KR20210049659A - High efficiency perovskite solar cell and method for manufacturing same - Google Patents

Abstract

According to a manufacturing method of a perovskite solar cell of the present invention, a surface of an electron transport layer is first modified with an alkali metal halide and an alkali metal and a halide can diffuse into a perovskite crystal to passivate a defect trap by a process of annealing after coating a perovskite precursor solution thereon. Accordingly, the present invention is to provide a high efficiency perovskite solar cell having long-term stability and very little hysteresis by effective doping of the alkali metal and the halide.

Description

High efficiency perovskite solar cell and its manufacturing method {HIGH EFFICIENCY PEROVSKITE SOLAR CELL AND METHOD FOR MANUFACTURING SAME}

The present invention relates to a high-efficiency perovskite solar cell having improved long-term stability and very little hysteresis, and a method of manufacturing the same.

Organic-inorganic hybrid perovskite (OIHP)-based solar cells have recently attracted attention as a low-cost power source due to high power conversion efficiency (PCE) and solution processability (WS Yang et al., Science. 356, 1376-1379). (2017)). In particular, PCE has improved rapidly from 3.8% to 24.2% over the past 10 years through the development of OIHP photoactive material, electron transport layer (ETL) and hole transport layer (HTL) of perovskite solar cell (PSC). As a component of ETL that determines the processing temperature of these PSCs, high-temperature (≥ 450°C) sintered TiO ₂ has been used. Recently, the demand for low-temperature processing ETL for flexible PSCs is continuously increasing, but these have a problem that is inferior to _{that of high-temperature processing TiO 2 in terms of performance (charge extraction characteristics, stability, etc.).}

ZnO is a promising low-temperature ETL candidate for PSC due to its solution processability, high electron mobility, and adequate energy levels. Solution-processed ZnO has been successfully used in organic photovoltaic devices and quantum dot solar cells, but there is a problem in using it in PSCs due to the interfacial reverse decomposition reaction. ZnO induces a proton-transfer reaction at the ZnO/OIHP interface due to its characteristics, causing decomposition of OIHP, thereby lowering the stability of PCE and PSC. Therefore, research to minimize reverse decomposition through surface passivation has been intensively conducted. Nevertheless, the ZnO-based PSC reported so far showed significantly lower performance compared to the _{TiO 2 based PSC.}

Therefore, development of a ZnO-based low-temperature processing PSC with a performance level comparable to that of a _{TiO 2 based PSC is required.}

W. S. Yang et al., Science. 356, 1376-1379 (2017)

In a perovskite solar cell (PSC), the defect trap state at the interface between the organic-inorganic hybrid perovskite (OIHP) active layer and the electron transport layer (ETL) is the power conversion efficiency (PCE), hysteresis, long-term stability, and effective passivation. It is an important factor in determining the performance of the back.

Accordingly, the present inventors noted that alkali metals can effectively suppress ETL/OIHP interface defects and internal trap sites in OIHP crystals, and that passivation of anionic defects can be achieved by doping halide atoms in OIHP crystals. . Based on this, it can be expected that the defect passivation of OIHP crystal and ZnO/OIHP interface can be remarkably improved through simultaneous doping of alkali metal and halide, but isopropanol (IPA), dimethylformamide (DMF) and dimethyl sulfoxide. Since the solubility of the alkali metal halide in the OIHP precursor solution using a polar solvent such as side (DMSO) was poor, it was difficult to actually implement this. However, as a result of continued research by the present inventors, by the process of first modifying the surface of the electron transport layer with an alkali metal halide, coating a perovskite precursor solution thereon, and then annealing, the alkali metal and the halide are converted into a perovskite precursor. It has been found that it can diffuse into the coating layer and passivate the defect trap.

Accordingly, an object of the present invention is to provide a method of manufacturing a high-efficiency perovskite solar cell having long-term stability and very little hysteresis through effective doping of an alkali metal and halide, and a perovskite solar cell thereof.

The present invention comprises the steps of: (1) forming a modified electron transport layer by coating an alkali metal halide solution on the electron transport layer; And (2) coating a perovskite precursor solution on the modified electron transport layer and then annealing the perovskite precursor coating layer to form a perovskite photoactive layer. It provides a method of manufacturing.

In addition, the present invention is a substrate; A first electrode layer; An electron transport layer containing an electron transporter; A photoactive layer containing perovskite; Hole transport layer; And a second electrode layer in a sequentially stacked form, wherein the electron transport layer and the photoactive layer further contain the same alkali metal and halide, providing a perovskite solar cell.

According to the method of manufacturing a perovskite solar cell of the present invention, the surface of the electron transport layer is first modified with an alkali metal halide, and then the surface of the electron transport layer is coated with a perovskite precursor solution, followed by annealing. May diffuse into the perovskite precursor coating layer to passivate the defect trap.

Accordingly, the present invention can provide a high-efficiency perovskite solar cell having long-term stability and very little hysteresis by effective doping of an alkali metal and halide.

