode with the second side contacts of nanocrystal layer, wherein Described second side is opposite with first side.Nanocrystal layer can have the thickness less than 100nm.

Various embodiments can provide the forming method of hot carrier solar battery.This method may include providing or being formed Nanocrystal layer including one or more nanocrystals (as described herein), it is each in one or more nanocrystals Kind includes halide perovskite material.This method can also include forming first electrode, so that first electrode and nanocrystal layer The first side contacts.This method can also include forming second electrode, so that the second of second electrode and nanocrystal layer flanks Touching, wherein described second side is opposite with first side.Nanocrystal layer can have the thickness less than 100nm.

Detailed description of the invention

The present invention may be better understood in conjunction with non-limiting embodiment and attached drawing and with reference to detailed description, in which:

Fig. 1 shows the general legend of nanocrystal according to various embodiments.

Fig. 2 shows the general legends of hot carrier solar battery according to various embodiments.

Fig. 3 shows the schematic diagram of the forming method of nanocrystal according to various embodiments.

Fig. 4 shows the schematic diagram of the forming method of hot carrier solar battery according to various embodiments.

Fig. 5 shows in semiconductor nanocrystal (a) with interior Auger energy transmission, (b) phonon bottleneck effect and (c) interband Auger The cooling schematic diagram of the hot carrier of process.

Fig. 6 show according to various embodiments there is opposite (a) small size, (c) in size and (e) large-sized methyl amine bromine Change lead perovskite (MAPbBr₃) nanocrystal (NC) typical transmission electron microscope (TEM) image, be corresponding on the right of it Size histogram (b, d, f).Size distribution can be modeled with Gaussian Profile.

Fig. 7 shows methyl amine lead bromide (MAPbBr₃) body block film (a) top view and (b) side view scanning electron microscopy Mirror (SEM) image.

Fig. 8 shows (a) luminescence generated by light (PL) intensity (arbitrary unit or a.u.) to the curve graph of wavelength (nanometer or nm), indicates The methyl amine lead bromide perovskite (MAPbBr according to various embodiments being dispersed in toluene₃) nanocrystal (NC) and body block Luminescence generated by light (PL) spectrum of film counterpart；(b) absorbance (arbitrary unit or a.u.) is to the curve graph of wavelength (nanometer or nm), Indicate the methyl amine lead bromide perovskite (MAPbBr according to various embodiments being dispersed in toluene₃) nanocrystal (NC) and Ultraviolet-visible (UV-vis) absorption spectrum of body block film counterpart；(c) 1s exciton energy E_1s(electron volts or eV) is to nanocrystal The curve graph of mean radius a (nanometer or nm) indicates methyl amine lead bromide perovskite (MAPbBr according to various embodiments₃) The energy of 1s exciton and the relationship of radius, and (d) X-ray diffraction (XRD) intensity (arbitrary unit or a.u.) to 2 θ of angle (with Degree be unit) curve graph, indicate three kinds of various sizes of methyl amine lead bromide perovskites according to various embodiments (MAPbBr₃) nanocrystal (NC) XRD diagram.

Fig. 9 A shows middle size methyl amine lead bromide perovskite nanocrystal in the solution according to various embodiments (MAPbBr₃NC) pseudo-colours transient absorption (TA) figure (upper figure, time (picosecond or ps) and the energy (electronics of (radius~4-5nm) Volt or eV) relational graph) and normalization transient absorption (TA) spectrum (following figure, normalized transmittance change Delta T/T are (electric to energy Son volt or eV) curve graph), wherein under low pump power density (left figure), electronics-that initial every nanocrystal averagely generates Hole is to for < N₀(the average carder density n of every nanocrystal volume of >~0.1_0avg~2.6 × 10¹⁷cm^-3), in high pumping function (right figure) < N under rate density₀(the n of >~2.5_0avg~6.5 × 10¹⁸cm^-3)。

Fig. 9 B shows MAPbBr₃The pseudo-colours of body block film indicates that (upper figure and normalizes transient absorption at the time (picosecond or ps) (TA) spectrum (following figure, curve graph of the normalized transmittance change Delta T/T to energy (electron volts or eV)).It is close in low pump power Under degree (left figure), the carrier density initially generated is n₀~2.1 × 10¹⁷cm³, (right figure) n under high pump power densities₀~ 1.5×10¹⁹cm³。

Figure 10 shows the time (picosecond or ps) to the curve graph of energy (electron volts or eV), indicates in the solution according to various realities Apply (a) small size and (b) large-sized methyl amine lead bromide perovskite nanocrystal (MAPbBr of example₃NC) pseudo-colours transient state is inhaled Receive (TA) spectrum (by picosecond or ps as unit of time to the energy as unit of electron volts or eV).After the excitation of 3.1eV light, (left figure) electron-hole pair that initially every nanocrystal averagely generates is < N under low pump power density₀>~0.1, in high pumping (right figure) < N under power density₀>~2.5.

Figure 11 shows (a) normalized transmittance change Delta T/T to the curve graph of energy (electron volts or eV), indicates in toluene The methyl amine lead bromide perovskite nanocrystal (MAPbBr of middle size according to various embodiments₃NC) in different short delays Between under normalization TA spectrum, electron-hole pair < N that every nanocrystal averagely generates₀>~0.1 (after the excitation of 3.1eV light)；With And (b) (a) does not normalize transient absorption (TA) spectrum.

Figure 12 shows carrier temperature (Kelvin or K) to the curve graph of time (picosecond or ps), indicates in various pumping function Under rate density, the hot carrier temperature T of middle sized nanocrystals (NC) and body block film according to various embodiments_cTime drill Become: initial light activated hot carrier density n₀Electron-hole pair < N that (body block film) and every NC are averagely generated₀>, wherein<N₀> =J σ, wherein J is pump power density, and σ is absorption cross-section.

Figure 13 shows curve graph of (a) luminescence generated by light (PL) intensity (arbitrary unit or a.u.) to time (nanosecond or ns), table Show middle size methyl amine lead bromide perovskite nanocrystal (MAPbBr according to various embodiments₃NC) under the excitation of 3.1eV light The pump power density of time resolution luminescence generated by light (PL) relies on；(b) transient photoluminescence (PL) intensity (arbitrary unit or A.u.) to the curve graph of pump intensity (micro- joule/square centimeter or μ J cm^-2), indicate three kinds of differences according to various embodiments The MAPbBr of size₃NC normalizes PL intensity to the relational graph of pump power density at time of measuring Δ t=4ns；And (c) Probability (percentage or %) is occupied to the curve graph of the quantity of the electron-hole (e-h) pair of each NC according to various embodiments.

In table shown in Figure 14, methyl amine lead bromide perovskite nanocrystal according to various embodiments is compared (MAPbBr₃NC), the property of methyl amine lead bromide perovskite body block film and other materials reported in the literature.

Figure 15 shows three kinds of various sizes of methyl amine lead bromide perovskite nanocrystals according to various embodiments (MAPbBr₃NC) and carrier temperature (Kelvin or K) of the body block film after the excitation of 3.1eV light is to time delay (picosecond or ps) Curve graph, wherein (a) (is equivalent in NC < N under low pump power density₀>~0.1, n in body block film₀~2.1 × 10¹⁷cm³), (b) (< N is equivalent in NC under high pump power densities₀>~2.5, n in body block film₀~1.5 × 10¹⁹cm³)。

Figure 16 shows normalized transmittance change Delta T/T to the curve graph of time (picosecond or ps), indicates first in the solution Base amine lead bromide (a) body block film, (b) small size nanocrystal (NC) according to various embodiments, (c) are according to various embodiments Middle sized nanocrystals (NC) and (d) macro nanometer crystal (NC) according to various embodiments are respectively in high pump power densities Under low pump power density, in the photic bleaching kinetics of normalization of band edge detection；And (e) in the solution according to various The transient absorption (TA) of the middle sized nanocrystals (NC) of embodiment and Spincoating of nanocrystal (NC) film according to various embodiments Dynamics compares；And (f) small size methyl amine lead bromide nanocrystal (NC) according to various embodiments in the solution exists The pump power density of the bleaching kinetics of band edge detection relies on.

Figure 17 shows (a) rate of energy loss (every picosecond of eV ps of electron volts^-1) to the curve of carrier temperature (Kelvin or K) Figure, indicates methyl amine lead bromide perovskite nanocrystal (MAPbBr according to various embodiments₃NC) (wherein < N₀>~0.1) with Methyl amine lead bromide perovskite (MAPbBr₃) body block film (wherein n₀~2.1 × 10¹⁷cm^-3) carrier temperature T_cTo hot current-carrying The relational graph of the rate of energy loss of son；(b) normalized transmittance change Delta T/T indicates the curve graph of time (picosecond or ps) Colloid methyl amine lead bromide perovskite nanocrystal (MAPbBr according to various embodiments₃NC) and body block film is close in low carrier Under degree, the normalization bleaching kinetics of band edge detection；And (c) rise time (femtosecond or fs)/limitation energy (electron volts or EV curve graph) indicates methyl amine lead bromide perovskite nanocrystal (MAPbBr₃NC) (black solid square), body block film are (shallow Color closed square) band edge bleaching is upper in (partial size is indicated by film thickness) and cadmium selenide nano crystal (CdSe NC) (filled circles) The size for rising the time relies on and MAPbBr₃The ruler of quantum confinement energy in NCs (hollow square) and CdSe NC (open circles) Very little dependence.

Figure 18 shows raman scattering intensity (arbitrary unit or a.u.) to wave number (per cm or cm^-1) curve graph, indicate according to each The methyl amine lead bromide perovskite nanocrystal (MAPbBr of kind embodiment preparation₃NC) the Room temperature Raman of drop coating on the glass substrate Spectrum.

Figure 19 shows (a) normalized transmittance change Delta T/T to the curve graph of time (picosecond or ps), indicates to have different straight The colloid CdSe NC (being shown in legend) of the diameter normalization bleaching kinetics that band edge detects under low pump power density；With And (b) time (picosecond or ps) to the curve graph (electron volts or eV) of energy, indicates under low pump power density initially generation < N₀ >~0.1 (left side), under high pump power densities<N₀>~2.5 (right side).Light excitation energy is 3.1eV.

Figure 20 shows (a) rate of energy loss (every picosecond of electron volts or eV ps^-1) to the song of carrier temperature (Kelvin or K) Line chart indicates methyl amine lead bromide perovskite nanocrystal MAPbBr according to various embodiments₃NC(<N₀>~2.5) and MAPbBr₃Body block film (n₀~1.5 × 10¹⁹cm^-3) rate of energy loss and carrier temperature T_cRelationship；(b) service life (picosecond or Ps) to nanocrystal volume (cubic nanometer or nm³) curve graph, illustrate perovskite nanocrystal according to various embodiments (NC) relationship in volume and auger recombination service life and hot carrier cooling time, and (c) normalize hot carrier concentration n_hotClock synchronization Between (picosecond or ps) curve graph, indicate the normalized hot carrier under different pump power densities according to various embodiments Decay.

Figure 21 is rate of energy loss (every picosecond of electron volts or eV ps^-1) to the curve graph of carrier temperature (Kelvin or K), table Show methyl amine lead bromide (MAPbBr₃) hot carrier energy loss of the body block film under low carrier density and high carrier density Rate and carrier temperature T_cRelationship.

Figure 22 shows photoelectron intensity (counting per second or cts/s) to the curve graph of energy (electron-volt or eV), indicates The basis of (a) 1,2- dithioglycol (EDT) processing on tin indium oxide (ITO) substrate handled with (b) through the EDT of after annealing is each Methyl amine lead bromide (the MAPbBr of kind embodiment₃) nanocrystal (NC) film, and (c) 7- diphenyl -1,10- phenanthroline (Bphen) ultraviolet photoelectron spectroscopy (UPS) of film.

Figure 23 A is flat rubber belting energy diagram (vertical axis electron-volt or eV), to illustrate from perovskite nanometer according to various embodiments The thermoelectron of crystal to 7- diphenyl -1,10- phenanthroline (Bphen) extracts and the cooling approach of the thermoelectron of competition.

Figure 23 B shows the atomic force of nanocrystal (NC) film of the processing of 1,2- dithioglycol (EDT) according to various embodiments Microscope (AFM) image.

Figure 23 C is nanocrystal (NC)/7- diphenyl -1,10- of 1,2- dithioglycol (EDT) processing according to various embodiments Scanning electron microscope (SEM) image of phenanthroline (Bphen) duplicature.

Figure 23 D is curve graph of the normalized transmittance change Delta T/T to energy (electron-volt or eV), is indicated according to various implementations Example has the 1,2- ethylene dithiol of (continuous lines)/about 35nm thickness without (dotted line) 7- diphenyl -1,10- phenanthroline (Bphen) Nanocrystal (NC) film of alcohol (EDT) processing (< N after 3.1eV photoexcitation₀> normalization transient absorption (TA) about 0.1) Spectrum.

Figure 23 E is nanocrystal (NC) film and 1,2- ethylene dithiol of 1,2- dithioglycol (EDT) processing according to various embodiments Nanocrystal (NC) film/7- diphenyl -1,10- phenanthroline (Bphen) duplicature of alcohol (EDT) processing is in different pump powers Curve graph of the hot carrier temperature (Kelvin or K) to delay time (picosecond or ps) under density.

Figure 23 F is extraction efficiency η_hot(percentage or %) indicates the curve graph of thermoelectron excess energy (electron-volt or eV) Nanocrystal (NC)/7- diphenyl -1,10- of 1,2- dithioglycol (EDT) processing of about 35nm thickness is luxuriant and rich with fragrance according to various embodiments The pump energy for coughing up thermoelectron extraction efficiency in quinoline (Bphen) duplicature relies on.

Figure 23 G is extraction efficiency η_hot(percentage or %) indicates according to various embodiments the curve graph of thickness (nanometer or nm) 1,2- dithioglycol (EDT) processing nanocrystal (NC)/7- diphenyl -1,10- phenanthroline (Bphen) duplicature and body block The calcium titanium of film/7- diphenyl -1,10- phenanthroline (Bphen) duplicature thermoelectron extraction efficiency after the excitation of 3.1eV pump energy Mine film thickness relies on.

Figure 24 (a) shows transmissivity (arbitrary unit or a.u.) to wave number (per cm or cm^-1) curve graph, indicate basis Methyl amine lead bromide nanocrystal (MAPbBr prepared by various embodiments₃NCs), what 1,2- dithioglycol (EDT) was handled receives Decaying total reflection-Fourier of meter Jing Ti (EDT-NC) and the 1,2- dithioglycol nanocrystal (Ann-EDT-NC) of 70 DEG C of annealing Transform infrared (ATR-FTIR) spectrum；And light emitting intensity (arbitrary unit or a.u.) is to combination energy (electron-volt or eV) Curve graph indicates receiving for (b) unannealed 1,2- dithioglycol (EDT) processing with (c) 70 DEG C of after annealings according to various embodiments Sulphur (S) the 2p x-ray photoelectron spectroscopy (XPS) of meter Jing Ti (EDT-NC) film.

