CN110896129A

CN110896129A - Multi-exciton dissociation heterojunction based on perovskite nanocrystalline and acene molecular material

Info

Publication number: CN110896129A
Application number: CN201811067379.2A
Authority: CN
Inventors: 吴凯丰; 罗消
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2018-09-13
Filing date: 2018-09-13
Publication date: 2020-03-20

Abstract

The invention relates to a multi-exciton dissociation heterojunction based on a perovskite nanocrystal-acene organic molecule hybrid material. The heterojunction uses perovskite nanocrystalline as light absorption layer material, and acene molecule as multi-exciton dissociation layer material. The large extinction coefficient of the perovskite nanocrystal is utilized to absorb light efficiently, and the acene molecules quickly extract holes in the perovskite to realize exciton dissociation. The perovskite nanocrystal size is 1-50 nanometers, and can be all-inorganic perovskite or organic-inorganic hybrid perovskite. By time-resolved spectroscopic detection techniques, we observed CsPbBr_2.625Cl_0.375The hole transfer time to TCA molecules is 7.6 picoseconds, and the lifetime of the charge separation state is longFor 5.1 microseconds. The ultra-long charge separation state facilitates the heterojunction to dissociate 6 photogenerated excitons.

Description

Multi-exciton dissociation heterojunction based on perovskite nanocrystalline and acene molecular material

Technical Field

The invention relates to a multi-exciton dissociation heterojunction based on a perovskite nanocrystal-acene organic molecule hybrid material.

Background

In photoelectron application, the trihalo perovskite nano-crystal is a photoelectric material with great potential. The material has excellent light absorption and emission performance, so that the material can be used for preparing photoelectric devices such as high-performance solar cells, photodetectors, light emitting diodes and the like. The functionalization of perovskite nanocrystals with organic molecules is an effective strategy for achieving novel optoelectronic properties. The strategy mainly utilizes basic kinetic processes such as charge or energy transfer between perovskite nanocrystals and molecules. For example, nanocrystal-to-molecule charge transfer can be used in solar energy conversion to drive photochemical reactions; on the other hand, energy transfer can transfer light energy absorbed by the nanocrystal to molecules to realize photoluminescence or multi-exciton generation.

In semiconductors, hole transfer is generally slower than electron transfer, which increases charge recombination losses in the photoelectric conversion system, thereby limiting the efficiency of many energy conversion processes. The acene molecules are high-efficiency hole transport materials, and can be used for constructing a heterojunction with other semiconductor materials to extract holes in the semiconductor materials. Meanwhile, the nanocrystal and the acene molecule have stronger electron coupling effect, so that picosecond-level ultrafast hole transfer can be realized from the nanocrystal to the acene molecule. Typically, the double-exciton auger recombination time is in the range of tens of picoseconds, and acene molecules can be used to dissociate multiple excitons in perovskite nanocrystals.

The method comprises the following steps of designing and synthesizing all-inorganic perovskite nanocrystals, constructing a heterojunction with energy level-matched tetracene molecules, and detecting that the photon luminescence intensity of the nanocrystals is quenched by 300 times through time-resolved fluorescence spectroscopy; meanwhile, the femtosecond transient absorption spectrum is used for detecting that the hole transfer time constant from the nanocrystal to the tetracene molecule is 7.6 picoseconds, and the service life of the charge separation state is 5.2 microseconds. Further, excitation power saturation experiments show that tetracene molecules can dissociate up to 6 photogenerated excitons through a multi-hole transfer process, so that Auger recombination in the perovskite nanocrystal is remarkably inhibited, and an obvious multi-exciton dissociation process is shown. The invention provides a foundation for future development of high-performance photoelectronic devices based on perovskite and lays a precondition for the final realization of commercialization.

Disclosure of Invention

The invention aims to provide a multi-exciton dissociation heterojunction based on a perovskite nanocrystal-acene organic molecule hybrid material so as to solve the technical problem of difficult multi-exciton dissociation in the optoelectronic device.

The multi-exciton dissociation heterojunction uses perovskite nanocrystalline as a light absorption layer material, and acene molecules as a multi-exciton dissociation layer material.