The meanings of the abbreviations described in the description and drawings below are as defined in the examples.
1 shows the modification by alkali metal chloride, where A is the element mapping (K and Cl) in the SEM image of the modified ZnO layer, B is the XRD pattern of the modified OIHP layer, and C is the modified with KCl. Cross-sectional TEM image of L-PSC (HAABF image and element mapping from EDS, using FIB cutting), D is XPS depth profiling result of KCl modified sample (Si/ZnO/OIHP) and enlargement of K and Cl profile It is a curve.
2 shows the effect of the modification on the interface and the internal trap site, where A is the PL emission intensity mapping of the KCl modified sample (811 nm wavelength) and the unmodified control sample (817 nm wavelength) on a glass substrate ( 20 μm × 20 μm area), B is the TCSPC analysis result of the glass/OIHP sample, and C is the trap DOS profile of the OIHP sample obtained by DLCP analysis.
As Figure 3 showing the performance of the L-PSC, A is a structure of a planar heterojunction L-PSC, B is a schematic view of a KCl passivation in OIHP crystal, C is a JV characteristics of the modified L-PSC (100 mWcm ^{- 2} illumination, AM 1.5G one sun illumination, reverse scan), and D is the PCE value stabilized at the maximum power point output (0.89V for the unmodified control L-PSC and 0.94V for the L-PSC-KCl). And E and F represent the distributions (30 samples) of V _{OC values and PCE values in L-PSC, respectively.}
4 shows the effect of alkali metal chloride on photocurrent hysteresis, where A and B represent the C _p - V characteristics of unmodified L-PSC (control) and L-PSC-KCl, respectively, under various lighting, and C is OIHP. Represent the temperature-dependent conductivity of the layer, and D and E represent the schematic diagram of the charge trap in the OIHP layer and the interface of the unmodified control L-PSC and the modified L-PSC, respectively.
5 shows the trap status and stability analysis, where A shows the distribution of the trap status of L-PSC by TAS measured at 290 K, and B and C are the unmodified control L-PSC and KCl modified L-, respectively. PSC shows the change in trap state after 2 weeks of storage in air, D, E and F are long-term stability in air (40±5%RH) for unencapsulated L-PSC, 70℃ continuous in glove box (nitrogen filling) Thermal stability under heating (error bars are standard deviation of 5 samples), and light stability by continuous MPP tracking under ^{100 mWcm -2 illumination (one sun LED) in a glove box, respectively.}
6A, B, and C show the JV characteristic, the histogram of the V _OC value and the histogram of the PCE value (15 samples) for a ^{large area (active area 1.12 cm 2} ) L-PSC-KCl, respectively, D, E, F, G and H are JV properties for flexible L-PSC-KCl samples, bending cycle test results (> 1000 cycles, bending radius 6.9 mm), bending radius test results, histogram of V _OC values and histogram of PCE values. (15 samples) are shown respectively.
7 shows the XPS analysis results of the ZnO layer modified with alkali metal chloride, where A is the Cl 2p peak of the modified ZnO layer, B is the Li 1s peak of ZnO-LiCl, C is the Na 1s peak of ZnO-NaCl, D represents the K 2p peak of ZnO-KCl, E represents the Cs 3d peak of ZnO-CsCl, and F, G and H represent the Cl/Zn atomic ratio, alkali metal/Zn atomic ratio and Zn 2p spectrum of the modified ZnO layer. Respectively.
8A to 8F are the results of O 1s core level XPS analysis of the unmodified sample (control) and the modified sample, and G is the PL emission spectrum of the modified ZnO layer.
9 is a result of charge extraction analysis at the ZnO/OIHP interface modified or not modified by alkali metal chloride, where A is a steady state PL emission spectrum, and B is a TCSPC analysis result of a ZnO/OIHP sample.
A, B, C, D and E of FIG. 10 are SEM images of the perovskite layer formed on unmodified ZnO (control), ZnO-LiCl, ZnO-NaCl, ZnO-KCl and ZnO-CsCl, respectively (50,000 magnification). And F, G, H, I and J are the perovskite particle size distributions (2 to 3 samples) formed on unmodified ZnO (control), ZnO-LiCl, ZnO-NaCl, ZnO-KCl and ZnO-CsCl, respectively. )to be.
FIG. 11 shows the FWHM values of the perovskite (110) peak in FIG. 1B (3 to 5 samples, circles and bars represent mean and standard deviation, respectively).
12 shows a cross-sectional TEM image (HAABF and elemental mapping, using FIB cutting) of an unmodified L-PSC.
13 shows a cross-sectional TEM image (HAABF and element mapping, using FIB digestion) of a low concentration (2 mM) KCl-modified L-PSC.
14 is a result of XPS depth profiling of an unmodified sample (Si/ZnO/OIHP), where A is the profile of all measured elements, and B is an enlarged view of K and Cl profiles.
15A is a PL wavelength mapping image of KCl-modified or unmodified OIHP, B is a schematic diagram of the origin of PL blue-shift by modification, and C and D are the unmodified samples (control) and KCl-modified samples, respectively. It is the peak wavelength distribution of the PL emission.
16 is a JV curve of L-PSC-KCl modified under various conditions.
17A, B, C, D and E are EQE spectra of unmodified L-PSC (control), L-PSC-LiCl, L-PSC-NaCl, L-PSC-KCl and L-PSC-CsCl, respectively. .
18A and B show distributions (30 samples) of V _OC and PCE of L-PSC modified with different alkali metal chlorides, respectively.
19 is a charge extraction characteristic analysis result, where A is a photovoltage attenuation curve by TPV, B is a photocurrent attenuation curve by TPC, and C and D are IMVS and IMPS analysis results, respectively.
A, B, C, D and E in Figure 20 are the reverse and forward directions of unmodified L-PSC (control), L-PSC-LiCl, L-PSC-NaCl, L-PSC-KCl and L-PSC-CsCl, respectively. It shows the photocurrent hysteresis under the scan.
21 shows a device configuration for measuring temperature-dependent conductivity.
22 shows a Mott-Schottky curve of L-PSC.
23 shows the trap density by TPV/TPC analysis.
24A and B show photographic images of unmodified OIHP (control) and KCl-modified OIHP layers for annealing (100°C, 55%RH) duration, respectively, and C and D are absorption spectra according to annealing duration. And E and F represent the XRD of the OIHP layer according to the annealing duration time.
25 is a result of JV analysis for unmodified L-PSC having an active area ^{of 1.12 cm 2.}
26 is an EQE spectrum of a large area L-PSC.

Hereinafter, a high-efficiency perovskite solar cell of the present invention and a method of manufacturing the same will be described in detail.

<Method of manufacturing perovskite solar cell>

A method of manufacturing a perovskite solar cell according to the present invention includes the steps of: (1) coating an alkali metal halide solution on an electron transport layer to form a modified electron transport layer; And (2) coating the perovskite precursor solution on the modified electron transport layer and then annealing the perovskite precursor coating layer to form a perovskite photoactive layer.

Hereinafter, each step will be described in more detail.

(1) Modification of the electron transport layer

In the above step (1), a modified electron transport layer is formed by coating an alkali metal halide solution on the electron transport layer.