Figure 25 shows the untreated middle size methyl amine lead bromide nanocrystal of (a) according to various embodiments (MAPbBr₃NC) atomic force microscope (AFM) image of film, and (b) according to various embodiments 1,2- dithioglycol processing The methyl amine lead bromide nanocrystal (MAPbBr of EDT processing₃NC) representative transmission electron microscope (TEM) image.

Figure 26 shows the middle size methyl amine lead bromide nanocrystal (MAPbBr of (a) according to various embodiments₃NC) film, (b) Nanocrystal (NC of EDT processing) film of 1,2- dithioglycol processing according to various embodiments, and (c) according to various embodiments The processing of 1,2- dithioglycol the nanocrystal film/7- diphenyl -1,10- phenanthroline NC film/Bphen of processing (EDT) it is double-deck Film (left figure, < N under low pump power density₀>~0.1) and high pump power densities under (right figure,<N₀>~2.5) pseudo-colours Transient absorption (TA) spectrum.

Figure 27 is shown energy diagram (y-axis: the energy as unit of electron-volt or eV), is indicated by ultraviolet photoelectron spectroscopy (UPS) and ultraviolet-visible (UV-VIS) spectral measurement determine non-annealing according to various embodiments, annealing 1,2- ethylene dithiol The alignment of the flat rubber belting energy level of alcohol-nanocrystal (EDT-NC) film and 7- diphenyl -1,10- phenanthroline (Bphen), mentions for thermoelectron The case where taking is illustrated.

Figure 28 (a) shows absorbance (arbitrary unit or a.u) to the curve graph of wavelength (nanometer or nm), indicates on glass The linear absorption spectrum of Bphen film；(b) normalize the variation of negative transmissivity --- Δ T/T to the curve graph of wavelength (nanometer or nm), Indicate that 7- diphenyl -1,10- phenanthroline (Bphen) (300nm pump intensity is 20 μ J cm^-2；400nm pump intensity is 40 μ J cm^-2), (400nm pump intensity is 15 μ J cm for perovskite nanocrystal (NC) according to various embodiments^-2) and according to various realities Applying 1,2- dithioglycol nanocrystal/7- diphenyl -1,10- phenanthroline (EDT-NC/Bphen) of example, (400nm pump intensity is 15μJ cm^-2) 2ps after excitation negative transient absorption spectra；(c) time, (picosecond or ps) was to the curve of wavelength (nanometer or nm) Figure indicates nanocrystal/7- diphenyl -1,10- phenanthroline (EDT- of 1,2- dithioglycol processing according to various embodiments NC/Bphen) duplicature pump intensity is 15 μ J cm^-2Light activated pseudo-colours transient absorption (TA) spectrum of 400nm；(d) Normalizing the variation of negative transmissivity --- Δ T/T is to the curve graph of time (picosecond or ps), with the light activated Bphen of 300nm and root Nanocrystal/7- diphenyl -1,10- the phenanthroline (EDT-NC/Bphen) handled according to the 1,2- dithioglycol of various embodiments is double Tunic 400nm optical pumping, the negative transient absorption spectra of the normalization detected at 1300nm.

Figure 29 is normalized transmittance change Delta T/T to the curve graph of time (picosecond or ps), is indicated according to various embodiments The nanometer of nanocrystal (EDT-NC) film of 1,2- dithioglycol processing and 1,2- dithioglycol processing according to various embodiments Crystal/7- diphenyl -1,10- phenanthroline (EDT-NC/Bphen) duplicature (< N under (a) low pump power density₀>~0.1) (b) (< N under high pump power densities₀>~2.5) the light activated normalization band edge bleaching kinetics of 3.1eV.

Figure 30 A is curve graph of the normalized transmittance change Delta T/T to energy (electron-volt or eV), is indicated according to various implementations The 1,2- second two that there are (continuous lines) and do not have (dotted line) 7- diphenyl -1,10- phenanthroline (Bphen) extract layer of example annealing Size methyl amine lead bromide nanocrystal (MAPbBr in thiol treatment (EDT processing)₃NC) film under low pump power density < N₀> ~0.1 normalization transient absorption spectra.

Figure 30 B is carrier temperature (Kelvin or K) to the curve graph of time (picosecond or ps), is indicated according to various embodiments Relationship of the extraction hot carrier temperature of two samples to delay time.

Figure 30 C is curve graph of the normalized transmittance change Delta T/T to energy (electron-volt or eV), indicates there is (continuous lines) With the methyl amine lead bromide (MAPbBr for not having (dotted line) 7- diphenyl -1,10- phenanthroline (Bphen) extract layer₃) body block film (~240nm is thick) 2 × 10 under low pump power density¹⁷cm^-3Normalization transient absorption (TA) spectrum.

Figure 30 D show the carrier temperatures (Kelvin or K) of two samples according to various embodiments to time delay (picosecond Or ps) curve graph.

Figure 31 shows the nanocrystal (EDT-NC of the processing of 1,2- dithioglycol with different thickness according to various embodiments Film) cross sectional Scanning Electron microscope (SEM) image.

Specific embodiment

Attached drawing is shown by way of diagram can practice detail and embodiment of the invention.Below with reference to Attached drawing is described in detail these embodiments, it is sufficient to those skilled in the art be enable to implement the present invention.It can be used His embodiment, and structure, logic can be carried out without departing from the scope of the invention and electrical changed.Various implementations Example be not necessarily it is mutually exclusive because some embodiments can be combined with one or more other embodiments to form new reality Apply example.

The embodiment described under a kind of method or nanocrystal/solar battery/device background is for other methods Or nanocrystal/solar battery/device is similarly effective.Similarly, the embodiment described under the background of method is to nanometer Crystal/solar battery/device is similarly effective, and vice versa.

The feature described under the background of embodiment can correspondingly apply to the same or similar in other embodiments Feature.Even if not being expressly recited in these other embodiments, the feature described under the background of embodiment can also be correspondingly Suitable for other embodiments.In addition, as embodiment background under feature described in addition and/or combination and/or replace In generation, can correspondingly apply to the same or similar feature in other embodiments.

One word of "upper" used about the deposition materials in side or the formation of surface "upper" can be used herein to mean that Deposition materials can " directly " be formed, such as directly be contacted, on implicit side or surface.About on side or surface One word of "upper" that uses of deposition materials that "upper" is formed can also be used herein to mean that deposition materials can shape " indirectly " At on implicit side or surface, added wherein arrangement is one or more between implicit side or surface and deposition materials Layer.In other words, the first layer in second layer "upper" can refer to first layer directly on the second layer or first layer and the second layer It is separated by one or more middle layers.

In the context of various embodiments, about the article " one " that feature or element use, "one" and "the" include Reference to one or more features or element.

It include exact value and reasonable side applied to the term " about " of numerical value or " approximation " in the context of various embodiments Difference.

As it is used herein, term "and/or" includes any and all combinations of one or more related listed items.

Since 2013, organic and inorganic lead halide perovskite semiconductor (such as MAPbX₃, MA=CH₃NH₃, X=I, Br Or Cl) have become for one of high-performance and the most promising material family of low-cost solar battery.The calcium of solution processing Titanium ore polycrystal film has been used as the light absorbing layer in solar cell device.At present according to records, with MAPbX₃As absorption Efficiency in the laboratory of the solar battery based on perovskite of body can be~20%.Recently, to MAPbI₃It is slow in film The cooling observation with thermal phonon bottleneck effect of speed heat carrier shows that lead halide perovskite may be building hot carrier solar energy The material of the great prospect of battery.

Fig. 1 shows the general legend of nanocrystal 100 according to various embodiments.Nanocrystal 100 may include halogenation Object perovskite material.

The diameter of nanocrystal can be selected from the range of 1nm to 100nm, such as 4nm to 14nm or 4nm to 13nm.

The radius of nanocrystal can be selected from any one value from 0.5nm to 50nm (such as from 2nm to 7nm).

In current context, " from X to Y " or " range of X to Y " indicate the range in addition to all values between X and Y it It outside, further include X and Y value.

Various embodiments can slow down heat by phonon bottleneck effect or interband Auger process (also referred to as Auger heating) Carrier cooling procedure.Various embodiments can be used in solar battery, can pass through the photon collection more than band gap Excess energy overcomes SQ to limit, to improve efficiency.

Previously to inorganic semiconductor nanocrystal (NC) as slow down the candidate material of hot carrier cooling procedure into Research is gone.However, the hot carrier in these inorganic semiconductor nanocrystals harvests the height by the phonon bottleneck for overwhelming it Spend the influence of the relaxation pathway (for example, with interior Auger process, defect) of competition.For example, according to Kilina etc., due to Auger mistake Journey and fault of construction, (" quantum Zeno effect makes half to influence still unpredictable of the phonon bottleneck to cadmium selenide (CdSe) quantum dot Phonon bottleneck in conductor quantum dot rationalizes ", physical comment bulletin 110,180404, the 1-6 pages, 2013).

Surprisingly, it was found that colloid halide perovskite NC may surmount these limitations.It is corresponding with its body block film Object is compared, and halide perovskite NC can show~2 orders of magnitude long hot carrier cooling time and~4 times high of heat carries Flow sub- temperature., it is surprising that the hot carrier mediated by phonon bottleneck is cooling in lesser NC under low pump excitation It may be slower (compared with traditional NC, cooling time shortens as size reduces).Under high pump power densities, Auger adds Heat may dominate hot carrier cooling, in biggish NC relatively slow (not observing in conventional NC so far).

The present inventor is demonstrated by the energy selectivity electron extraction layer from surface treated perovskite NC film Effective room temperature thermoelectron extracts (up to~83%) in 1 picosecond (ps).These opinions can be used for very thin absorber And/or the new method of optically focused hot carrier solar battery.

Halide perovskite material can be by general formula AMX₃It indicates, wherein A can be the organic or inorganic of one positive electricity of band just Ion (such as organic group or organic cation or positive metal ions or element) or organic and/or inorganic cation mixture. M can be divalent metal cation or element, and X can be halogen anion or element.Example may include CH₃NH₃PbI₃ (MAPbI₃)、CH₃NH₃PbBr₃(MAPbBr₃)、CH₃NH₃PbBr₂I(MAPbBr₂I)、CsSnI₃、CsPbI₃、NH₂CH=NH₂PbI₃ (FAPbI₃)、FA_1-yCs_yPbI₃Or Cs_x(MA_1-yFA_y)_1-xPb(I_1-zBr_z)₃(each of wherein x, y or z be all 0 to 1 it Between number).MA can be with nail amine (CH₃NH₃), and FA can be with nail amidine (NH₂CH=NH₂)。

In various embodiments, bivalent positive ion can be Pb²⁺Or Sn²⁺.In other words, M can be lead (Pb) or tin (Sn)。

In various embodiments, halide perovskite material may include one or more selected from I^-、Cl^-And Br^-Halide Anion.In other words, X₃It can be I₃、Cl₃、Br₃Or combinations thereof (such as Cl₂Br)。

In various embodiments, halide perovskite material may include organic ammonium cation.Organic ammonium cation A can be selected From ammonium cation, hydroxylammonium cation, first ammonium cation (MA⁺), hydrazine cation, azetidine cation, carbonamidine cation (FA⁺), imidazoles cation, dimethylammonium cation, second ammonium cation, phenethyl ammonium cation, guanidine cation and combinations thereof.Organic ammonium Cation can be with general formula C_nH_2n+1NH₃₊Cation, wherein 2 < n < 20.In other words, A can be C_nH_2n+1NH₃.? In various embodiments, halide perovskite material may include positive metal ions, such as cesium ion (Cs⁺)。

Nanocrystal 100 can be shown the hot carrier cooling service life of any at least 0.5ps, for example, from 0.5ps to 40ps.The hot carrier cooling service life can be defined as from pulse excitation until hot carrier is cooled to the time interval of 600K.

Fig. 2 shows the general legends of hot carrier solar battery 200 according to various embodiments.Solar battery 200 may include nanocrystal layer 202 comprising or include one or more nanocrystals (as described herein), described one kind Or each in a variety of nanocrystals includes halide perovskite material.The hot carrier solar battery 200 can also wrap Include the first electrode 204 with the first side contacts of nanocrystal layer 202.The hot carrier solar battery 200 can also include With the second electrode 206 of the second side contacts of nanocrystal, wherein described second side is opposite with first side.Nanocrystal layer 202 can have the thickness less than 100nm.

In other words, solar battery 200 may include nanocrystal layer 202 comprising one or more nanocrystals. Layer 202 can be clipped among electrode 204,206.

Nanocrystal layer 202 is alternatively referred to as absorbed layer or hot carrier absorber.In various embodiments, the thickness of layer 202 Degree can be less than hot carrier diffusion length, so that hot carrier can be extracted by electrode 204,206 before cooling.

Hot carrier solar battery 200 can receive incident light (from the sun) and can be configured as and is based on coming from The solar energy of incident light produces electricl energy.

In various embodiments, hot carrier solar battery 200 may further include solar energy (from the sun) It is directed to the Optical devices of nanocrystal layer 202.In various embodiments, hot carrier solar battery 200 can be optically focused Hot carrier solar battery.The Optical devices may include one or more optical elements with by solar energy to guide to nanocrystal Layer 202.The one or more optical element can be or may include optical lens and/or mirror.In higher pump power Under density, with the increase of photoexcited charge carrier density, hot carrier cooling may become slower.1 in nanocrystal Pump power density more than a electron-hole pair (corresponds to about 10¹⁸cm^-3Effective volume carrier density), hot carrier The cooling service life can exceed that 30ps (compared with the 1.5ps in body block film), this may be due to the Auger in quantum confinement system Fuel factor.These features are advantageously used for and some point for focusing the light into photovoltaic cell is upper with higher power density behaviour The concentrating solar battery of work.As will be shown later, compared with other materials, the hot carrier lifetime of perovskite NC is in high pump power It may be longer under density.These features are advantageously possible for the application of optically focused hot carrier solar battery, are carried by using heat Flowing sub- absorber can operate at higher illumination (about or more than 1000suns).

In various embodiments, hot carrier solar battery 200 can be unijunction solar cell.It is real in various substitutions It applies in example, hot carrier solar battery 200 can be multijunction solar cell.

In various embodiments, first electrode 204 can be or may include thermoelectron extract layer.

In various embodiments, first electrode 204 can be or may include n-layer.N-layer or thermoelectron extract layer can Including any one in following material: titanium oxide, zinc oxide, phenyl-C61- methyl butyrate (PCBM), 4,7- hexichol Base -1,10- phenanthroline (Bphen), poly- (9- vinyl carbazole) (PVK), 2- (4- xenyl) -5- phenyl -1,3,4- oxadiazoles (PBD), 2,2', 2 "-(1,3,5- benzene pawl base)-three (1- phenyl -1-H- benzimidazole) (TPBI), poly- (9,9- dioctyl fluorene) (F8) and bathocuproine (BCP).