The perovskite nanocrystal can be all-inorganic perovskite (CsPbX)₃X ═ Cl, Br and I, or one or more kinds thereof), and may be an organic-inorganic hybrid perovskite (MAPbX)₃And FAPBX₃，MA＝CH₃NH₃，FA＝CH(NH₂)₂X ═ Cl, Br, and I) may be used.

The multi-exciton dissociation heterojunction is prepared by adopting a method known in the field. The preferred perovskite nanocrystal is CsPbBr_2.625Cl_0.375(hereinafter referred to as NC); preferred acene molecules are carboxyl-modified tetracenes having carbon atom number 5 (hereinafter abbreviated as TCA); the optimal preparation method is ultrasonic self-assembly, the scheme is simple to prepare, and optoelectronic devices with low processing cost are expected to be realized in the future.

In order to verify whether the synthesized perovskite nanocrystal-acene heterojunction really realizes an efficient multi-exciton dissociation process, the invention adopts a verification technical scheme as follows:

and determining that the TCA molecules are self-assembled on the surface of the perovskite nanocrystalline by an ultrasonic method by using the steady-state absorption spectrum.

By combining steady-state fluorescence with a time-resolved fluorescence spectroscopy technology, the photoluminescence intensity of the perovskite nanocrystal is obviously quenched, and the fluorescence lifetime is obviously shortened.

And determining a hole transfer time constant, a charge separation state time constant, a double-exciton Auger life and a multi-exciton dissociation spectrum from the perovskite nanocrystal to TCA molecules by utilizing a femtosecond transient absorption spectrum technology, and further calculating and determining the dissociation number of the multi-exciton.

Drawings

FIG. 1, (a) UV-visible absorption spectra of NC, TCA and NC-TCA; (b) steady state fluorescence spectra of NC and NC-TCA, where the inset is a time resolved fluorescence spectrum.

FIG. 2, transient absorption spectra (a) and (c) and excited state kinetics (b) and (d) of NC and NC-TCA.

FIG. 3, transient spectral dynamics (a) and (c) of NC and NC-TCA at different excitation powers; dual exciton recombination kinetics in NC (b); transient spectral dynamics of NC-TCA at different excitation powers normalized within 20-50 picoseconds (d).

FIG. 4 shows the average number of dissociation excitons < N > of NC-TCA in excited state as a function of the average number of excitons < N >.

Detailed Description

The invention is further illustrated by means of examples and figures.

Examples

The preparation method of the multi-exciton dissociation heterojunction based on the perovskite nanocrystal-acene organic molecule hybrid material comprises the following steps:

a0.1. mu. mol NC (size 10nm) hexane solution (2mL) was mixed with 2mg of a TCA molecule and placed in an ultrasonic machine for 10 minutes, followed by filtration through a 0.25 μm pore size polytetrafluoroethylene filter to obtain an NC-TCA solution having a UV-visible steady state absorption spectrum as shown in FIG. 1a (the spectrum was obtained using an Agilent carry 5000 apparatus at a concentration of 0.05mmol/L), and since the TCA molecule is insoluble in the hexane solution, it was confirmed that the TCA molecule is coordinately bound to NC. Meanwhile, 0.1. mu. mol NC (size 10nm) was dissolved in 2mL of a hexane solution as a reference sample.

Whether the prepared NC-TCA heterojunction can realize multi-exciton dissociation or not needs to be verified by an optical detection means, and the verification detection is mainly carried out from the following three aspects:

(1) and (3) carrying out photoluminescence quenching and fluorescence lifetime detection on the NC-TCA system.

By utilizing a steady-state fluorescence and time-resolved fluorescence detection means, photoluminescence of NC in an NC-TCA system is tested (the excitation wavelength is 340nm and is obtained by adopting an Agilent Cary Eclipse fluorescence spectrophotometer), and as shown in figure 1b, the fluorescence of the NC-TCA system is quenched by 300 times under the same concentration (0.05 mmol/L); meanwhile, the fluorescence lifetime of NC-TCA is also obviously reduced through time-resolved fluorescence spectrum detection, and the data result is shown in an inset of FIG. 1 b.