The electron transport layer may contain a metal oxide. The metal oxide may be, for example, an oxide of at least one metal selected from the group consisting of Zn, Sn, Ti, and Al. Specifically, the metal oxide may be an oxide of at least one metal of Zn and Sn. The metal oxide may or may not be doped with one or more metals, and the doped metal may be one or more selected from the group consisting of Al, Mg, In, Zn, Ga, and Sr. As a specific example, the metal oxide may be magnesium-doped zinc oxide, tin-doped zinc oxide, tin oxide, zinc-doped tin oxide, indium-doped tin oxide, or zinc oxide. More specifically, it is preferable that the electron transport layer contains ZnO because a low-temperature process is possible.

The alkali metal halide solution may contain at least one selected from the group consisting of K, Li, Na and Cl as an alkali metal. In addition, the alkali metal halide solution may contain at least one selected from the group consisting of F, Cl, Br and I as a halide. Accordingly, the alkali metal halide solution may include various combinations of the alkali metal component and the halide component exemplified above. As an example, when the halide is Cl, the internal trap of the perovskite photoactive layer can be more effectively passivated. In this case, the alkali metal halide solution contains at least one selected from the group consisting of KCl, LiCl, NaCl, and CsCl. It may contain.

The concentration of the alkali metal halide solution may be 1 mM or more, 5 mM or more, or 10 mM or more. In addition, the concentration of the alkali metal halide solution may be 100 mM or less, 30 mM or less, 20 mM or less, or 15 mM or less. For example, the alkali metal halide solution may have an alkali metal halide content of 1 mM to 100 mM. As a specific example, the alkali metal halide solution may have an alkali metal halide content of 10 mM to 15 mM. When it is within the above range, the alkali metal halide may more effectively diffuse into the perovskite precursor coating layer during the annealing process.

The alkali metal halide solution may contain an aqueous solvent, for example deionized water as a solvent.

The method of coating the alkali metal halide solution on the electron transport layer is not particularly limited, but for example, spin coating, dipping, spraying, drop casting, doctor blade ( It can be coated by doctor blade, bar coating, slot die coating, micro gravure coating, coma coating or printing. As a specific example, the alkali metal halide solution may be coated by immersion.

After the alkali metal halide solution is coated, an annealing process may be further performed, and an excess solvent may be removed through this process. In this case, the annealing temperature may be 20°C to 250°C, and specifically 50°C to 200°C, 50°C to 150°C, 50°C to 120°C, or 80°C to 120°C. As described above, the manufacturing method according to the present invention is capable of a low-temperature process.

(2) formation of perovskite photoactive layer

In step (2), a perovskite precursor solution is coated on the previously modified electron transport layer, followed by annealing to form a perovskite photoactive layer.

The perovskite precursor solution may contain a conventional perovskite precursor used in the perovskite solar cell field.

For example, the perovskite precursor may contain a compound represented by the following formula (1).

BX ₂ (1)

In the above formula, B is at least one selected from Pb, Sn, and Ge, and X is a halogen element.

The perovskite precursor solution may contain an oily solvent. As an oily solvent used in the perovskite precursor solution, any solvent capable of dissolving or dispersing the compound of Formula 1 may be used without limitation, specifically dimethylformamide (DMF), dimethyl sulfoxide (DMSO) Or a combination of these may be used.

The method of coating the perovskite precursor solution on the modified electron transport layer is not particularly limited, for example, spin coating, dipping, spraying, drop casting. , Doctor blade (doctor blade), bar coating (bar coating), slot die coating (slot die coating), micro gravure coating (micro gravure coating), coma coating (coma coating) or printing (printing) can be coated. As a specific example, the perovskite precursor solution may be coated by spin coating.

Thereafter, the perovskite precursor coating layer is annealed to form a perovskite photoactive layer.

The annealing may be performed at a temperature of 20°C to 250°C. Specifically, the temperature during the annealing may be 50°C to 200°C, 50°C to 150°C, 50°C to 120°C, or 80°C to 120°C. As described above, the manufacturing method according to the present invention is capable of a low-temperature process.

During the annealing, while the perovskite crystal is formed from the perovskite precursor, the alkali metal halide present in the modified electron transport layer may diffuse and be doped into the perovskite crystal.

Specifically, during the annealing The alkali metal halide contained in the modified electron transport layer may diffuse into the perovskite precursor coating layer.

Accordingly, the alkali metal halide diffused into the perovskite precursor coating layer during the annealing may passivate a trap in the perovskite photoactive layer formed after the annealing.

(3) Other manufacturing steps

Also, prior to the step (1), forming a first electrode layer on the substrate; And forming the electron transport layer on the first electrode layer.

The method of forming the first electrode layer on the substrate may employ a conventional process used in the perovskite solar cell field, for example, thermal evaporation, electron beam evaporation, Sputtering or the like can be used.

In addition, the electron transport layer may be prepared using, for example, a sol-gel method, but is not limited thereto.

In addition, after the step (2), forming a hole transport layer on the perovskite photoactive layer; And forming a second electrode layer on the hole transport layer.

The hole transport layer may be formed through a coating method commonly used in the art after mixing the material for the hole transport layer with a solvent. The solvent may be used without limitation as long as it is a solvent capable of dissolving or dispersing the material of the hole transport layer, and for example, acetonitrile, toluene, xylene, dichloromethane, chloroform, dichlorobenzene, or chlorobenzene.

The method of manufacturing the second electrode layer may be thermal evaporation, sputtering, or the like, but is not limited thereto.

<Perovskite solar cell>

The perovskite solar cell according to the present invention includes a substrate; A first electrode layer; An electron transport layer containing an electron transporter; A photoactive layer containing perovskite; Hole transport layer; And a second electrode layer in a sequentially stacked form, wherein the electron transport layer and the photoactive layer further contain the same alkali metal and halide.

Hereinafter, each component will be described in detail.

The substrate may include a transparent material, and may include, for example, glass, quartz, or conductive plastic.

The first electrode layer may employ a material that can be used for a perovskite solar cell, for example, a transparent electrode material, specifically indium tin oxide (ITO), fluorin tin oxide (FTO), ZnO Materials such as -Ga ₂ O ₃ , ZnO-Al ₂ O ₃ , tin oxide, and zinc oxide can be used.

The thickness of the first electrode layer may be 100 to 200 nm, but is not limited thereto.