In various embodiments, first electrode 204 can be energy selectivity contact point, allow have be equal to or higher than The electronics of the excess energy of predetermined value passes through, and can also will have the electron reflection for the excess energy for being lower than predetermined value to return to Nanocrystal layer 202.Under current background, excess energy can refer to the electronics of the conduction band minimum more than nanocrystal layer 202 Energy.The predetermined value of excess energy, which can be, to be selected from from any value in the range of about 0.1eV to 2eV.

In various embodiments, second electrode 206 can be or may include hot hole extract layer.

In various embodiments, second electrode 206 can be or may include p-type layer.

In various embodiments, second electrode 206 can be energy selectivity contact point, allow have be equal to or higher than The hole of the excess energy of predetermined value passes through, and can also will have the hole reflections for the excess energy for being lower than predetermined value to return to Nanocrystal layer 202.Under current background, excess energy can refer to the hole of the maximum price band more than nanocrystal layer 202 Energy.The predetermined value of excess energy, which can be, to be selected from from any value in the range of about 0.1eV to 2eV.In various embodiments, Second electrode 206 may include molecular semiconductor materials.P-type layer or hot hole extract layer may include any in following material It is a kind of: two fluorenes (spiro-OMeTAD) of 2,2', 7,7'- tetra- [N, N- bis- (4- methoxyphenyl) amino] -9,9'- spiral shell, it is poly- (3- oneself Base thiophene -2,5- pitch base) (P3HT), poly- (3,4- Ethylenedioxy Thiophene) poly styrene sulfonate (PEDOT:PSS) and it is poly- (9, 9- dioctyl-fluorenes-co-N- (4- butyl phenyl) diphenylamines (TFB).

In various embodiments, one or more nanocrystals show the hot carrier cooling longevity of at least 0.5ps Life, such as 30ps or more.The radius of each in one or more nanocrystals is selected from the range from 0.5nm to 50nm Interior arbitrary value, such as the arbitrary value from 2nm to 7nm in range.

In various embodiments, halide perovskite material can be organic and inorganic halide perovskite material, such as MAPbI₃、MAPbBr₃、MAPbBr₂I、FAPbI₃、FA_1-yCs_yPbI₃Or Cs_x(MA_1-yFA_y)_1-xPb(I_1-zBr_z)₃(wherein x, y or z Each of can be any value selected in from 0 to 1 range).Non-limiting specific example may include CH₃NH₃PbI₃、 CH₃NH₃PbBr₃、CH₃NH₃PbBr₂I or NH₂CH=NH₂PbI₃.In various other embodiments, halide perovskite material can be with It is inorganic halides perovskite material, such as CsSnI₃Or CsPbI₃。

Hot carrier may be needed quickly to extract with limit energy losses, wherein competition be present in extraction rate and Between cooling rate, rather than recombination rate.In various embodiments, described one can be handled with 1,2- dithioglycol (EDT) Kind or a variety of nanocrystals.

The MAPbBr handled from 1,2- dithioglycol (EDT) is demonstrated herein₃NC (EDT-NC) arrives diphenyl -1 4,7-, Effective hot carrier of 10- phenanthroline (Bphen) is extracted.Bphen be can choose as thermoelectron and extract material, because of the molecule Semiconductor has high electron mobility and the higher lowest unoccupied molecular orbital of conduction band minimum (CBM) than the NC of EDT processing (LUMO).EDT processing can be used for replacing the oleic acid for the length and high-insulation being present on the prepared surface NC to match with mercaptides Body, with more effectively with Bphen in NC film electron coupling.

Fig. 3 shows the schematic diagram 300 of the forming method of nanocrystal according to various embodiments.This method can wrap It includes: in 302, forming the nanocrystal including halide perovskite material using solwution method.

The diameter of nanocrystal can be selected from the range of 1nm to 100nm, such as 4nm to 14nm.

Solwution method may include that a variety of presomas and solvent are mixed to form precursor solution.A variety of presomas can wrap Include organic halogenation ammonium.Solwution method, which may further include, adds one or more ligands and/or one or more surfactants It is added in precursor solution.For example, methyl bromide ammonium (MABr, wherein MA represents methylamine) can be with lead bromide (PbBr₂) two Initial precursor solution is mixed to form in the solvent of methylformamide (DMF).Oleyl amine (OAm) and oleic acid (OAc) can be added It is added in DMF solvent to form final precursor solution, is used to form methyl amine lead bromide perovskite nanocrystal.

Solwution method, which may further include, heats other solvent.Other solvent can be heated to predetermined temperature, example Such as 60 DEG C.Solwution method, which can also comprise, is mixed to form nanometer for precursor solution and heated other solvent under stiring Crystal.Other solvent can be toluene.

Fig. 4 shows the schematic diagram 400 of the forming method of hot carrier solar battery according to various embodiments.The party Method may include: in 402, to provide or formed the nanocrystal layer comprising one or more nanocrystals (as described herein), Wherein each in one or more nanocrystals includes halide perovskite material.This method can also include: In 404, first electrode is formed, so that the first side contacts of first electrode and nanocrystal layer.This method can also include: In 406, form second electrode so that the second side contacts of second electrode and nanocrystal layer, wherein described second side with it is described First side is opposite.Nanocrystal layer can have the thickness less than 100nm.

In other words, the forming method of solar battery as described herein can be provided.Solar battery may include electricity Pole and nanocrystal layer comprising one or more nanocrystals as described herein.

To avoid doubt, method and step shown in Fig. 4 not necessarily successively carries out in order.For example, in various embodiments In, first electrode can be formed before forming nanocrystal layer.

In various embodiments, this method may further include to be formed the optics of solar energy to guide to nanocrystal layer Device.Optical devices may include one or more optical elements by solar energy to guide to nanocrystal layer.It is one or more A optical element can be or may include optical lens and/or mirror.

In various embodiments, first electrode 204 can be or may include n-layer.N-layer or thermoelectron extract layer can To include any one in following material: titanium oxide, zinc oxide, phenyl-C61- methyl butyrate (PCBM), 4,7- hexichol Base -1,10- phenanthroline (Bphen), poly- (9- vinyl carbazole) (PVK), 2- (4- xenyl) -5- phenyl -1,3,4- oxadiazoles (PBD), 2,2', 2 "-(1,3,5- benzene pawl base)-three (1- phenyl -1-H- benzimidazole) (TPBI), poly- (9,9- dioctyl fluorene) (F8) and bathocuproine (BCP).

In various embodiments, one or more nanocrystals show the hot carrier cooling longevity of at least 0.5ps Life, such as 30ps or more.The radius of each in one or more nanocrystals is selected from the range from 0.5nm to 50nm Any one interior value, such as any one value from 2nm to 7nm in range.

Various embodiments can provide the colloid MAPbBr of solution processing₃(methyl amine lead bromide) perovskite nanocrystal It (NC), is a kind of very promising absorbing material for hot carrier solar battery.Hot carrier is cooling may ratio Perovskite body block film is significantly slower.Under comparable photo-excitation conditions, MAPbBr₃Hot carrier in NC can increase cooling time It is added to 30ps (or higher), this about 2 order of magnitude slowly than its body block film counterpart.In addition, under comparable photo-excitation conditions, MAPbBr₃The hot carrier temperature of NC is 4 times bigger than its body block film counterpart.

The cooling dynamics of control hot carrier may be challenging, but for improving many photonic semiconductors and electricity The performance of sub- device is vital.In NC, hot carrier cooling time/rate may depend on volume and carrier is close Degree.Therefore, these discoveries be can use, it is cooling to control hot carrier by adjusting NC size and carrier injection density.

It is cooling the hot carrier in NC according to various embodiments can be adjusted by changing the size of NC.Due to limitation Caused phonon bottleneck effect, the hot carrier cooling rate in the NC of smaller size may be lower.Except MAPbBr₃Perovskite NC Outside, there are also perovskite NC, such as MAPbI that other organic principles and/or metallic element substitute₃、MAPbBr_xI_1-x(x is Br/ (Br+ I ratio) is determined by the content of Br in presoma and I in the synthesis process), CsSnI₃、CsPbI₃、FAPbI₃.NC can permit Perhaps a variety of hot carrier absorbers with different band gap are selected.In addition, after chemical surface treatment, the heat from NC film Electronics can be effectively injected (up to~83%) electron extraction layer in~1ps.These opinions can be hot carrier and gather Light perovskite NC photovoltaic device provides new method.

Various embodiments can be related to the preparation, hot at a slow speed of the organic and inorganic perovskite nanocrystal of cryogenic fluid processing The cooling observation of carrier and/or these nanocrystals are used for hot carrier solar battery and optically focused hot carrier solar energy The potential application of battery.With traditional hot carrier solar cell system on the contrary, optically focused hot carrier solar battery can be with Using condenser lens or curved mirror by solar light focusing 300 to 1000 times in small cell area.Therefore, light focusing unit can be with It is operated in the case where the light more much higher than conventional hot carrier solar battery generates current density.Higher injection density can cause Higher hot carrier temperature and longer hot carrier lifetime, this can be further improved the effect of hot carrier solar battery Rate.

Cryogenic fluid processing method in an atmosphere can be used to prepare nanocrystal.In contrast, traditional silicon substrate Solar battery is usually produced using high vacuum growing technology at high temperature, needs a large amount of infrastructure investment.

Calculation of thermodynamics show if before being cooled to lattice temperature utilize hot photo-generated carrier excess energy, Unijunction solar cell transfer efficiency can reach about 66% under 1-sun irradiation.Effectively extract hot carrier energy key be It is cooling to postpone hot carrier.It has been recognized that the impossibility of energy and the conservation of momentum and multiphonon process will lead to sound Sub- bottleneck, so that the hot carrier slowed down in semiconductor nano grade system is cooling.However, further investigations have shown that, with receiving The size reduction of meter level inorganic semiconductor, cooling rate become faster.

In many photons and electronic equipment, hot carrier cooling may be crucial.For with existing silicon-based technologies Integrated, solution-processible material has bigger multifunctionality than traditional material.By simple spin coating, dip-coating or drop coating, it It can be applied to wider device design and substrate.

Compared with the traditional silicon thin film for using expensive gas phase process production, the organic and inorganic perovskite of solution processing is received Meter Jing Ti can provide simple and cheap material substitutions for potential photovoltaic application.Low-temperature treatment can also make these materials It can be integrated into flexible base board.It is extracted with the effective hot carrier of permission for the absorber being used as in solar battery current Perovskite thin film is compared, and perovskite NC can have slower hot carrier cooling.These features are advantageously possible for realizing hot current-carrying Sub- solar battery.In addition, as observed in perovskite NC first hot current-carrying can also be adjusted by modification NC size Sub- cooling time/rate.

Various embodiments can be widely used for photovoltaic application field as absorbing material, such as NC sensitized nanocrystalline TiO₂The sun It can battery, concentrating solar battery, NC conducting polymer hybrid solar cell, p-i-n structure solar battery and/or optically focused Solar battery.

Fig. 5 shows the schematic diagram 500 of the hot carrier cooling of Auger process in semiconductor nanocrystal.In (a), lead to Cross makes hot carrier be cooled into possibility with interior Auger type energy transmission.Thermoelectron (point) can be cold by Auger type energy transmission But the hole state (such as CdSe NC) of close interval is arrived, then hot hole (circle) can pass through single phonon cascade emission (arrow Head) quick relaxation；(b) it shows phonon bottleneck effect and causes that there is the heat at a slow speed in the symmetrical conduction band and valence band of discrete energy level to carry Stream is cooling, and (c) shows and excited again by the hot carrier of band edge current-carrying intersubband auger recombination, and also referred to as Auger-adds Heat.

Substitution quick relaxation pathways (for example, in Fig. 5 with interior Auger type energy transmission ((a) in Fig. 5), atom Fluctuation and skin effect) inhibit the phonon bottleneck of this perception to be very effective under low carrier density.

Reduced dimension also generates competitive effect under higher carrier density: interband auger recombination.Latter Auger Excitation process (also referred to as Auger heats, as shown in (c) in Fig. 5) will make hot carrier cooling procedure slow down again.Therefore, nanometer In the interaction of the cooling complexity for being involved in different mechanisms of hot carrier in grade inorganic semiconductor.So far, even if making With the inorganic semiconductor nanocrystal of strong quantum confinement, hot carrier cooling is still extremely challenging to Yao Shixian at a slow speed.To the greatest extent Progress is achieved in terms of management opinion and materials synthesis, but actual hot carrier colloidal nanocrystals (NC) photovoltaic is still difficult to reality It is existing.Although the lowest excited energy level (1P in the PbSe quantum dot limited strongly_e-1S_e) have found it is slowly cold with interior thermoelectron But, but restricted thermoelectron must be separated with the hole with the especially well-designed more outer layers of epitaxial growth, to subtract The relaxation pathways of few above-mentioned competition.However, more outer layers can be such that subsequent charge-extraction complicates.Accordingly, it is possible to which it is necessary to design The cooling NC that two standards are extracted with effective charge of hot carrier at a slow speed can be met simultaneously.

Organic and inorganic lead halide perovskite semiconductor (such as MAPbX₃, wherein MA=CH₃NH₃, X=I, Br or Cl) recently Have become the main competitor in low-cost and high-performance solar battery.Recently to MAPbI under high carrier density₃In film Thermal phonon bottleneck effect observation show lead halide perovskite be also develop hot carrier solar battery promising time Material selection.Analog semiconductor nano science, an interesting problem are that the hot carrier cooling rate in halide perovskite is It is no further to be adjusted by restriction effect.Here, using the more different sizes of room temperature transient absorption (TA) spectrum (average half Diameter~2.5-5.6nm) colloid MAPbBr₃The cooling dynamics of hot carrier in NC (Fig. 6) and its body block film counterpart (Fig. 7) And mechanism.

Fig. 6 show according to various embodiments there is opposite (a) small size, (c) in size and (e) large-sized methyl Amine lead bromide perovskite (MAPbBr₃) nanocrystal (NC) typical transmission electron microscope (TEM) image, on the right of it be phase The size histogram (b, d, f) answered.Size distribution can be modeled with Gaussian Profile.Fig. 7 shows methyl amine lead bromide (MAPbBr₃) body block film (a) top view and (b) side view scanning electron microscope (SEM) image.

Fig. 8 shows (a) luminescence generated by light (PL) intensity (arbitrary unit or a.u.) to the curve graph of wavelength (nanometer or nm), Indicate the methyl amine lead bromide perovskite (MAPbBr according to various embodiments being dispersed in toluene₃) nanocrystal (NC) and Luminescence generated by light (PL) spectrum of body block film counterpart；(b) song of the absorbance (arbitrary unit or a.u.) to wavelength (nanometer or nm) Line chart indicates the methyl amine lead bromide perovskite (MAPbBr according to various embodiments being dispersed in toluene₃) nanocrystal (NC) and ultraviolet-visible (UV-vis) absorption spectrum of body block film counterpart；(c) 1s exciton energy E_1s(electron volts or eV) is right The curve graph of nanocrystal mean radius a (nanometer or nm) indicates methyl amine lead bromide perovskite according to various embodiments (MAPbBr₃) 1s exciton energy and radius relationship, and (d) X-ray diffraction (XRD) intensity (arbitrary unit or a.u.) To the curve graph of 2 θ of angle (as unit of spending), three kinds of various sizes of methyl amine lead bromide calcium according to various embodiments are indicated Titanium ore (MAPbBr₃) nanocrystal (NC) XRD diagram.