(2) And detecting the hole transfer time and the charge separation state life of the NC-TCA system.

The formation kinetics of the first exciton absorption peak bleaching signal of the NC-TCA System is detected by a femtosecond transient absorption spectrum detection means (femtosecond spectrometer of Ultrafast System, pump light: 350 nm; probe light: 350-.

FIGS. 2a and 2b are respectively the transient absorption spectrum and its dynamic curve and fitting corresponding to NC; FIGS. 2c and 2d are the corresponding transient absorption spectrum of NC-TCA and its kinetic curve and fit, respectively. It can be seen that NC has a longer exciton state lifetime, which is-5 nanoseconds by kinetic fitting; in contrast, the NC-TCA system showed rapid decay of the ground state bleaching signal within 20 picoseconds (fig. 2c and 2d), corresponding to an ultrafast hole transfer process from NC to TCA, while the system had slow decay of the signal within a time scale of 60 picoseconds to 60 microseconds, corresponding to a long-lived charge-separated state with a lifetime of-5 microseconds, as shown by kinetic fitting.

(3) Multiple exciton dissociation of the NC-TCA system.

By performing excitation power saturation experiments on the NC-TCA system (fig. 3a and 3b), the dual exciton lifetime of NC can be determined to be 73 picoseconds (fig. 3b), and the average number of excitons at the corresponding power < N > (fig. 3a inset). Simultaneously, excitation power saturation experiments were also performed on NC-TCA samples at each of the corresponding powers (fig. 3c and 3 d). The functional relation between < N > and the average dissociation exciton number < N > can be obtained through calculation (figure 4), and the NC-TCA system can be determined to be capable of dissociating up to 6 photogenerated excitons, so that the auger recombination loss of the system is effectively overcome (the calculation method is detailed in the references Ann.Rev.Cond.Matt.Phy.2014,5, 285-.

The perovskite nanocrystal is CsPbBr_2.625Cl_0.375Optimized energy level matching is realized with tetracene molecules (TCA) modified by carboxyl of the number 5 carbon atom. By time-resolved spectroscopic detection techniques, we observed CsPbBr_2.625Cl_0.375The hole transfer time to the TCA molecule was 7.6 picoseconds and the charge separation lifetime was as long as 5.1 microseconds. The ultra-long charge separation state promotesThe heterojunction can dissociate 6 photogenerated excitons.

In conclusion, the multi-exciton dissociation heterojunction based on the perovskite nanocrystal-acene organic molecule hybrid material can really realize ultra-fast hole transfer and ultra-long charge separation state, and finally realize the purpose of multi-exciton dissociation. The method has great guiding value and significance for the research and development of high-performance devices based on perovskite nanocrystals in the future.

Claims

1. A multi-exciton dissociation heterojunction based on perovskite nanocrystalline and acene molecule material is characterized in that: the heterojunction uses perovskite nanocrystalline as light absorption layer material, semiconductor particles with the size of 1-50 nanometers (preferably 10 nanometers), acene molecules as a multi-exciton dissociation layer and are combined on the surface of the nanocrystalline through chemical coordination bonds; the molar ratio of the acene molecules to the perovskite nanocrystals is controlled to be 1-300 (preferably 180).

2. A heterojunction as claimed in claim 1, wherein: the perovskite nano crystal can be one or more than two of all-inorganic perovskite or organic-inorganic hybrid perovskite;

the all-inorganic perovskite is CsPbX₃X is one or more of Cl, Br or I;

the organic-inorganic hybrid perovskite is MAPbX₃Or FAPBX₃，MA＝CH₃NH₃，FA＝CH(NH₂)₂And X is one or more of Cl, Br and I.

3. A heterojunction as claimed in claim 1, wherein: the acene molecule is one or more than two of naphthalene, anthracene, tetracene, pentacene, hexacene and derivatives thereof.

4. A heterojunction as claimed in claim 1, wherein:

the perovskite nanocrystal is CsPbBr_2.625Cl_0.375，The acene molecule is modified by carboxyl of carbon atom number 5Tetracene molecules (TCA).