The electron transport layer contains an electron transporter, and the electron transporter may include a metal oxide. The specific types of metal oxides contained in the electron transporter are as exemplified in the method of manufacturing a perovskite solar cell.

In addition, the photoactive layer contains perovskite, and the perovskite may include, for example, one or more of inorganic perovskite and organic-inorganic hybrid perovskite (OIHP).

According to the present invention, the electron transport layer and the photoactive layer further contain the same alkali metal and halide.

The content of the alkali metal in the electron transport layer may be 10% to 20% by weight, and specifically 13% to 18% by weight. In addition, the content of halide in the electron transport layer may be 10% by weight to 30% by weight, and specifically 15% by weight to 25% by weight.

The content of the alkali metal in the perovskite photoactive layer may be 0.001% by weight or more, 0.1% by weight or more, or 0.5% by weight or more, and may be 5% by weight or less, 1.5% by weight or less, or 0.5% by weight or less. For example, the content of the alkali metal in the perovskite photoactive layer may be 0.001 wt% to 0.1 wt%, 0.1 wt% to 5 wt%, 0.1 wt% to 0.5 wt%, or 0.5 wt% to 1.5 wt% have.

In addition, the halide content in the perovskite photoactive layer may be 0.001% by weight or more, 0.1% by weight or more, or 0.5% by weight or more, and may be 5% by weight or less, 2% by weight or less, or 0.5% by weight or less. For example, the content of halide in the perovskite photoactive layer may be 0.001% by weight to 0.1% by weight, 0.1% by weight to 5% by weight, 0.1% by weight to 0.5% by weight, or 0.5% by weight to 2% by weight. .

The specific types of the alkali metal and halide are as exemplified in the method of manufacturing a perovskite solar cell above.

For example, the electron transporter includes a metal oxide, the alkali metal includes at least one selected from the group consisting of K, Li, Na, and Cs, and the halide is composed of F, Cl, Br, and I. It may include at least one selected from the group. Accordingly, the alkali metal halide solution may include various combinations of the alkali metal component and the halide component exemplified above.

_{Specifically, the electron transporter is a group consisting of ZnO, SnO 2} , TiO ₂ and Al ₂ O ₃ doped or undoped with at least one selected from the group consisting of Al, Mg, In, Zn, Ga, and Sr. Contains one or more metal oxides selected from, the alkali metal contains K, the halide contains Cl, and the perovskite is an inorganic perovskite and an organic-inorganic hybrid perovskite (OIHP ) May contain one or more of.

As a more specific example, the electron transporter includes ZnO, the alkali metal includes K, the halide includes Cl, and the perovskite includes an organic-inorganic hybrid perovskite (OIHP). can do.

The organic-inorganic hybrid perovskite may include a compound represented by Formula 2 below.

ABX ₃ (2)

In the above formula, A is an alkyl group containing any one substituent selected from an amino group, a hydroxyl group, a cyano group, a halogen group, a nitro group and a methoxy group, B is at least one selected from Pb, Sn, and Ge, and X is a halogen element to be.

Specifically, A may be an alkyl group including an amino group, B may be Pb, and X may be I.

The material of the hole transport layer is not limited as long as it is a material used in the field of perovskite solar cells. For example, poly(3-hexylthiophene) (P3HT), poly[2,1,3-benzothiadiazole -4,7-diyl[4,4-bis(2-ethylhexyl-4H-cyclopenta[2,1-b:3,4-b']dithiophene-2,6-diyl)]](PCPDTBT) , Poly[[9-(1-octylnonyl)-9H-carbazole-2,7-diyl]-2,5-thiophendiyl-2,1,3-benzothiadiazole-4,7-diyl- 2,5-thiophendiyl] (PCDTBT), poly(triarylamine) (PTAA), 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]- It may be 9,9'-spirobifluorene (Spiro-OMeTAD).

The material of the second electrode layer is not limited as long as it is a material used in the field of perovskite solar cells, for example, Pt, Au, Ni, Cu, Ag, In, Ru, Pd, Rh, Ir, conductive polymer, Or it may be a combination of these.

The perovskite solar cell according to the present invention has high power conversion efficiency, long-term stability and very little hysteresis. Specifically, the perovskite solar cell has a power conversion efficiency (PCE) of 21% or more, and a hysteresis index of 7% or less for photocurrent, and after storage at room temperature for 1400 hours, 80% or more compared to the initial stage. Power conversion efficiency can be maintained.

In addition, the perovskite solar cell according to the present invention can be manufactured by a low-temperature process, so that a plastic substrate can be used, and as a result, it can be improved in terms of flexibility. Specifically, in the perovskite solar cell, the substrate includes a plastic material, and the perovskite solar cell may maintain a power conversion efficiency of 70% or more compared to the initial stage after 1000 bending cycles.

In addition, the electron transport layer is modified by an alkali metal halide, the photoactive layer is formed by annealing the perovskite precursor coating layer, the alkali metal halide diffuses into the perovskite precursor coating layer, the annealing The trap in the perovskite photoactive layer formed later can be passivated.

[Example]

The present invention will be described in more detail by the following examples. However, the scope of the present invention is not limited by these examples.

The meanings of the abbreviations used in the examples and related drawings are as follows.

AM: air mass

AR: anti-reflection

DLCP: drive-level-capacitance profiling

DMF: dimethylformamide

DMSO: dimethylsulfoxide

DOS: density of states

EDS: electron dispersive spectroscopy

EQE: external quantum efficiency

ETL: electron transport layer

FA: formamidium

FE-SEM: field emission scanning electron microsope

FF: fill factor

FIB: focused ion beam

FWHM: full width at half maximum

HAABF: high-angle annular bright-field

HTL: hole transport layer

IMPS: intensity-modulated photocurrent spectroscopy

IMVS: intensity modulated photovoltage spectroscopy

IPA: isopropanol

ITO: indium tin oxide

KCl-OIHP: OIHP modified with KCl

L-PSC: low-temperature processed PSC

L-PSC-LiCl, L-PSC-NaCl, L-PSC-KCl and L-PSC-CsCl: L-PSC modified with LiCl, NaCl, KCl and CsCl, respectively