It is reported that MAPbBr₃Exciton Bohr Radius a_BFor~2nm.In view of NC radius (from~2.5 to 5.6nm, referring to Size distribution histogram in Fig. 6) it is greater than a_B, therefore NC is in weak restriction state.Therefore, as NC size reduces, the hair of NC Penetrating the small blue shift (from 525 to 517nm, Fig. 8 (a)) of generation may be due to weak restriction effect.In weak limitation, the first of NC Exciton resonance can write the relationship of NC radius a as:

Wherein E_g0It is the band-gap energy of not quantum confinement, and Section 2 represents limitation energy, μ is that electron-hole reduces matter Amount,E_bIt is exciton binding energy.Use the report value of above equation (1) and effective massThe ABSORPTION EDGE (referring to the line in Fig. 8 (c)) that NC can be reasonably fitted is to generate band gap E_g0~2.38eV, in conjunction with can be E_b~50meV, close to MAPbBr₃The report value of NC.These fitting results further demonstrate root According to the weak limitation in the perovskite NC of various embodiments.

The result shows that the MAPbBr of weak limitation₃NC (Fig. 8) is very promising hot carrier absorbent material, because They have higher hot carrier temperature and longer cooling time (with the typical perovskite under comparable photo-excitation conditions Body block film is compared).This may be attributed to their intrinsic phonon bottles under low carrier density and under high carrier density respectively Neck and Auger fuel factor.Importantly, by using molecular semiconductor as energy selectivity contact point, can at room temperature from MAPbBr₃NC film efficiently extracts hot carrier.

Fig. 9 A shows middle size methyl amine lead bromide perovskite nanocrystal in the solution according to various embodiments (MAPbBr₃NC) pseudo-colours transient absorption (TA) figure (upper figure, time (picosecond or ps) and the energy (electronics of (radius~4-5nm) Volt or eV) relational graph) and normalization transient absorption (TA) spectrum (following figure, normalized transmittance change Delta T/T are (electric to energy Son volt or eV) curve graph), wherein under low pump power density (left figure), electronics-that initial every nanocrystal averagely generates Hole is to for < N₀(the average carder density n of every nanocrystal volume of >~0.1_0avg~2.6 × 10¹⁷cm^-3), in high pumping function (right figure) < N under rate density₀(the n of >~2.5_0avg~6.5 × 10¹⁸cm^-3).Fig. 9 B shows MAPbBr₃The pseudo-colours table of body block film Show that ((following figure, normalized transmittance change Delta T/T is to energy for upper figure, time (picosecond or ps) and normalization transient absorption (TA) spectrum Measure the curve graph of (electron volts or eV)).Under low pump power density (left figure), the carrier density initially generated is n₀~ 2.1×10¹⁷cm³, (right figure) n under high pump power densities₀~1.5 × 10¹⁹cm³。

Fig. 9 A-B is shown respectively under low pump power density and high pump power densities, middle size MAPbBr₃NC (half Diameter~4.5nm) and MAPbBr₃The pseudo-colours TA figure and TA spectrum of body block film compare.For the sample of both types, due to shape State filing effect, curve graph/spectrum are shown in peak photobleaching outstanding (PB) that band gap nearby has high bandtail.In small size With similar result is also observed in size NC.

Figure 10 shows the time (picosecond or ps) to the curve graph of energy (electron volts or eV), indicates in the solution according to each (a) small size and (b) large-sized methyl amine lead bromide perovskite nanocrystal (MAPbBr of kind embodiment₃NC) pseudo-colours wink State absorb (TA) spectrum (by picosecond or ps as unit of time to the energy as unit of electron volts or eV).The excitation of 3.1eV light Afterwards, (left figure) electron-hole pair that initially every nanocrystal averagely generates is < N under low pump power density₀>~0.1, (right figure) < N under high pump power densities₀>~2.5.

For body block film sample, the high bandtail at the peak PB is originated from initial nonequilibrium carrier and passes through with carrier temperature T_cFor The elastic scattering of feature is (including in the electron-hole scattering under low pump power density and the load under high pumping energy density Stream-carrier scattering) quickly it is distributed in Fermi Dirac distribution.Therefore can by by the high bandtail of TA spectrum with Simple Boltzmann function exp (E_f-E/κ_BT_c) fitting extract T_c, wherein κ_BIt is Boltzmann constant, E_f It is quasi- Fermi energy.

For NC, in thermal energy k_BIn the case where T > > energy level separation delta E, discrete energy level can approximatively be considered as continuously.And have The conventional semiconductor NC limited by force is compared, and perovskite NC is likely to be at weak restriction state, and energy level is more closely spaced.Cause This, in the micro image of a single point, it is desirable to which (i.e. each NC has a pair of electricity below under low pump power density Son-hole to) effective electron-hole scattering (due to the Coulomb interactions enhanced under confined condition) and in high pumping Carrier-carrier scattering under power density can be such that quick non-thermal energy is distributed in 150fs to evolve into class Fermi-Di La Gram distribution.In macrograph, TA spectrum can be collected from the set of NC, and size distribution may cause non-uniform widthization (i.e. the overlapping TA spectrum from single NC).The continuous T A spectrum that all these characteristics correctly cause NC to gather is similar to ontology The TA spectrum of material.Therefore, the high bandtail of the TA spectrum of NC can also be described by Maxwell-Boltzmann distribution. High bandtail is shown in FIG. 11 and does not normalize the representative fitting of TA spectrum.Figure 11 shows (a) normalized transmittance Change Delta T/T indicates the methyl of the middle size in toluene according to various embodiments to the curve graph of energy (electron volts or eV) Amine lead bromide perovskite nanocrystal (MAPbBr₃NC) the normalization TA spectrum under different short delaing times, per nanocrystalline Electron-hole pair < N that body averagely generates₀>~0.1 (after the excitation of 3.1eV light)；And (b) (a) does not normalize transient absorption (TA) spectrum.(a) solid black line in uses the high bandtail of Maxwell-Boltzmann distribution Function Fitting.

From pseudo-colours TA curve and spectrum, it is apparent that for NC, the high bandtail at the peak PB (declines from index The kink subtracted in the spectrum that region starts starts, referring to Figure 11) it is more lasting than body block film much longer, show that carrier temperature is higher, Hot carrier cooling is slower.

The analysis and explanation of the TA spectrum of halide perovskite are documented in the literature.MAPbBr₃Perovskite is (blocky With nanocrystal) TA spectrum it is similar to previous research.Due to the state filling of the carrier at band edge, bleached by ground state (GSB) cause positive TA peak value (~2.3eV, as shown in Figure 11).High energy side at the peak GSB, first slope (more connect The slope of nearly GSB peak value) depend on influencing the ground state transition of its width and shape；And the second gentle incline of high bandtail (for example, in Figure 11 since~2.5eV) is to be distributed to generate by hot carrier.The negative part (photic absorption) of the high energy side It is as caused by the photic variation of the imaginary part of refractive index.And the negative part of GSB low energy side is attributed to band gap renormalization.

Hot carrier temperature is extracted by using the high bandtail of Boltzmann Function Fitting TA spectrum T_c.When the difference and κ between the energy and fermi level of carrier_B(E-E when T-phase is bigger_f>κ_BT), Fermi Dirac distribution Function can be described with exponential approximation, i.e. Maxwell-Boltzmann distribution:

Fermi Dirac distribution hot carrier energy > > E is approached with Maxwell-Boltzmann distribution_fIt is to extract heat to carry Flow sub- temperature T_cEffective and generally accepted practice.It can for intrinsic (untreated) perovskite NC and body block film, fermi level Between valence band and conduction band side (conduction band minimum~0.4eV (seeing below) for being lower than ultraviolet photoelectron spectroscopy (UPS) data). Therefore, the hot carrier of generation is possibly remote from Fermi energy (~1eV or more).Although fermi level can under strong light excitation Can be mobile (~0.1eV) gently towards band edge, but energy difference still may very big (i.e. E-E_f>>κ_BT (at room temperature~25meV).Cause This, can be used the high bandtail of Maxwell-Boltzmann distribution fitting TA spectrum to extract T_c。

Figure 12 shows carrier temperature (Kelvin or K) to the curve graph of time (picosecond or ps), indicates in various pumps Under the power density of Pu, the hot carrier temperature T of middle sized nanocrystals (NC) and body block film according to various embodiments_cTime It develops: initial light activated hot carrier density n₀Electron-hole pair < N that (body block film) and every NC are averagely generated₀>, wherein<N₀ >=J σ, wherein J is pump power density, and σ is absorption cross-section.

Figure 13 shows (a) luminescence generated by light (PL) intensity (arbitrary unit or a.u.) to the curve of time (nanosecond or ns) Figure, indicates middle size methyl amine lead bromide perovskite nanocrystal (MAPbBr according to various embodiments₃NC) swash in 3.1eV light The pump power density for giving time resolution luminescence generated by light (PL) relies on；(b) transient photoluminescence (PL) intensity (arbitrary unit or A.u.) to the curve graph of pump intensity (micro- joule/square centimeter or μ J cm^-2), indicate three kinds of differences according to various embodiments The MAPbBr of size₃NC normalizes PL intensity to the relational graph of pump power density at time of measuring Δ t=4ns；And (c) Probability (percentage or %) is occupied to the curve graph of the quantity of the electron-hole (e-h) pair of each NC according to various embodiments.

Occupy the Poisson distribution of rate based on initial photon in NC, NC include i to e-h pairs of probability byIt provides, wherein < N₀>=J σ be each NC initially generated e-h pairs of par (J be pumping Power density, σ are the absorption cross-sections of NC).Delay time (for example, auger recombination) more compound than multiple carrier after light excitation is long When much, NC may be mainly compound with single exciton emission, therefore later period PL intensity may be with the occupation probability of light activated NC It is proportional, beFigure 13 (b) display pumps function when completing multiple carrier compound tense The normalization when pump power density of the time resolution luminescence generated by light (PL) of the relevant TRPL of rate density relies on time t=4ns, And PL intensity represents transmitting NC only with an electron-hole pair.By the way that data are fitted toEquation is (real Line), the σ of NC can be obtained.For NC from small to large, the σ of fitting is respectively 8.5 ± 0.5 × 10^-15,3.2±0.2×10^-14 With 6.8 ± 0.3 × 10^-14cm²。

In order to be compared with body block film, it can also determine the average carder density of every NC volume in NC, be defined as n_0avg=N₀/V_NC, wherein V_NCIt is NC volume.For NC, when excitation starts < N₀The maximum T of >~0.1_cIt can be about 1700K, this It is about 4 times of body block film sample with comparable carrier density.Lesser T in the latter_cIt is attributable to the super of hot carrier It is fast cooling, occur in the time scale of the temporal resolution much shorter measured than TA.

It should be noted that the complicated interaction of hot carrier cooling time is caused by several factors: (i) pump energy is (i.e. The excess energy of carrier --- cause hot carrier lifetime longer in general, excess energy is higher)；(ii) initial hot carrier is close It spends (i.e. usual carrier density is higher to cause hot carrier lifetime longer)；And/or the energy under (iii) particular thermal carrier temperature Amount loss rate (that is, the rate of energy loss that usual hot carrier temperature gets over low yield life is smaller).Therefore, it is necessary to suitably pay attention to document The value of middle report carries out fair comparison.The more discussion compared about the hot carrier lifetime between different materials can be below " hot carrier lifetime " part in find.

In addition, the service life is cooled down with the hot carrier of different materials more easily more reported in the literature in order to become apparent from, The hot carrier as described herein cooling service life can be defined as being cooled to the time interval of 600K from pulse excitation to hot carrier. The temperature is used as benchmark, because previous theoretical calculation is it has been shown that for T_c> 600K, in the absorber band gap of wide scope It there will still likely be apparent hot carrier transfer efficiency (i.e. > 40%).

In view of these factors, for compareing MAPbBr₃Body block film, obtains n₀~2.1-15 × 10¹⁸cm^-3Under from < The hot carrier of 0.1ps to the 0.8ps cooling service life.These service life in similar n₀With excite under the excess energy of 0.7eV MAPbI₃The service life of film is identical；But the hot carrier of the height excitation of than twice excess energy (~1.44eV) is short.Value It obtains it is noted that MAPbBr₃NC is in similar n_0avgUnder can show 1-2 quantity longer than perovskite body block film control sample The hot carrier of grade is cooling service life (as shown in figure 14).First according to various embodiments is compared in table 1400 shown in Figure 14 Base amine lead bromide perovskite nanocrystal (MAPbBr₃NC), methyl amine lead bromide perovskite body block film and it is reported in the literature its The property of his material.As previously mentioned, the hot carrier cooling service life can be defined as being cooled to from pulse excitation to hot carrier The time interval of 600K.600K may be used as benchmark, because previous theoretical calculation is it has been shown that for T_c> 600K, in wide model It there will still likely be apparent hot carrier transfer efficiency (i.e. > 40%) in the absorber band gap enclosed.TA refers to " transient absorption ", TRPL refers to " time resolution luminescence generated by light ".

Figure 15 shows three kinds of various sizes of methyl amine lead bromide perovskite nanocrystals according to various embodiments (MAPbBr₃NC) and carrier temperature (Kelvin or K) of the body block film after the excitation of 3.1eV light is to time delay (picosecond or ps) Curve graph, wherein (a) (is equivalent in NC < N under low pump power density₀>~0.1, n in body block film₀~2.1 × 10¹⁷cm³), (b) (< N is equivalent in NC under high pump power densities₀>~2.5, n in body block film₀~1.5 × 10¹⁹cm³).Greatly The service life of size NC can be about 40 times than the service life of body block film sample, and wherein body block film is with the current-carrying of almost high an order of magnitude Sub- density 1.5 × 10¹⁹cm^-3It is excited.For example, for having < N₀>~2.5 (or n_0avg~3.5 × 10¹⁸cm^-3) large scale NC, hot carrier cooling service life are~32ps (Figure 15).In fact, MAPbBr₃The hot carrier of the NC cooling service life may Service life more cooling than the hot carrier of other semiconductor bodies and nano material is much longer.With reference to Figure 14, for GaAs film, report The cooling service life be~2ps, carrier density be~6.0 × 10¹⁸cm^-3, excess energy 1.7eV；For CdSe nanometer rods, The cooling service life of report is~0.8ps, and carrier density is~5.5 × 10¹⁸cm^-3, excess energy 1.1eV.MAPbBr₃NC can Comparable to the more long-life of 18ps, in comparable carrier density 6.5 × 10¹⁸cm^-3Under with much lower excess energy~0.7eV Excitation.

In order to distinguish MAPbBr₃Slower hot carrier cooling mechanism in NC observes the low pumped Relaxation Kinetics given. For < N₀>~0.1 is based on Poisson distribution, with an e-h to the NC (Figure 13) of excitation up to 10%.There is no band edge load from NC The rapid decay of stream can be seen that (Figure 16), and under so low carrier density, multiparticle is compound to be can be ignored.

Figure 16 shows normalized transmittance change Delta T/T to the curve graph of time (picosecond or ps), indicates in the solution Methyl amine lead bromide (a) body block film, (b) small size nanocrystal (NC) according to various embodiments, (c) according to various implementations The middle sized nanocrystals (NC) of example and (d) macro nanometer crystal (NC) according to various embodiments are respectively in high pump power Under density and low pump power density, in the photic bleaching kinetics of normalization of band edge detection；And (e) basis in the solution The transient absorption of the middle sized nanocrystals (NC) of various embodiments and Spincoating of nanocrystal (NC) film according to various embodiments (TA) dynamics compares；And (f) small size methyl amine lead bromide nanocrystal according to various embodiments in the solution (NC) it is relied in the pump power density of the bleaching kinetics of band edge detection.(f) illustration in Figure 16 was shown in the long period Under subtract the auger recombination component extracted after single exciton relaxation.Light excitation energy is about 3.1eV.

Therefore, the hot carrier Relaxation Mechanism under low pump excitation can represent the intrinsic property of material, and can not It is influenced by the external effect of such as multiparticle auger recombination etc.

Under low pump power density, with the increase of NC size, T_cCan quickly be decayed (Figure 15).Figure 17 shows (a) rate of energy loss (every picosecond of eV ps of electron volts^-1) to the curve graph of carrier temperature (Kelvin or K), it indicates according to various The methyl amine lead bromide perovskite nanocrystal (MAPbBr of embodiment₃NC) (wherein < N₀>~0.1) and methyl amine lead bromide calcium titanium Mine (MAPbBr₃) body block film (wherein n₀~2.1 × 10¹⁷cm^-3) carrier temperature T_cTo the rate of energy loss of hot carrier Relational graph；(b) normalized transmittance change Delta T/T indicates according to various embodiments the curve graph of time (picosecond or ps) Colloid methyl amine lead bromide perovskite nanocrystal (MAPbBr₃NC) and body block film is under low carrier density, band edge detection Normalize bleaching kinetics；And (c) rise time (femtosecond or fs)/limitation energy (electron volts or eV) curve graph, it indicates Methyl amine lead bromide perovskite nanocrystal (MAPbBr₃NC) (black solid square), body block film (light closed square) (partial size Indicated by film thickness) and cadmium selenide nano crystal (CdSe NC) (filled circles) in band edge bleaching rise time size rely on, And MAPbBr₃The size of quantum confinement energy relies in NCs (hollow square) and CdSe NC (open circles).Error line indicates Standard error.Figure 17 (a)-(c) light excitation energy is 3.1eV.It is right that Figure 18 shows raman scattering intensity (arbitrary unit or a.u.) Wave number (per cm or cm^-1) curve graph, indicate the methyl amine lead bromide perovskite nanocrystal for preparing according to various embodiments (MAPbBr₃NC) the Room temperature Raman spectra of drop coating on the glass substrate.Peak is originated from LO phonon.The Raman Measurement shown in Figure 18 It can be seen that MAPbBr₃The cooling available phonon model of hot carrier is located at about 150cm in NC^-1(it is appointed as Pb-Br key Stretching) and 300cm^-1(it may be from 150cm^-1The torsional mode of second order and/or MA cation.

The solid line of Figure 17 (a) indicates the numerical fitting of LO- phonon model.Arrow indicates the maximum T that body block film obtains_c.Figure Illustration in 17 (a) shows the representative TEM image of small size (S), middle size (M) and large scale (L) perovskite NC.Figure 17 (b) solid line in is mono-exponential fit.Illustration in Figure 17 (b) is shown in the symmetrical conduction band and valence band with discrete energy level Phonon bottleneck induction the cooling schematic diagram of slow hot carrier.

For all three NC, the rate of energy loss J of each carrier_r(-1.5κ_B dT_c/ dt) it can be in 0.6-0.3eV ps^-1In the range of slowly reduce, until T_cReach~700K (Figure 17 (a)), is lower than the value, J_rDecline several orders of magnitude, until T_c Close to lattice temperature.This cooling trend is similar to the cold of body block film sample and other bulk inorganic semiconductors and nanostructure But trend.Here, it is initially quickly cooled down (i.e. higher cooling rate) and is attributable to Carrier Coupling to longitudinal optics (LO)-sound Son establishes thermal balance between LO phonon group and hot carrier.Compare different NC, the initial J of small size NC_rCompare large scale NC is small~2 times (showing that carrier-phonon interaction in the former is weaker).Then by longitudinal optical phonon (LO phonon) and Thermal balance between acoustical phonon determines the slower cooling (i.e. in Figure 17 (a)~300-500K) close to the hot carrier of band edge.

Rate of energy loss, fitting are fitted by using LO- phonon interaction model (referring to following LO- phonon model) τ_LO(feature LO- phonon damping time) increases with the reduction of NC dimension (referring to Figure 17 (a)), this can be quantum confinement It reduces optical phonon relaxation and positive evidence is provided.This is the feature of phonon bottleneck effect, therefore it is cooling to delay hot carrier.Though Right NC is in weak restriction state, and limitation energy is about~15-60meV, but the theoretical paper of several early stages shows even if this Level spacing is only that can also be nevertheless suffered under the weak limited condition of several meV by the carrier relaxation that phonon interaction mediates It is serious to hinder.This is because the weak power dissipation of limitation and longitudinal optics (LO) phonon that energy and the conservation of momentum are applied, They cause phonon bottleneck jointly.In addition, the acoustical phonon temperature (Ta) of all three NC samples is equivalent to~310K, with room temperature Under lattice temperature it is close, this is strongly suggested that, the cooling deceleration of hot carrier may be less likely to be drawn by acoustical phonon bottleneck It rises.

Band edge bleaching stacking method is also used for illustrating hot carrier cooling property.In addition to the high bandtail at the fitting peak PB is to explain Except the method for bright hot carrier cooling characteristics, another method is the photoexcitation carrier that detection is higher than band edge with interior relaxation Henan.This can be realized by monitoring band edge bleaching accumulation, because compound (~the ns) of band edge carrier is than it with interior relaxation mistake Journey is (from several much slower to tens ps).Later approach carries commonly used in the heat in the strong limitation quantum colloidal semiconductor NC of research Subdynamics are flowed, because the overlapping PB band from discrete energy level makes the hot carrier distribution for solving them extremely challenging.Afterwards A kind of method can be used for hot carrier cooling and Conventional inorganic semiconductor NC (such as CdSe NC) of fair relatively perovskite NC Hot carrier is cooling.

Figure 17 (b) shows the normalization TA spectrum of perovskite sample, with similar excess energy under low carrier density It is detected at the peak its band edge PB after measuring light excitation.Each banking process is fitted single index Growth Function, to generate the rise time (τ_rise).Band edge bleaching, which rises, to be occurred in the time scale of subpicosecond grade, and smaller as the reduction of NC size becomes slower Perovskite NC lesser J_rSlower hot carrier temperature damping (Figure 15) is consistent., it is surprising that perovskite NC The trend shown and the trend of CdSe NC it is completely opposite (across arriving weak quantum confinement region by force --- Figure 17 (c) and scheme 19)。

Figure 19 shows (a) normalized transmittance change Delta T/T to the curve graph of time (picosecond or ps), indicates have not Power is bleached in colloid CdSe NC (showing in the legend) normalization that band edge detects under low pump power density with diameter It learns；And (b) time (picosecond or ps) to the curve graph (electron volts or eV) of energy, indicates most primiparity under low pump power density Life < N₀>~0.1 (left side), under high pump power densities<N₀>~2.5 (right side).Light excitation energy is 3.1eV.Reality in Figure 19 (a) Line is single index growth fitting curve.Illustration in Figure 19 (a) is schematically shown to be carried by the heat of Auger type energy transmission Flow sub- cooling procedure.

In addition, the perovskite NC rise time can also be longer.With the reduction of CdSe NC, hot carrier is cooling faster, this Consistent with previous report, this is attributed to the Auger type energy transmission from thermoelectron to intensive hole state.As a result it clearly illustrates, This Auger pass through mechanism being present in Conventional inorganic semiconductor NC can be suppressed naturally in perovskite NC.About The schematic energy level diagram (Fig. 5) of CdSe NC, a possible reason may be perovskite NC shown in the illustration of Figure 17 (b) Electrons and holes symmetry energy dispersion and small effective mass.The other factors such as resurfacing, surface defect, atom fluctuation It may also lead to hot carrier cooling to become faster as inorganic semiconductor size is reduced (for example, in the IV-VI of quantum confinement In semiconductor PbSe, there is identical and small electrons and holes effective mass).Therefore, perovskite NC low-defect-density (with MAPbBr₃The high PL quantum yield (~80%) of NC is consistent) another reason for being also likely to be this idiosyncratic behavior is (that is, intrinsic Phonon bottleneck effect).These neodoxies (under low pump excitation) cooling to the slow hot carrier of perovskite colloid NC can It can challenge the conventional wisdom of conventional semiconductors NC.

These perovskites NC also shows unique hot carrier cooling characteristics under high pumping excitation.Figure 20 is shown (a) rate of energy loss (every picosecond of electron volts or eV ps^-1) to the curve graph of carrier temperature (Kelvin or K), it indicates according to each The methyl amine lead bromide perovskite nanocrystal MAPbBr of kind embodiment₃NC(<N₀>~2.5) and MAPbBr₃Body block film (n₀~ 1.5×10¹⁹cm^-3) rate of energy loss and carrier temperature T_cRelationship；(b) service life, (picosecond or ps) was to nanocrystal volume (cubic nanometer or nm³) curve graph, illustrate perovskite nanocrystal (NC) volume and auger recombination according to various embodiments The relationship in service life and hot carrier cooling time, and (c) normalize hot carrier concentration n_hotTo the curve of time (picosecond or ps) Figure indicates the normalized hot carrier decay under different pump power densities according to various embodiments.Reality in Figure 20 (a) Line indicates the LO- phonon model under low carrier density.Dotted line in Figure 20 (b) shows square of nanocrystal (NC) volume The relationship of root and service life, and the hot carrier of cut line band edge carrier auger recombination is excited again (also referred to as Auger Heating), error line indicates standard error.Solid line in Figure 20 (c) is double exponential damping fittings.The excitation of Figure 20 (a)-(c) light Energy is 3.1eV.Body block film thickness about 240nm.

Figure 20 (a) shows three kinds of various sizes of NC (< N₀>~2.5) and body block film sample (n₀~1.5 × 10¹⁹cm^-3) Between rate of energy loss and carrier temperature comparison trend.For NC and body block film, by carrier-LO- phonon phase interaction It may be almost unrelated with carrier density with the initial hot carrier cooling of control.The conclusion can be obtained from following: (i) be not With the initial rapid decay T under carrier density_cAlmost the same (Figure 12), and the initial energy of (ii) at a temperature of high carrier Amount loss rate is similar under high carrier density (Figure 17 (a) and Figure 20 (a)) in low carrier density.For body block film, The extension (Figure 12) of 600K or less hot carrier lifetime and J_rSlight deviations (line in Figure 20 (a)) with LO phonon model may It is since " thermal phonon bottleneck effect " (is usually observed in bulk inorganic semiconductors, report is used for MAPbI recently₃Film). This is attributable to LO phonon damping caused by being heated by the part of acoustic model and reduces.This hypothesis can pass through high pump power The higher acoustical phonon temperature T of 350K under density_aTo support.

Figure 21 is rate of energy loss (every picosecond of electron volts or eV ps^-1) to the curve of carrier temperature (Kelvin or K) Figure indicates methyl amine lead bromide (MAPbBr₃) hot carrier energy of the body block film under low carrier density and high carrier density Amount loss rate and carrier temperature T_cRelationship.Solid line indicates fitting (such as following " the LO- Phonons of digital water transfer formula (3) Shown in type " part).The LO phonon lifetime τ being fitted under low carrier density and high carrier density_LOWith acoustics temperature T_aRespectively 150 ± 20,280 ± 20fs and 305 ± 10 and 350 ± 10K.

However, for NC, as shown in Figure 20 (a), although the J of NC_r(<N₀>~2.5) initially abided by a temperature of high carrier LO- phonon model is followed, but they and LO- phonon model have very big difference, because hot carrier group is cooled to 1500K or less.It is right In temperature range < 1000K, when carrier density is from < N₀(Figure 17 (a)) increases to<N for>~0.1₀(Figure 20 (a)), J when >~2.5_r Strongly reduce several orders of magnitude.For example, in < N₀J when >~0.1, under 700K_rAbout 0.3eV ps^-1, and in < N₀When >~2.5 For~0.008eV ps^-1.In addition, in < N₀>~2.5, when carrier temperature<1200K, J_rReduce with the increase of NC size. All these features show that hot carrier cooling mechanism, the mechanism only account under high carrier density leading at a slow speed in the presence of another kind Status, it is believed that this is Auger heating mechanism, since it is known that increasing since carrier-carrier interacts, Auger It is compounded in limited semiconductor N C and strongly enhances.Therefore, by the auger recombination of band edge carrier, the hot carrier of relaxation ( At band edge) there is certain probability to be remotivated to more upper state (illustration of Figure 20 (b)).

Figure 20 (c) display, the calculating concentration (n of the hot carrier of different size of NC_hot(t)) with double exponential manner relaxation, Rapid decay occurs in 1ps and slower decay occurs in tens ps --- it is similar to hot carrier temperature (Figure 12 and figure 15).Rapid decay is attributable to carrier-LO- phonon interaction.In addition, fitting slow-decay service life n_hot(t) with 1/3 Auger lifetime τ_Aug(i.e. τ_hot~τ_Aug/ 3 --- Figure 20 (b)) exact matching, see also hereafter " Auger heating model " part).Example Such as, the slower decay service life of small size NC is fitted to~12ps, very close τ_AugIt is the 1/3 of 38ps.Experimental data with include Russia What the good uniformity between the naive model for effect of having a rest can forcefully confirm further to postpone under high carrier density The main contributions of Auger heating during hot carrier is cooling.Given τ_Aug~√ (V_NC) and slow hot carrier lifetime τ_hot~τ_Aug/ 3, Russia Have a rest hot carrier cooling service life of induction can depend on NC volume (Figure 20 (b)) with sublinear.Although Auger heating leads to heat Carrier cooling rate slows down, and is conducive to hot carrier extraction, but is further noted that auger effect may reduce on the contrary Carrier density.Therefore, it in the application of optically focused hot carrier solar battery, may be needed under high pump power densities flat Weigh hot carrier lifetime and carrier loss.

Other than hot carrier cooling at a slow speed, the feasibility that effective hot carrier is extracted may be hot carrier solar energy Another challenge of battery.Hot carrier may be needed quickly to extract with limit energy losses, wherein competing It is present between extraction rate and cooling rate, rather than recombination rate.In view of MAPbBr₃The hot carrier of film estimation expands Dissipate length be~(seeing below, " hot carrier diffusion length is estimated by 16-90nm (depend on hot carrier lifetime and diffusion coefficient) Calculate "), therefore it is technically feasible for extracting hot carrier.It is demonstrated herein from 1,2- dithioglycol (EDT) processing MAPbBr₃Effective thermoelectron of NCs (EDT-NC) to 4,7- diphenyl -1,10- phenanthroline (Bphen) extracts.