MA: methylammonium

MPP: maximum power point

OIHP: organic-inorganic hybrid (or halide) perovskite

PCE: power conversion efficiency

PEN: polyethylene naphthalate

PL: photoluminescence

PMT: photon multiplier tube

PSC: perovskite solar cell

SEM: scanning electron microscopy

Spiro-OMeTAD: 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino-9,9'-spirobifluorene

ST-PL: steady-state photoluminescence

TAS: thermal admittance spectroscopy

TEM: transmission-electron-microscopy

TCSPC: time-correlated single photon counting

tDOS: trap density of states

TPC: transient photocurrent

TPV: transient photovoltage

TRPL: time-resolved photoluminescence

UPS: ultraviolet photoelectron spectroscopy

ZnO-ETL: ETL composed of ZnO

ZnO-LiCl, ZnO-NaCl, ZnO-KCl and ZnO-CsCl: ZnO modified with LiCl, NaCl, KCl and CsCl, respectively

XPS: X-ray photoelectron spectroscopy

XRD: X-ray diffraction

Experiment summary

In the following examples and experimental examples, through simultaneous doping of alkali metal and Cl at the OIHP crystal and ZnO/OIHP interface, a high-efficiency ZnO-based L-PSC having improved long-term stability and very little hysteresis was implemented. In addition, by monitoring the trap-state distribution, it was confirmed that the long-term stability was improved and the effective passivation of the deep trap was observed.

As a result, the annealing after modification of the ZnO/OIHP interface using alkali metal chloride successfully diffused the alkali metal and Cl into the OIHP photoactive layer to passivate the shallow trap and deep trap states. In addition, the effective passivation of shallow and deep traps at the OIHP crystal and ETL/OIHP interface improved the long-term stability of L-PSC and significantly reduced hysteresis.

Accordingly, PCE, photocurrent hysteresis and long-term stability of ZnO-based L-PSC were simultaneously improved, and specifically, KCl-modified L-PSC (L-PSC-KCl) achieved very little photocurrent hysteresis and PCE of 22.3%.

In particular, L-PSC-KCl exhibited excellent long-term stability in the atmosphere (> 90% of the initial PCE after 1400 hours) due to the efficient passivation of the deep trap, which is less than 10% of the initial PCE after the unmodified control (> 1400 hours). It is much improved compared to Yuji).

In addition, a flexible L-PSC using an ITO/PEN substrate was also manufactured by taking advantage of the low-temperature processability according to the present invention. ) Was confirmed.

material

Zinc acetate dihydrate, ethanolamine, 2-methoxyethanol, alkali chloride, isopropanol (IPA), dimethyl formamide (DMF) and dimethyl sulfoxide (DMSO) used in the examples were all purchased from Sigma Aldrich. I did. Formamidium iodide (FAI), methyl-ammonium bromide (MABr) and methyl-ammonium iodide were purchased from Greatcellsolar. Lead(II) iodide was purchased from Alfa Aesar. Spiro-OMeTAD was purchased from Borun New Material.

Example 1. Manufacture of perovskite solar cell (PSC)

The anti-reflective coated ITO/glass substrate was sequentially washed with acetone and IPA for 15 minutes, respectively, and washed with ultraviolet ozone for 20 minutes. Then, a ZnO sol-gel solution was spin-coated on the ITO/glass substrate (2000 rpm, 15 seconds), and annealed at 130° C. for 30 minutes to form a ZnO layer having a thickness of 40 nm. In a solution in which an alkali metal chloride (LiCl, NaCl, KCl or CsCl) is dissolved in deionized water in a concentration range of 0-15 mM, the previously formed ZnO layer is immersed for 1 minute, and then the ZnO layer is simply washed with deionized water. , Annealed at 100° C. for 10 minutes to remove excess solvent.

Subsequently, an OIHP layer based _{on MA x} FA _1-x Pb(I _x Br _1-x ) ₃ was formed on the modified ZnO-ETL. 1.5 mM PbI ₂ solution (DMF/DSMO (9:1) solvent) was heated at 75° C. overnight, spin-coated (2500 rpm, 30 seconds) on the modified ZnO layer obtained previously, and then annealed at 80° C. for 2 minutes. Thus, a PbI ₂ layer was formed. After cooling to room temperature, the PbI ₂ layer was immersed in a mixed solution of FAI/MAI/MABr (2700 mg:120 mg:120 mg in 30 mL IPA) and annealed at 80°C for 2 minutes to form a perovskite layer. I did. After cooling, IPA was drop-casted on the perovskite layer (4000 rpm, 20 seconds) to wash, then annealed at 120° C. and treated under ^{vacuum (10 -4 Torr) for 20 minutes.}

The treated samples were transferred to a nitrogen gas filled glove box for the next process. A solution of hole transport (spiro-OMeTAD) (65 mg/mL) in 1 mL chlorobenzene was spin coated (4000 rpm for 30 seconds). This solution contained 70 μL of bis(trifluoromethane)sulfonimide lithium (Li-TFSI; 170 mg/mL in acetonitrile) and 20 μL of tert-butylpyridine (TBP) as additives. For the final step, a 100 nm thick Au layer was evaporated at ^{low pressure (< 10 -6 Torr).}

For subsequent tests, the active area was set to a large area (1.12 cm ² ) or a small area (0.0518 cm ² ) using a black metal mask.

Experimental Example 1. Alkali metal chloride modification

In this experimental example, it was evaluated that the ZnO/OIHP interface was passivated by modifying the surface of ZnO-ETL with an alkali metal chloride (LiCl, NaCl, KCl, CsCl) solution. Through EDS mapping of the SEM image (see Fig. 1A) and XPS analysis (see Fig. 7), uniform modification across the entire ZnO surface was confirmed. The shift of the Zn 2p XPS peak to a higher binding energy indicated that Cl was directly bound to Zn (see H in FIG. 7). The contents of alkali metal (14.5±0.2%, see G in FIG. 7) and Cl (19.6±0.4%, F in FIG. 7) in the modified ZnO-ETL were similar in all samples.