Figure 22 shows curve graph of the photoelectron intensity (counting per second or cts/s) to energy (electron-volt or eV), table Show root (a) 1,2- dithioglycol (EDT) processing on tin indium oxide (ITO) substrate and that (b) is handled through the EDT of after annealing According to the methyl amine lead bromide (MAPbBr of various embodiments₃) nanocrystal (NC) film, and (c) 7- diphenyl -1,10- phenanthroline (Bphen) ultraviolet photoelectron spectroscopy (UPS) of film.Maximum price band (VBM) can linearly be extrapolated to background by valence band forward position Intensity determines, is 1.9 ± 0.1,2.3 ± 0.1 and 2.9 ± 0.1eV respectively in Figure 22 (a)-(c).

Can choose Bphen as thermoelectron extract material because the molecular semiconductor have high electron mobility and Conduction band minimum (CBM) the higher lowest unoccupied molecular orbital (LUMO) of NC with the EDT processing than us is (referring to figure 22, UPS measurements), only imply that Bphen (3A referring to fig. 2) can be injected in the hot carrier on band edge with enough excess energies.

Figure 23 A is flat rubber belting energy diagram (vertical axis electron-volt or eV), to illustrate from perovskite according to various embodiments The thermoelectron of nanocrystal to 7- diphenyl -1,10- phenanthroline (Bphen) extracts and the cooling approach of the thermoelectron of competition.It can be with The conduction band minimum (CBM) (or LUMO level) and valence band minimum for determining NC (or Bphen) are measured from UPS and ultraviolet-visible (VBM) (or highest occupied molecular orbital (HOMO) is horizontal).Figure 23 B shows 1,2- dithioglycol according to various embodiments (EDT) atomic force microscope (AFM) image of nanocrystal (NC) film handled.Figure 23 C is 1,2- according to various embodiments Nanocrystal (NC)/7- diphenyl -1,10- phenanthroline (Bphen) duplicature scanning electron of dithioglycol (EDT) processing is aobvious Micro mirror (SEM) image.Scale bar is 100nm.

Figure 23 D is curve graph of the normalized transmittance change Delta T/T to energy (electron-volt or eV), is indicated according to various Embodiment has the 1,2- second of (continuous lines)/about 35nm thickness without (dotted line) 7- diphenyl -1,10- phenanthroline (Bphen) Nanocrystal (NC) film of two mercaptan (EDT) processing (< N after 3.1eV photoexcitation₀> normalization transient absorption about 0.1) (TA) spectrum.The illustration of Figure 23 D, which is shown, does not normalize transient absorption (TA) spectrum under 0.8ps.Figure 23 E is according to various implementations Nanocrystal (NC) film of 1,2- dithioglycol (EDT) processing of example and the nanocrystal of 1,2- dithioglycol (EDT) processing (NC) film/7- diphenyl -1,10- phenanthroline (Bphen) duplicature hot carrier temperature under different pump power densities (is opened Your text or K) to the curve graph of delay time (picosecond or ps).Dotted arrow indicates initial hot carrier temperature after Bphen layers of addition The reduction of degree shows that effective thermoelectron extracts.

Figure 23 F is extraction efficiency η_hot(percentage or %) to the curve graph of thermoelectron excess energy (electron-volt or eV), Indicate nanocrystal (NC)/diphenyl -1 7- of 1,2- dithioglycol (EDT) processing of about 35nm thickness according to various embodiments, The pump energy of thermoelectron extraction efficiency relies in 10- phenanthroline (Bphen) duplicature.The illustration of Figure 23 F, which is shown, have/not to be had There is the EDT-NC film of the about 35nm thickness of Bphen (< N after 2.5eV photoexcitation₀TA is not normalized under > about 0.1) 0.8ps Spectrum.Figure 23 G is extraction efficiency η_hot(percentage or %) indicates according to various implementations the curve graph of thickness (nanometer or nm) Nanocrystal (NC)/7- diphenyl -1,10- phenanthroline (Bphen) duplicature and body of 1,2- dithioglycol (EDT) processing of example The calcium of block film/7- diphenyl -1,10- phenanthroline (Bphen) duplicature thermoelectron extraction efficiency after the excitation of 3.1eV pump energy Titanium ore film thickness relies on.Illustration show with/without Bphen about 140nm thickness EDT-NC film 3.1eV photoexcitation it (< N afterwards₀TA spectrum is not normalized under > about 0.1) 0.8ps.Error bars in x-axis indicate the excess energy measured in Figure 23 F and The uncertainty of the thickness of sample measured in Figure 23 G, the error bars in y-axis indicate the uncertain of the extraction efficiency of measurement Property.

Figure 24 (a) shows transmissivity (arbitrary unit or a.u.) to wave number (per cm or cm^-1) curve graph, indicate root According to methyl amine lead bromide nanocrystal (MAPbBr prepared by various embodiments₃NCs), 1,2- dithioglycol (EDT) is handled In decaying total reflection-Fu of nanocrystal (EDT-NC) and the 1,2- dithioglycol nanocrystal (Ann-EDT-NC) of 70 DEG C of annealing Infrared (ATR-FTIR) spectrum of leaf transformation；And light emitting intensity (arbitrary unit or a.u.) is to combination energy (electron-volt or eV) Curve graph, indicate that (b) unannealed according to various embodiments and 1,2- dithioglycol (EDT) of (c) 70 DEG C of after annealings handled Sulphur (S) the 2p x-ray photoelectron spectroscopy (XPS) of nanocrystal (EDT-NC) film.S 2p can on the surface NC deconvolution Cheng Wei In conjunction with mercaptan and combination mercaptides (referring to the discussion part of FTIR and XPS analysis about ligand exchange).

Bphen has narrow electronic bandwidth, this can be close to the choosing of energy needed for hot carrier solar battery Selecting property contact point.EDT processing can be used for being replaced the oil of the length being present on the prepared surface NC and high-insulation with mercaptides Sour ligand (referring to fig. 2 the ATR-FTIR in 4 and XPS measuring and about the FTIR of ligand and the part of XPS analysis), more to have Effect ground and Bphen electron coupling in NC film (as shown in the TEM image in Figure 25, NC filling is closer after processing).Figure 25 shows The untreated middle size methyl amine lead bromide nanocrystal (MAPbBr of (a) according to various embodiments out₃NC) the atom of film Force microscope (AFM) image, and (b) the methyl amine lead bromide nanocrystal of 1,2- dithioglycol processing according to various embodiments (the MAPbBr of EDT processing₃NC) representative transmission electron microscope (TEM) image.Figure 26 shows (a) according to various embodiments Middle size methyl amine lead bromide nanocrystal (MAPbBr₃NC) film, (b) 1,2- dithioglycol processing according to various embodiments Nanocrystal the NC of processing (EDT) film, and (c) nanocrystal film of 1,2- dithioglycol processing according to various embodiments/ 7- diphenyl -1,10- phenanthroline (NC film/Bphen of EDT processing) duplicature (left figure, < N under low pump power density₀>~ 0.1) and high pump power densities under (right figure, < N₀>~2.5) pseudo-colours transient absorption (TA) spectrum.After the excitation of 3.1eV light, The high bandtail of EDT-NC/Bphen may be reduced.

It can by the thermoelectron extraction of the spin coating EDT-NC film (AFM and SEM image in 3B-C referring to fig. 2) of Bphen With significantly reducing of instantaneously occurring of the high bandtail by the TA spectrum of EDT-NC/Bphen duplicature come verify (3D referring to fig. 2, Pseudo-colours TA spectrum in Figure 26 and about " influence of the Trions to hot carrier in photoelectricity NC and NC film " part).

For the EDT-NC film of~35nm thickness, after Bphen layers of addition, initial T_cUnder low pump intensity from~ 1300K is cooled to 450K, after light excitation~200fs under high pumping intensity be cooled to 800K (Figure 23 E), table from~1800 Bphen can be injected in the bright carrier with higher-energy and temperature.Conduction band minimum between EDT-NC and Bphen and LUMO offset, can extract the hot carrier (Figure 27) with excess energy >=0.2 ± 0.1eV.Figure 27 shows energy diagram (y Axis: the energy as unit of electron-volt or eV), it indicates by ultraviolet photoelectron spectroscopy (UPS) and ultraviolet-visible (UV-VIS) light 1,2- dithioglycol-nanocrystal (EDT-NC) film and 7- bis- of non-annealing according to various embodiments, annealing that spectrometry determines The case where flat rubber belting energy level of phenyl -1,10- phenanthroline (Bphen) is aligned, and is extracted for thermoelectron is illustrated.The thermoelectricity of extraction Excess energy (the E of son_hot-excess) can be determined by the band offset between the conduction band minimum of NC and the LUMO of Bphen.

In view of the increased diffusion coefficient of hot carrier (referring to the part estimated about hot carrier diffusion length) and NC Between ultrafast hot carrier jump (in tens fs), thermoelectron may be by the electrons spread inside NC and at the interface NC The jump at place and inject Bphen.Thermoelectron transfer driving force can be between hot carrier energy and LUMO energy relative to The energy difference of Fermi energy, as shown in fig. 23 a.For organic molecule, the big density of states is typical.Therefore, efficiently The forceful electric power between big acceptor state density and Bphen and NC that hot carrier transfer is attributable in the lumo energy of Bphen Son coupling.Other control experiment proves that Bphen may be that the unique of hot carrier is extracted from the NC in EDT-NC/Bphen Approach, and exist in Bphen the electric charge carrier of transfer referring to the control experiment of transfer " verifying hot carrier " and " the PIA signal of electric charge carrier is shifted in Bphen " part.

Figure 28 (a) shows absorbance (arbitrary unit or a.u) to the curve graph of wavelength (nanometer or nm), indicates in glass On Bphen film linear absorption spectrum；(b) negative transmissivity variation is normalized --- song of the Δ T/T to wavelength (nanometer or nm) Line chart indicates that 7- diphenyl -1,10- phenanthroline (Bphen) (300nm pump intensity is 20 μ J cm^-2；400nm pump intensity is 40μJ cm^-2), (400nm pump intensity is 15 μ J cm for perovskite nanocrystal (NC) according to various embodiments^-2) and according to 1,2- dithioglycol nanocrystal/7- diphenyl -1,10- phenanthroline (EDT-NC/Bphen) (400nm pumping of various embodiments Intensity is 15 μ J cm^-2) 2ps after excitation negative transient absorption spectra；(c) time, (picosecond or ps) was to wavelength (nanometer or nm) Curve graph, indicate according to various embodiments 1,2- dithioglycol processing nanocrystal/7- diphenyl -1,10- phenanthroline (EDT-NC/Bphen) duplicature pump intensity is 15 μ J cm^-2Light activated pseudo-colours transient absorption (TA) light of 400nm Spectrum；(d) variation of negative transmissivity is normalized --- Δ T/T is light activated with 300nm to the curve graph of time (picosecond or ps) Bphen, and nanocrystal/7- diphenyl -1,10- phenanthroline (EDT- of 1,2- dithioglycol processing according to various embodiments NC/Bphen) duplicature 400nm optical pumping, the negative transient absorption spectra of the normalization detected at 1300nm.Solid line is two fingers The matched curve of number attenuation function.

It is worth noting that, we have also observed that EDT-NC/Bphen duplicature (wherein only selective excitation NC) and Bphen (more than band gap exciting) similar near-infrared (NIR) photoinduction hydrophilicity (PIA) signal (referring to fig. 28 and " Bphen transfer The PIA signal of the electric charge carrier of shifting " part), this may be as caused by the Photogenerated Radicals anion in Bphen.Therefore, Photoinduction hydrophilicity (PIA) signal in EDT-NC/Bphen duplicature is attributable to the hot carrier group shifted from NC to Bphen (Figure 28 (b)).Nevertheless, another alternative interpretations may be excited caused by hot energy transmission from NC to Bphen it is single Weight state absorbs.

Can based on after add Bphen~0.8ps at the reduction percentage of band end light bleaching strength estimate thermoelectricity Sub- extraction efficiency (η_hot) (because reduced band edge bleaching strength can be attributed to hot carrier when thermoelectron relaxes towards band edge Extraction).For the EDT-NC/Bphen duplicature of~35nm thickness, in < N₀The η calculated under >~0.1 and 2.5 pump intensities_hot Respectively~72% and~58%.Higher pump power density decline much lower thermoelectron injection efficiency may be due to from The antielectron of Bphen to NC, which shifts, to be increased, and the antielectron transfer time of estimation is~80ps (Figure 29 and " antielectron transfer time Estimation " part).

Figure 29 is normalized transmittance change Delta T/T to the curve graph of time (picosecond or ps), is indicated according to various implementations What nanocrystal (EDT-NC) film and 1,2- dithioglycol according to various embodiments of the 1,2- dithioglycol processing of example were handled Nanocrystal/7- diphenyl -1,10- phenanthroline (EDT-NC/Bphen) duplicature (< N under (a) low pump power density₀>~ 0.1) and (b) high pump power densities under (< N₀>~2.5) the light activated normalization band edge bleaching kinetics of 3.1eV.Figure 30 A is Normalized transmittance change Delta T/T indicates the tool annealed according to various embodiments to the curve graph of energy (electron-volt or eV) There are (continuous lines) and the 1,2- dithioglycol for not having (dotted line) 7- diphenyl -1,10- phenanthroline (Bphen) extract layer to handle Size methyl amine lead bromide nanocrystal (MAPbBr in (EDT processing)₃NC) film under low pump power density < N₀>~0.1 Normalize transient absorption spectra.The illustration of Figure 30 A, which is shown, does not normalize TA spectrum, η under 0.8ps_hotIt is determined as~83%.Figure 30B is carrier temperature (Kelvin or K) to the curve graph of time (picosecond or ps), indicates two samples according to various embodiments Relationship of this extraction hot carrier temperature to delay time.Figure 30 C is normalized transmittance change Delta T/T to energy (electronics Volt or eV) curve graph, indicate have (continuous lines) and do not have (dotted line) 7- diphenyl -1,10- phenanthroline (Bphen) mentions Take the methyl amine lead bromide (MAPbBr of layer₃) body block film (~240nm thick) is 2 × 10 under low pump power density¹⁷cm^-3Normalizing Change transient absorption (TA) spectrum.The illustration of Figure 30 C, which is shown, does not normalize TA spectrum, η under 0.8ps_hotIt is determined as~16%.Figure 30D shows the carrier temperatures (Kelvin or K) of two samples according to various embodiments to time delay (picosecond or ps) Curve graph.Light excitation energy is 3.1eV.

In view of the gap (Figure 23 B afm image) in NC film, some Bphen molecules can penetrate the upper layer of NC film, this Hot carrier can be further increased by increasing the interface NC/Bphen in relatively thin NC film/Bphen duplicature to extract Efficiency.In addition, rear heating (for example, 5 minutes at 70 DEG C) EDT-NC of appropriateness can not only further enhance electronics coupled (ginseng See the XPS spectrum in Figure 24 and the part " FTIR and XPS analysis of ligand exchange ") and η_hotIt, can be with to~83% (Figure 30 A) Increase fermi level (Figure 27) (may be due to sulfur doping annealing during) of the NC relative to valence band minimum (VBM).This can To realize the hot carrier extracted and there is the excess energy higher than band edge (up to 0.5 ± 0.1eV), T_cIt is cooled to from~1300 400K (Figure 30 B).

Pass through the relevant η of pump energy_hotIt can reveal that the further evidence of thermoelectron injection Bphen.As shown in figure 23f, with Hot carrier excess energy be reduced to 0.1eV from~0.7eV and (swashed from 3.1eV to 2.5eV using pump energy more than band edge Hair), η_hot15% is reduced to from~72%.These results can verify only that the hot carrier with enough excess energies can be with It injects Bphen (consistent with the energy diagram in Fig. 4 a).They, which are also demonstrated, extracts thermionic Gao Xuan using Bphen and narrow LUMO Selecting property.Importantly, when the thickness of NC film increases to from~35nm~140nm when (Figure 31), after the excitation of 3.1eV light, η_hotFrom ~72% drops sharply to 20% (Figure 23 G).It may be since the limited thermoelectron in NC film expands that the thermoelectron of reduction, which extracts, Caused by scattered/hop range.Figure 31 shows the processing of 1,2- dithioglycol with different thickness according to various embodiments Cross sectional Scanning Electron microscope (SEM) image of nanocrystal (EDT-NC film).Scale bar in Figure 31 (a)-(d) is 100nm。

In contrast, since initial quick hot carrier is cooling, under similar photo-excitation conditions, with a thickness of~ Body block film/Bphen η of 240nm_hotFor~16%, T_cOnly 380K (Figure 30 C-D) is changed to from~450.Even if working as body block film Thickness is reduced to~40nm when, η_hotStill more much smaller than EDT-NC film.

In short, under similar photo-excitation conditions, compared with perovskite body block film, colloid MAPbBr₃NC can be shown slowly The hot carrier cooling time of about 2 orders of magnitude and about 4 times of high hot carrier temperature.Under low pump power density, in NC Hot carrier cooling may be mediated by phonon bottleneck effect, this is unexpectedly relatively slow (with traditional NC phase in lesser NC Than).Conventional understanding in this discovery and traditional colloidal semiconductor nanocrystal is on the contrary, i.e. with the reduction of dimension, with interior Russia Effect of having a rest is more significant, to break through phonon bottleneck.Under high pump power densities, Auger heats the cooling speed of leading hot carrier Rate, may relatively slowly (not observing in conventional NC in the past) in biggish NC.Importantly, these colloid perovskites are nanocrystalline The hot carrier at a slow speed of enhancing in body is cooling to may be implemented effective hot carrier extraction.The result shows that have up to~ The thermoelectron of 0.6eV excess energy can be from surface treated MAPbBr₃NCs film, which is effectively injected, (up to~83%) to be arrived Electron extraction layer, injection length are~0.2ps.

Hot carrier property in perovskite NC can mention for very thin absorber (ETA) and optically focused hot carrier solar battery For new chance.For the former, ETA- solar battery conceptually may be close to the hetero-junctions of dye sensitization.Molecular dye can To be replaced with the semiconductor absorption layer of very thin (~tens nanometer).By nanostructure polarizing electrode (for example, using highly porous TiO₂Bracket, ZnO nanowire array etc.), since surface increases and Multiple Scattering, the effective area covered by thin absorber can be with Increase several orders of magnitude.Most importantly, due to which the path-length of hot carrier is shorter, ETA layers propose hot carrier It may be very useful for taking.For the latter, the lighting power in concentrating solar battery can increase to 1000suns, than 1-sun intensity in representative cells is much bigger, and slower hot carrier is cooling in the perovskite NC of Auger heating induction and can Application.

Various sizes of perovskite nanocrystal synthesis

Zhang et al. reports reprecipitation (LARP) method synthesizing methyl amine lead bromide assisted by ligand (MAPbBr₃) nanocrystal (NC) is (see " bright to shine and the colloid CH of Color tunable₃NH₃PBX₃(X=Br, I, Cl) quantum Point: the potential substitute of display technology ", ACS Nano 9,4533-4542,2015).It, will first in vial 0.16mmol methyl bromide ammonium (MABr), 0.2mmol lead bromide (PbBr₂) mixed in 5mL dimethylformamide (DMF) solution It closes, 50 μ L oleyl amines (OAm) and 0.5mL oleic acid (OAc) is mixed in DMF solution then, form final precursor solution.It will Another round-bottomed flask containing 5mL toluene is preheated to 60 DEG C in oil bath, then under intense agitation prepares 250 μ L Precursor solution inject in hot toluene solution rapidly, solution immediately becomes green, confirms MAPbBr₃The formation of NC.Continue anti- It answers 5 minutes and cooling stops in a water bath.Reaction solution is transferred in centrifuge tube, spherical MAPbBr in different sizes₃NC Required speed centrifugation.By MAPbBr₃NC precipitating is re-dissolved in toluene solution for further studying.For small size, in Size and large scale NC use the centrifugal speed sediment separate out of 12000rpm, 8000rpm and 4000rpm respectively.For small ruler Very little, middle size and large scale NC, average diameter are respectively~4.9,8.9 and 11.6nm (Fig. 6).

MAPbBr ₃Body block filmPreparation

Spin coating contains 0.6M MAPbBr on a quartz substrate₃DMF solution (5000rpm, 12 seconds).In spin coating process, A few drop toluene are added into film after rotation starts 3 seconds.Then film is dried at room temperature for 30 minutes and anneals 5 at 70 DEG C Minute.All film depositions and annealing are all being full of N₂Glove box in complete.The crystallite dimension of body block film is greater than~1 μm, Thickness is about 240nm (Fig. 7).

MAPbBr₃The MAPbBr of NC and EDT processing₃The preparation of NC film

MAPbBr is grown by layer-by-layer spin-coat process method₃The NC of NC film and 1,2- dithioglycol (EDT) processing.All rotations It applies step and is set in 1000rpm, rotational time is fixed as 30 seconds.It, will be in toluene (10mg ml in order to prepare NC film^-1) in Two layers on the glass substrate of NC spin coating.For the NC film of EDT processing, the growth of the NC film of every layer of EDT processing includes three steps: (1) in substrate top spin coating NC solution；(2) NC film is covered with the 2- propanol solution of 0.2M EDT, spin coating again after waiting 30 seconds； (3) dry toluene is added dropwise on film, is then spin coated onto clean remaining long-chain Ligand.It repeats the above process 2-10 times, obtains not The NC film of stack pile.For the sample after annealing, annealing carries out 5 minutes at 70 DEG C.All processing are being full of N₂Gloves It is carried out in case.

Bphen film preparation

By thermal evaporation method 10^-6Under the pressure of support deposit 4,7- diphenyl -1,10- phenanthroline (bathophenanthroline or Bphen).Bphen is with 0.1-0.2nm s^-1Rate be deposited on the perovskite NC film of spin-coated, non-annealing or annealing.

CdSe nanocrystal

The CdSe nanocrystal in toluene is dispersed in purchased from Sigma-Aldrich company.

TA measurement

Transient state suction is carried out in the time range of fs-ns using Helios spectrometer (Ultrafast Systems company) Receive (TA) measurement.Pumping pulse is by optical parametric amplifier (Coherent OPerA Solo^TMOr Light Conversion TOPAS-C^TM) generate, (i.e. Coherent Libra is pumped by 1-kHz regenerative amplifier^TM(50fs, 1KHz, 800nm) or Coherent Legend^TM(150fs, 1KHz, 800nm)), or the basic regenerative amplifier of the 800nm by the way that bbo crystal will be had Frequency multiplication is exported, to obtain 400nm pulse.Two kinds of systems use mode locking titanium sapphire oscillator (Coherent Vitesse^TM, 80MHz).By by the basic 800nm focusing laser pulses of sub-fraction (~10 μ J) regenerative amplifier to 2mm sapphire crystal In (visible-range) or 1cm sapphire crystal (near infrared range), white light continuous probe light beam is generated (in 400nm-1500nm In range).It is received using the cmos sensor for the region UV-VIS and the InGaAs diode array sensor for NIR region Collection detection light beam.During measurement, sample is maintained at room temperature full of N₂Room in.Hot carrier is extracted and is measured, For Bphen/ perovskite/glass substrate sample structure, pump beam excites sample from the side Bphen.

PL and time resolution PL measurement

Stable state PL spectrum is collected with conventional backscattering geometry, and by being coupled to monochromator (Acton, Spectra Pro^TM) charge coupled array (Princeton Instruments, Pixis^TM) detection.The time-evolution of PL by Optronis Optoscope^TMStreak camera system solves.Excitaton source is regenerative amplifier same as described above (Coherent Libra^TM) and optical parametric amplifier (Coherent OPerA Solo^TM).All above-mentioned measurements are in room temperature Lower progress.

TEM, AFM and SEM measurement

The shapes and sizes of NC are measured by transmission electron microscope (TEM, JEOL JEM-2010).It is aobvious by atomic force Micro mirror (AFM, Asylum Research MFP-3D) records the configuration of surface of perovskite NC film, and wherein silicon cantilever is in tapping power mould It is operated under formula.The form and thickness of sample are characterized by scanning electron microscope (SEM, JEOL JSM-7600F).

UPS and XPS measuring

Ultraviolet photoelectron spectroscopy (UPS) is used to study the interface energy level alignment that valence band occupies state.Using identical with XPS Instrument carries out spectral collection.Excitation light source is He-I (h=21.2eV), and lamp power is 50W.It is logical with 2.00eV using CAE mode It crosses energy and acquires photoelectron under surface normal, sample is biased to -10V.Sample is analyzed using x-ray photoelectron spectroscopy (XPS) Composition.Sample is transferred to the analysis room ultrahigh vacuum (UHV) from glove box by airtight sample transfer vessel.The room UHV Pressure is maintained at 1 × 10^-9Under support.Using Al K α (h ν=1486.6eV) photon source excitation sample of 200W, while passing through hemisphere Shape electron energy analyzer (Omicron EA-125) carries out spectral collection.Measurement carries out at room temperature, and photoelectron is along surface method It collects in line direction.

XRD, UV-VIS, AR-FTIR and Raman Measurement

Pass through powder x-ray diffraction (XRD, Bruker D8 Advance) analyzing crystal structure.Using with integrating sphere (ISR-3100) UV-VIS spectrometer (SHIMADZU UV-3600 UV-VIS-NIR spectrophotometer) records absorption spectrum. Pass through the Frontier equipped with general decaying total reflection (ATR) sampling attachment (PerkinElmer, Waltham, MA, USA) The FTIR spectrum of FT-IR/NIR spectrometer (PerkinElmer, Waltham, MA, USA) measurement all samples.It is drawn using WITec Graceful microscope (WITec GmbH, Ulm, Germany) is using 633nm HeNe laser as excitation source record Raman spectrum.

Hot carrier lifetime

It should be noted that the complicated interaction of hot carrier cooling time is caused by following factor:

(i) pump energy (i.e. the excess energy of carrier --- in general, excess energy is higher to lead to hot carrier lifetime more It is long)；

(ii) initial hot carrier density (i.e. usual carrier density is higher to cause hot carrier lifetime longer)；With

(iii) rate of energy loss under particular thermal carrier temperature is (as illustrated in fig 17 a, wherein for from 1600 to 300K Hot carrier temperature, rate of energy loss changes the several orders of magnitude) --- in general, lower hot carrier temperature generate it is lesser Rate of energy loss.(it should be noted that the service life listed is between cooling down the time for reaching 600K from pulse excitation to hot carrier Every.)

In the case where not specified above-mentioned parameter/condition, it is difficult to summarize and partially compare very much different materials Between hot carrier lifetime.In addition, measured hot carrier lifetime may be by the temporal resolution of experimental technique used Limitation, to generate the artificial longer service life, by system time response rather than its intrinsic hot carrier lifetime is limited. For example, passing through time resolution luminescence generated by light using streak camera or Single Photon Counting (TCSPC) system (TRPL) technology measurement hot carrier lifetime may be subjected to the limitation of the systemic resolution of these equipment (i.e. for most of super Streak camera~10ps is usually~50ps for TCSPC system for Hamamatsu system~1ps).Another party PL technology is converted on face, TA or fluorescence to be had < response of the higher system time of 150fs, it can recognize that the more true heat of material carries Flow the sub- service life.Therefore, it is necessary to suitably pay attention to carrying out the value reported in document fair comparison.

Relatively in order to ensure hot carrier temperature and cooling dynamic (dynamical) justice, considering above-mentioned parameter, (i.e. carrier is close Degree, carrier temperature, pump energy and technology) in the case where complete material and summarize, be shown in FIG. 14.In addition, should infuse It is the cooling time interval for reaching 600K from pulse excitation to hot carrier that the hot carrier into Figure 14 of the anticipating cooling service life, which defines, (above-mentioned (iii)).On the basis of the temperature, because previous theoretical calculation is it has been shown that for T_c> 600K, in wide scope It there will still likely be apparent hot carrier transfer efficiency (i.e. > 40%) in absorber band gap.As hot carrier is distributed close to crystalline substance The thermal balance (300K) of lattice, rate of energy loss may become (referring to Figure 17 (a)) much slower.Although these pseudo- " hot carriers " produce It has given birth to the long-life, but they are actually to the operation of hot carrier solar battery almost without contribution.Therefore, ratio is not made herein Compared with.

LO phonon model

Each carrier J_rRate of energy loss by -1.5k_b dT_cThe T that/dt is extracted_cIt determines.J_rIt can be fitted with lower die Type:

Wherein τ_LOIt is feature LO phonon damping time, T_aIt is acoustical phonon temperature,It is phonon energy (~42meV), N_LO (T) it is LO- phonon population under temperature T.The fitting of Fig. 2 a produces and MAPbBr₃NC (~310K) and body block film (~ 305K) comparable T_a.For small, neutralization big NC, τ_LORespectively~340fs, 220fs and 180fs, in contrast, body block film Quick τ_LOAbout 150fs.

Auger heating model

It is relied on from the pump power density of band end light bleaching kinetics and extracts MAPbBr in (Figure 16 (f))₃The Auger of NC declines Become the service life, shows to NC volume (V_NC) sublinear rely on, be τ_Aug~√ (V_NC) (Figure 20 (a)).This behavior with most Closely in weak limitation CsPbBr₃The observed result of biexction auger recombination in NC is consistent, but with τ in strong limitation system_AugTo NC ruler Very little linear dependence is contrasted.Therefore, sublinear dependence is attributable to limitation weaker in our perovskite NC.