Oxygen-deficient ZnO defects were found in the O 1s XPS spectrum (see A to F in Fig. 8). The significantly reduced intensity of the higher binding energy peaks in the modified ZnO layer indicated effective passivation of oxygen-deficient defects. At the visible wavelength (450-700 nm), the PL emission associated with the ZnO defect was substantially reduced by the modification (see G in FIG. 8). The defect-related reduction in PL emission was most pronounced in the ZnO (ZnO-KCl) samples modified with KCl. _{For comparison, a sample of NH 4} Cl modified ZnO-ETL (ZnO-NH ₄ Cl) with similar Cl incorporation but no alkali metal was prepared. ZnO-NH ₄ Cl showed a similar Cl doping level (see FIG. 7 F), but showed the highest visible PL emission among the modified ZnO-ETLs. This indicates that due to the simultaneous modification of the alkali metal and Cl, a much more efficient interfacial defect passivation occurred compared to the case of Cl alone.

The table below summarizes the performance of L-PSC-KCl under various reforming conditions.

L-PSC-KCl PCE (%) V _OC (V) J _SC (mAcm ^-2 ) FF(%) 0 mM 18.4 1.12 22.4 73 2 mM 19.5 1.13 23.0 76 10 mM 21.2 1.15 23.3 79 15 mM 21.6 1.15 23.5 80 20 mM 19.6 1.14 22.7 76

In Example 1, an _{OIHP layer based on MA x} FA _1-x Pb (I _x Br _1-x ) ₃ was formed on the modified ZnO through a two-step inter-diffusion deposition method. Steady state PL emission spectra and TCSPC analysis results showed improved charge transfer in the modified ZnO/OIHP due to interfacial defect passivation (see Fig. 9 and Table 1). In particular, the OIHP layer prepared on the modified ZnO showed larger crystal grains as can be seen in the SEM image (see Fig. 10). The average particle size of the KCl modified OIHP sample was about 450 nm, and the average particle size of the unmodified sample was about 300 nm. In addition, in the X-ray diffraction (XRD) spectrum, the modified OIHP samples showed more developed (110), (220), (310) perovskite peaks with _{smaller (001) PbI 2 peaks (Fig.} 1, B).

The half-value full width (FWHM) of the perovskite (110) peak measured from a sample modified with LiCl, NaCl, KCl or CsCl was 0.24±0.02°, 0.22±0.02°, 0.18±0.02°, and 0.19±0.02°, respectively. , The control sample value was 0.28±0.02° (see Fig. 11), which is dependent on the crystal grain size from the SEM image. From these results, it can be seen that the alkali chloride modification actually affects the quality of the OIHP layer. In particular, a clear shift of the (310) perovskite crystal plane peak to lower the 2θ value in the modified sample was confirmed (refer to the right figure B of FIG. 1). This lattice expansion appears to result from the occupancy of the pores of alkaline cations within the OIPH crystal lattice.

The parameters of the TCSPC analysis are summarized in the table below.

division TCSPC analysis τ ₁ ( f ₁ )/ns τ ₂ ( f ₂ )/ns ZnO/OIHP 7.21/0.51 147.71/0.49 LiCl 6.61/0.56 109.05/0.44 NaCl 4.19/0.77 105.36/0.23 KCl 2.73/0.86 96.24/0.14 CsCl 3.49/0.79 87.30/0.21

As can be seen from the TEM and EDS mapping results (see C in FIG. 1), both K and Cl atoms were effectively diffused throughout the modified OIHP layer, but no K or Cl atoms were detected in the control sample (see FIG. 12). To further confirm the distribution, XPS depth profiling of the samples was performed. The penetration of K and Cl atoms throughout the OIHP layer was confirmed as can be seen in FIG. 1D. The diffusion of K and Cl atoms was dependent on the concentration of the modified KCl solution. In the modified sample using a low concentration KCl solution (2 mM), K and Cl could not penetrate into the OIHP layer and were mainly present at the ZnO/OIHP interface (see Fig. 13). This result showed that residual KCl on the ZnO layer diffused into the OIHP layer during the OIHP annealing step.

Experimental Example 2. Effect of Modification on Interface and Internal Trap Site

PL emission mapping was used to investigate the effect of the modification on trap passivation in the OIHP layer. The KCl-modified OIHP layer (KCl-OIHP) on the glass substrate had a higher PL emission intensity (red) compared to the unmodified sample (blue) due to inhibition of non-radioactive recombination caused by the trap state (Fig. 2A Reference). The PL emission images showed uniform modification over a relatively large area (20 μm×20 μm) in both samples. In addition, the blue-shift of PL emission was observed in the KCl-OIHP sample due to trap state passivation as shown in FIG. 15B (see FIG. 15A). As shown in Fig. 15C and D, the PL emission of the unmodified sample was most at 817 nm, while the PL emission of the KCl modified sample was at 811 nm. This blue shift is due to the internal trap state passivation by KCl modification. In addition, the TCSPC analysis results (see FIG. 2B) showed a reduction in trap due to a longer PL decay life in KCl-OIHP (195.9 ns) compared to unmodified OIHP (89.1 ns). The tDOS of the OIHP layer was quantified using DLCP, a well-established technique in semiconductor thin films. 2C showed that the tDOS in the low-modulated frequency domain of the KCl-OIHP layer was lower than that of the unmodified control sample (1.2×10 ¹⁸ cm ⁻³ ) (1.1×10 ¹⁷ cm ⁻³ ). . These results suggest that the diffusion of K and Cl and the occupancy of the gaps effectively reduced the internal trap state of the OIHP layer. 16 is a JV curve of L-PSC-KCl modified under various conditions, it can be seen that KCl modification is excellent in a solution concentration range of 10 to 15 mM.

Experimental Example 3. Performance of L-PSC

A planar structure L-PSC device (ITO/ZnO/OIHP/spiro-OMeTAD/Au, see FIG. 3A) was fabricated and characterized. All deposition processes were performed at less than 130° C. in air. The PCE of the unmodified L-PSC was 19.4% under reverse scan with a stabilized power output of 18.9%, which was comparable to that of other reported ZnO based PSCs. The PCE of L-PSC modified with alkali metal chloride was substantially improved (see Fig. 3C and Table 1). KCl-modified L-PSC (L-PSC-KCl) achieved a maximum PCE of 22.3% (V _OC 1.16 V, J _SC 23.9 mAcm ^-2 , FF 80%), and the EQE in the entire visible region was also higher than before. (See Fig. 17). In particular, the V _OC loss of L-PSC-KCl (E _g / q - V _OC ) (where E _g is the band gap of the EQE cutoff (1.52 eV) and q is the basic charge) was only 0.36 V. This is one of the lowest V _OC loss values among the reported PSCs. The J _SC value of the JV analysis was inconsistent with <1%, and was in good agreement with the calculated J _SC value of the EQE analysis, confirming the reliability of the analysis result. Table 3 below summarizes the performance evaluation results of L-PSC. Statistical analysis results of V _OC and PCE values from 30 samples are shown in Fig. 3E and Fig. 3F, respectively.

division PCE (%) V _OC (V) J _SC (mAcm ^-2 ) FF(%) Integrated J _SC from EQE (mAcm ^-2 ) Control L-PSC 19.4 1.12 23.2 74 22.9 L-PSC-LiCl 20.9 1.14 23.6 77 23.3 L-PSC-NaCl 21.2 1.15 23.7 77 23.5 L-PSC-KCl 22.3 1.16 23.9 80 23.8 L-PSC-CsCl 21.8 1.16 23.9 78 23.7

The effect of internal and interfacial trap passivation on the charge collection characteristics of PSC was revealed through various analysis techniques. TPV/TPC spectroscopy was performed to determine charge recombination lifetime (τ _rec ) and charge transport time (τ _ct ). The TPV/TPC analysis results are summarized in Table 4 below. As shown in Table 4 below, the modified L-PSC showed a longer τ _rec and a shorter τ _ct duration than the unmodified L-PSC. _{Τ rec} of L-PSC-KCl was 1.69 times longer (204 μs) than that of unmodified L-PSC (121 μs), whereas τ _ct of L-PSC-KCl was 1.29 than that of unmodified L-PSC (2.2 μs). It was fold short (1.7 μs). These results indicate that trap passivation (internal and interfacial) by alkali metal chloride modification effectively improved the charge extraction of L-PSC.

division _{Τ rec} from TPV (μs) _{Τ ct} from TPC (μs) Control L-PSC 121 2.2 L-PSC-LiCl 172 2.0 L-PSC-NaCl 187 1.9 L-PSC-KCl 204 1.7 L-PSC-CsCl 196 1.8

In particular, L-PSC-KCl achieved significantly lower photocurrent hysteresis compared to unmodified L-PSC (see Fig. 20). Hysteresis was analyzed by measuring PCE in both the reverse and forward scan directions and calculating the HI index using the following equation:

The hysteresis index measurement results are summarized in Table 5 below. As shown in Table 5 below, the HI-index of L-PSC-KCl achieved 0.9%, while the unmodified L-PSC was 9.4%. The HI index (0.9%) of L-PSC-KCl was one of the lowest reported PSCs.

division Scan direction PCE (%) V _OC (V) J _SC (mAcm ^-2 ) FF(%) H-index (%) Control L-PSC Reverse 19.1 1.12 23.2 73 9.4 Forward direction 17.3 1.05 23.2 72 L-PSC-LiCl Reverse 20.8 1.14 23.7 77 5.8 Forward direction 19.6 1.11 23.5 75 L-PSC-NaCl Reverse 21.0 1.14 23.8 78 4.8 Forward direction 20.0 1.11 23.8 76 L-PSC-KCl Reverse 22.2 1.15 24.0 80 0.9 Forward direction 22.0 1.15 23.9 79 L-PSC-CsCl Reverse 21.8 1.15 23.9 79 1.4 Forward direction 21.5 1.14 23.8 79

Experimental Example 4. Effect of alkali chloride on photocurrent hysteresis

Photocurrent hysteresis is often caused by charge accumulation at the interface due to trapping and de-trapping of charge carriers. To evaluate the charge accumulation at the ZnO/OIHP interface of the L-PSC, the capacitance-voltage ( C _p -V ) was measured at various illuminances (see A and B in Fig. 4). In relation to the illuminance , the shift of the peak potential (V _peak ) under reverse bias reflected the degree of interfacial charge accumulation, which was due to interfacial charge trapping as shown in FIG. 4D. The slight shift of V _peak in L-PSC-KCl (see Fig. 4B) resulted in lower charge accumulation (smaller charge trapping) compared to unmodified L-PSC (larger V _{peak shift), which is L-} It led to a significant reduction in photocurrent hysteresis in PSC-KCl.

In order to study the effect of modification on the ion migration behavior, an activation energy ( E _a ) for ion migration was determined using a temperature-dependent conductivity measuring device (see FIG. 21). Conductivity values at various temperatures were extracted from the IV curve in dark conditions, and then the activation energy was calculated from this using the following Nernst-Einstein equation:

Where k is the Boltzmann constant, σ _o is the constant, and T is the temperature.

The E _a value of the control unmodified sample was 0.17 eV, similar to the previously reported value, whereas the E _a value of the KCl modified sample increased to 0.23 eV, a significant improvement of the energy barrier to ion migration in the modified OIHP layer. Showed.

To further investigate the distribution in the trap-state, TAS was performed. The t DOS profiling from TAS was well established and effectively showed the distribution of shallow traps and deep traps in the thin film. Figure 5A shows the t DOS ( expressed as N _T ) versus the energy defect level from TAS, which was calculated from the following equation:

Here, C is the capacitance, ω is the angular frequency, q is the fundamental charge, k _B is the Boltzmann constant, and T is the temperature. V _bi and W are the built-in potential and depletion width in the space charge region, respectively, obtained from the Mott-Schottky curve of FIG. 22. The energy defect level was defined as the applied angular frequency dependence:

Here, w ₀ is the angular frequency of the escape attempt.