It is a three particle processes in view of auger recombination, therefore the Auger rate of heat addition in NC and~n³It is directly proportional, wherein n It is band edge Effective Carrier Density.Therefore, the evolution of hot carrier group can be described with following equation:

Wherein first item represents the relaxation that unrelated hot carrier is heated with Auger, and Section 2 corresponds to Auger heating contribution；C refers to Be band edge carrier auger recombination coefficient.In the lifetime of hot carrier, it is compound to ignore single exciton, because it Service life it is very long (a few nanoseconds).Band edge carrier passes through by n (t)~e^-t/τAugThe main Auger process provided is compound, as One approximation.The direct integral of this equation produces following time-evolution:

Wherein n_hot0It is the initial population of the hot carrier generated, D is equal to c/ (A-3/ τ_Aug).Therefore, the pre- calorimetric current-carrying of equation (4) Subgroup is exponentially decayed, and one of service life corresponds to τ_Aug/3。

In view of the Fermi Dirac distribution of hot carrier, it is close that the effective hot carrier of following relationship calculating can be used Degree:

Figure 20 (c) shows the hot carrier density that calculating is normalized under different pump power densities to die-away time Curve graph.

The estimation of hot carrier diffusion length

MAPbBr₃In hot carrier diffusion length can be estimated as follows.Firstly, the diffusion system of carrier Number depends on preparing the defect concentration of material.The electron diffusion coefficient D of polycrystalline perovskite thin film can be at room temperature (~300K) It is~1cm²s^-1, body block film MAPbBr₃It is 5-8cm²s^-1.Secondly, D can also depend on carrier temperature (T_c), relational expression D=μ κ_BT_c/e.For NC film, using 800K as evenly heat carrier temperature, lower D value is 1cm²s^-1, and in low pump power Hot carrier lifetime is 1ps under density, and hot carrier diffusion length can pass through L=√ (D_hotτ_hot) ≈ 16nm acquisition.~ The diffusion length L ≈ 90nm that high pump power densities under the hot carrier lifetime of 32ps generate.In view of being excited in the side Bphen Perovskite/Bphen sample, and the initial exponential Carrier Profile after fs laser pulse excites in semiconductor, therefore most Hot carrier close to higher concentration in the perovskite of Bphen can more easily inject Bphen.For NC film, it is contemplated that one A little Bphen molecules can penetrate into the upper layer of NC film, and hot carrier undergoes fast hop, therefore, the NC film of~35nm thickness Extracted under low pump power density~70% hot carrier transfer efficiency may be reasonable.For body block film, with 400K As evenly heat carrier temperature, higher D value is 5cm²s^-1, and hot carrier lifetime is under low pump power density 0.15ps, hot carrier diffusion length can be ≈ 10nm.Therefore, it is also reasonable that the transfer efficiency of body block film, which is~15%,.

The FTIR and XPS analysis of ligand exchange

The MAPbBr of EDT processing₃The FTIR spectrum of NP, which is shown, efficiently removes original oleic acid and oleyl amine ligand (Figure 24).From 2921 and 2841cm^-1The CH at place₂The reduction of stretching can be clearly observed the removal of these ligands.In 1710cm^-1The C=O at place Stretching completely removes, and in 800cm^-1Locate the rocking vibration of N-H and in 1384cm^-1The disappearance of the C-O-H key at place, further Support the EDT ligand exchange of oleic acid and oleyl amine ligand.

The MAPbBr of the EDT of non-annealing and after annealing processing₃It is bimodal that the XPS analysis of sulphur in NC discloses two groups of S 2p, Wherein 2p^3/2Peak be located at combination can be for~162.5eV and~164.2eV (after annealing~162.7eV and~164.3eV) at, difference It is generated by the combination mercaptides and unbonded mercaptan of EDT to the surface NC (Figure 24).Combined in NC without after annealing-unbonded The ratio of thiol group is~1.04, increases to~1.47 in the NC of after annealing at 70 DEG C.Therefore, after annealing processing is further Increase the electronics coupled of EDT-NC and Bphen.

Influence of the Trions to hot carrier in photoelectricity NC and NC film

Figure 16 (e) shows middle sized nanocrystals (NC) the band end light bleaching kinetics ratio with spin-coating film in solution Compared with.From exponential fitting (solid-line curve), the service life changes to~3ns from~4.5 under low pump power density, acceleration may be by In the presence of optical charge NC.Under high pump power densities, other than auger recombination, may occur in the NC film of spin coating fast Fast Decay~290ps, this is attributable to Trions (photoelectricity exciton).However, they only cause the lower energy side of GSB Broaden (the bleaching magnetic tape trailer of the lower energy side of the NC film in 6 referring to fig. 2, in the solution in the pseudo-colours TA spectrum in Figure 10 NC compare).The energy reduction of Trions may be due to exciton-exciton interaction.Trions in NC film may not Influence the dynamics for being located at the hot carrier of GSB higher energy side.

Control experiment is to verify hot carrier transfer

MAPbBr₃NC film shows the cooling dynamics of similar hot carrier in the case where handling with/without EDT.Do not having In the case where having EDT processing, NC shows and has the/cooling dynamics of the similar hot carrier without Bphen extract layer.This Outside, it has been found that undergone in hot vaporizer in the NC film of identical processing, in addition to being practically without Bphen layers of deposition, heat Carrier properties do not have any significant change.

The PIA signal of the electric charge carrier shifted in Bphen

For original Bphen film, (with reference to the absorption spectrum in Figure 28 (a)) when being excited more than the band gap of 300nm light, There are very wide photoinduction hydrophilicity (PIA, Figure 28 (b)), typical organic semiconductors (such as P3HT, PCBM) within the scope of NIR.Its Intensity is gradually increased with the increase of probe wavelength.PIA band can temporarily be generally directed to the suction of Photogenerated Radicals anion in Bphen It receives.The excitation of control experiment Bphen 400nm (be lower than band gap) (under low pump power density and high pump power densities) Invalid (PIA) feature (Figure 28 (b)) is generated, shows that there is no Photogenerated Radicals anions in Bphen.

For EDT-NC/Bphen sample (NC film thickness~50nm), NC is selectively excited with 400nm light.In low pumping It, may be without measurable TA signal under power density.This may be due to TA signal (radical anion generated indirectly) Lower than the detection limit (10 of TA setting^-4ΔT/T).(i.e.~15 μ J cm under higher pump power density^-2, correspond to<N>~ 2.5) the weak PIA band (Figure 28 (b) and (c)) similar to original Bphen, can be observed.However, pump power is any into one Step increases the degradation that all may cause perovskite.

Control experiment is also displayed without from 500nm excitation, (i.e. photoexcitation carrier in NC has insignificant mistake Surplus energy) under EDT-NC/Bphen sample and the individual TA of NC film in the case where 400nm high pump power densities excite (Figure 28 (b)) Signal.Therefore, these experiments show that the PIA that observes in EDT-NC/Bphen hybrid may be only by hot carrier from NC Injection Bphen causes.

In addition, the relaxation of PIA can have a rapid decay service life (original Bphen be~70ps, NC/Bphen be~ 25ps) and slow-decay service life (original Bphen is~1ns, and NC/Bphen is~0.5ns) (Figure 28 (d)).Rapid decay May be in the defect due to carrier capture to original Bphen and additional electron inversion to NC/Bphen NC.Slowly Decaying may be due to the hole-recombination in the NC in the radical anion/exciton and NC/Bphen hybrid in Bphen.Most Afterwards, it is contemplated that the energy difference in NC between thermoelectron and hot hole (is~3.1eV) and Bphen band under most of extreme cases Gap (3.5eV) is compared to smaller, pole a possibility that by generating carrier in Bphen from the compound energy transmission of hot carrier It is small.

Estimate antielectron transfer time

Back transfer of the injected electrons from Bphen to NC can cause the relaxation time of electronics in the NC in TA signal Increase.The antielectron rate of transform (1/ τ_bk) EDT-NC film (1/ τ can be passed through_NC) and EDT-NC/Bphen duplicature (1/ τ_NC/Bp) it Between the variable quantity of band edge bleaching relaxation rate of NC estimate, i.e. 1/ τ_bk=1/ τ_NC-1/τ_NC/Bp)。

In low pump power density (< N₀>~0.1) under, the relaxation power of EDT-NC film and EDT-NC/Bphen duplicature Invariance (Figure 29 (a)) is proved there are very small antielectron transmission rate and more than the long pass of our time of measuring windows The defeated time, this may be since fast Acquisition and positioning hinder carrier drift and return to NC film.Therefore, long τ_bkBe conducive to thermoelectricity Son injection.In high pump power densities (< N₀>~2.5) under, τ_NC/ Bp is obviously prolonged (Figure 29).Use above-mentioned relation formula, estimation Antielectron time τ_bkFor~80ps.The antielectron transfer time (i.e. increased antielectron transfer rate) of reduction and reduced heat Electron injection efficiency is consistent, from < N₀The 72% of>~0.1 is reduced to<N₀The 58% of >~2.5.

Although the present invention is specifically illustrated and described by reference to specific embodiment, those skilled in the art should be managed Solution, without departing from the spirit and scope of the present invention, can carry out various changes in form and details.Therefore, originally The range of invention is indicated by appended claims, and is covered all in the meaning and scope for falling into the equivalent of claim Change.

Claims

1. a kind of hot carrier solar battery, comprising:

Nanocrystal layer comprising one or more nanocrystals, each in one or more nanocrystals include Halide perovskite material；

First electrode, the first side contacts with the nanocrystal layer；With

Second electrode, the second side contacts with the nanocrystal layer, described second side are opposite with first side；

Wherein the thickness of the nanocrystal layer is less than 100nm.

2. hot carrier solar battery according to claim 1, further includes: a kind of Optical devices, the Optical devices By solar energy to guide to the nanocrystal layer.

3. hot carrier solar battery according to claim 2, wherein the Optical devices include one or more light Element is learned, the optical element is by solar energy to guide to the nanocrystal layer.

4. hot carrier solar battery according to claim 3, wherein one or more of optical elements are optics Lens.

5. hot carrier solar battery according to any one of claim 1 to 4, wherein the first electrode is thermoelectricity Sub- extract layer, including any one in following material: titanium oxide, zinc oxide, phenyl-C61- methyl butyrate, 4,7- bis- Phenyl -1,10- phenanthroline, poly- (9- vinyl carbazole), 2- (4- xenyl) -5- phenyl -1,3,4- oxadiazoles, 2,2', 2 " - (1,3,5- benzene pawl base)-three (1- phenyl -1-H- benzimidazole), poly- (9,9- dioctyl fluorene) and bathocuproine.

6. hot carrier solar battery according to any one of claim 1 to 5, wherein the second electrode is hot empty Cave extract layer, including any one in following material: 2,2', 7,7'- tetra- [N, N- bis- (4- methoxyphenyl) amino]- Two fluorenes of 9,9'- spiral shell, poly- (3- hexyl thiophene -2,5- pitch base), poly- (3,4- Ethylenedioxy Thiophene) poly styrene sulfonate and poly- (9,9- dioctyl-fluorenes-co-N- (4- butyl phenyl) diphenylamines.

7. hot carrier solar battery according to any one of claim 1 to 6, wherein the first electrode is energy Selective exposure point allows the electronics with the excess energy equal to or higher than predetermined value to pass through, and will have lower than pre- The electron back of the excess energy of definite value is emitted back towards the nanocrystal layer.

8. hot carrier solar battery according to any one of claim 1 to 7, wherein the second electrode is energy Selective exposure point allows the hole with the excess energy equal to or higher than predetermined value to pass through, and will have lower than pre- The hole reflections of the excess energy of definite value return the nanocrystal layer.

9. hot carrier solar battery according to any one of claim 1 to 8, wherein one or more nanometers Crystal shows the cooling service life of the hot carrier higher than 30ps.

10. hot carrier solar battery according to any one of claim 1 to 9, one or more received wherein described The radius of each in meter Jing Ti is the arbitrary value selected from 2nm to 7nm.

11. hot carrier solar battery according to any one of claim 1 to 10, wherein the halide perovskite Material is organic and inorganic halide perovskite material.

12. hot carrier solar battery according to any one of claim 1 to 10, wherein the halide perovskite Material is inorganic halides perovskite material.

13. a kind of forming method of hot carrier solar battery, comprising:

The nanocrystal layer including one or more nanocrystals is provided, each packet in one or more nanocrystals Include halide perovskite material；

First electrode is formed, so that the first side contacts of the first electrode and the nanocrystal layer；With

The second electrode lay is formed, so that the second side contacts of the second electrode and the nanocrystal layer, wherein described second Side is opposite with first side；

Wherein the thickness of the nanocrystal layer is less than 100nm.

14. according to the method for claim 13, further includes: form Optical devices, the Optical devices are by solar energy to guide To the nanocrystal layer.

15. according to the method for claim 14, wherein the Optical devices include one or more optical elements, the light Element is learned by solar energy to guide to the nanocrystal layer.

16. according to the method for claim 15, wherein one or more of optical elements are optical lenses.

17. method described in any one of 3 to 16 according to claim 1, wherein the first electrode is thermoelectron extract layer, packet Include any one in following material: titanium oxide, zinc oxide, phenyl-C61- methyl butyrate, 4,7- diphenyl -1,10- are luxuriant and rich with fragrance Cough up quinoline, poly- (9- vinyl carbazole), 2- (4- xenyl) -5- phenyl -1,3,4- oxadiazoles, 2,2', 2 "-(1,3,5- benzene pawls Base)-three (1- phenyl -1-H- benzimidazoles), poly- (9,9- dioctyl fluorene) and bathocuproine.

18. method described in any one of 3 to 17 according to claim 1, wherein the second electrode is hot hole extract layer, packet Include any one in following material: 2,2', 7,7'- tetra- [N, N- bis- (4- methoxyphenyl) amino] -9,9'- spiral shell two Fluorenes, poly- (3- hexyl thiophene -2,5- pitch base), poly- (3,4- Ethylenedioxy Thiophene) poly styrene sulfonate and poly- (9,9- bis- is pungent Base-fluorenes-co-N- (4- butyl phenyl) diphenylamines.

19. method described in any one of 3 to 18 according to claim 1, wherein the second electrode is energy selectivity contact Point allows the hole with the excess energy equal to or higher than predetermined value to pass through, and will have the surplus for being lower than predetermined value The hole reflections of energy return the nanocrystal layer.

20. method described in any one of 3 to 19 according to claim 1, wherein the first electrode is energy selectivity contact Point allows the electronics with the excess energy equal to or higher than predetermined value to pass through, and will have the surplus for being lower than predetermined value The electron back of energy is emitted back towards the nanocrystal layer.

21. method described in any one of 3 to 20 according to claim 1, wherein one or more nanocrystals are shown The hot carrier cooling service life higher than 30ps.

22. method described in any one of 3 to 21 according to claim 1, wherein every in one or more nanocrystals A kind of radius is the arbitrary value selected from 2nm to 7nm.

23. method described in any one of 3 to 22 according to claim 1, wherein the halide perovskite material is organic-nothing Machine halide perovskite material.

24. hot carrier solar battery described in any one of 3 to 22 according to claim 1, wherein the halide calcium titanium Pit wood material is inorganic halides perovskite material.