Experimental Example 5. Trap State and Stability Analysis

In Fig. 5A, band 1 is associated with shallow traps, while bands 2 and 3 are for deep traps. Shallow traps have been reported to be associated with grain boundary traps, while deeper traps between regions have been reported to correspond to surface defects. The trap density of the control sample was much higher than that of the modified sample in both the shallow and deep trap areas (10 ¹⁷ -10 ¹⁸ cm ^-3 ). L-PSC-KCl showed the lowest trap density (shallow and deep), indicating that the double passivation effect by K and Cl was most efficient for passivation of traps in the interface and OIHP crystals. 23 shows the trap density by TPV/TPC analysis. The KCl modification-based samples showed the lowest trap density state in both results, indicating the consistency of trap state reduction by KCl modification using various methods. The t DOS values determined by various techniques such as DLCP (see C in Fig. 2) and TPV/TPC analysis (see Fig. 23 and Table 6) were in good agreement with the TAS analysis results. The trap state densities obtained from TPV/TPC analysis are summarized in the following table.

division Trap state density from TPV/TPC (cm ^-3 /eV) Control 3.8×10 ¹⁷ LiCl 2.1×10 ¹⁷ NaCl 2.1×10 ¹⁷ KCl 1.6×10 ¹⁷ CsCl 1.6×10 ¹⁷

The effect of modifying on the long-term stability of L-PSC was also tested. As shown in Fig. 24, it was confirmed that the reverse decomposition reaction was suppressed by the modification. In the long-term shelf life test, the L-PSC was not encapsulated and the ^{PCE was measured under 100 mWcm -2} illumination (AM 1.5G one sun illumination) in atmospheric conditions (see Fig. 5D). L-PSC-KCl maintained 90% of the initial PCE even after 1400 hours, while the unmodified L-PSC remained below 10%. A thermal stability test was performed by placing the sample on a hot plate at 70° C. in a glove box filled with nitrogen. L-PSC-KCl maintained more than 75% of the initial PCE even after exceeding 200 hours (see E of FIG. 5), which was significantly better than the unmodified L-PSC (<13% maintenance). In addition, L-PSC ^{was placed under continuous MPP conditions in a nitrogen-filled glove box under white LED light (100 mWcm -2} , one sun illumination) to evaluate long-term light stability under light-immersion conditions. L-PSC-KCl retained 76% of the initial PCE even after 150 hours, whereas the unmodified L-PSC completely lost its performance (see F in FIG. 5).

TAS analysis was used to monitor the distribution of trap states to further investigate the cause of the improved long-term stability of L-PSC-KCl. After storage under the atmosphere for 2 weeks, the deep trap state (band 2, 0.40 to 0.50 eV) in the control sample rapidly increased, resulting in interfacial failure, while the shallower trap state was slightly changed (see FIG. 5B). . In particular, L-PSC-KCl showed almost the same trap state distribution even after storage under the atmosphere for 2 weeks (see Fig. 5C). This result indicates that the deterioration in the initial stage is mainly due to the formation of the interfacial trap state, and effectively suppressing the deep trap state is an important factor in improving the long-term stability in the atmosphere.

Experimental Example 6. Large-area L-PSC modified with KCl

In the same manner as in Example 1, an L-PSC having an active area ^{of 1.12 cm 2 was prepared.} The PCE of the large-area L-PSC-KCl reached 21.3% with a HI index of 1.4% (see A and Table 7 in Fig. 6), which is the most reported L-PSC so far with an ^{active area> 1 cm 2.} It was one of the high values. In L-PSC-KCl, the PCE difference between the large area sample (21.3%, 1.12 cm ² ) and the small area sample (22.3%, 0.0518 cm ² ) was only 4.5% (this is one of the lowest gaps reported among PSCs). ), it confirmed the uniformity of the modification technique. The following table summarizes the performance of the large-area L-PSC measured in the forward and reverse scan directions.

Large area sample (1.12cm ² ) Scan direction PCE (%) V _OC (V) J _SC (mAcm ^-2 ) FF(%) H-index (%) Control L-PSC Reverse 16.8 1.08 22.9 68 9.5 Forward direction 15.2 1.05 22.7 64 L-PSC-KCl Reverse 21.3 1.15 23.7 78 1.4 Forward direction 21.0 1.15 23.6 78

In addition, in order to demonstrate the advantage of low-temperature processability, a flexible L-PSC was manufactured using an ITO/PEN substrate. PCE of 19.6% was achieved in the flexible L-PCS-KCl, which is significantly higher than that of the existing flexible PSC (see FIG. 6D). In addition, flexible L-PSC exhibited very little photocurrent hysteresis (HI index = 2.6%, see Table 8) after 1000 bending cycles at a bending radius of 6.9 mm, maintaining a PCE of 80% or more compared to the initial stage (Fig. 6). E). Leaded L-PSCs known to date were prepared through vacuum treatment (plasma-enhanced atomic layer deposition, PEALD) and had a high photocurrent hysteresis (HI index = 6.8%) with a PCE of 18.4%. The following table summarizes the performance of flexible L-PSC-KCl measured in the forward and reverse scan directions.

Flexible sample Scan direction PCE (%) V _OC (V) J _SC (mAcm ^-2 ) FF(%) H-index (%) L-PSC-KCl Reverse 19.6 1.14 23.3 74 2.6 Forward direction 19.1 1.14 23.0 73

tester

The test apparatus used in the above Examples and Experimental Examples is as follows.

XPS measurement was performed using a system equipped with a monochromatic Mg Kα line (MultiLab 2000, THERMO VG SCIENCE) at hν = 1253.6 eV (the single pressure is 1×10 ^{-9 Pa).} UPS results were obtained using a system (AXIS-NOVA, Kratos) with a base pressure of 5×10 ^{−8 Torr and with HeI (21.22 eV).} FE-SEM images were obtained using JSM-7610F (JEOL). A cross-sectional sample was obtained using FIB (JIB-4601F). TEM observation was performed in TEM-HAABF mode at an acceleration voltage of 120 kV, respectively, in imaging mode (0.23 nm resolution) and EDS mode using JEM-F200. ST-PL measurements were performed using a SPEX Nanolog 3-21 (Horriba) equipped with a UV-Vis PMT detector (FL-1073/R928). XRD was performed using Ultima IV (RIGAKU) with a Cu Kα (λ=0.1542 nm) line. TRPL curves were recorded using a commercially available TCSPC system (FluoTim 2000, PicoQuant). All samples were photo-excited with a picosecond diode laser (LDH-PC-670, PicoQuant) with a wavelength of 670 nm and a repeatability of 800 kHz. The emitted light was spectrally dispersed with a monochromatic (ScienceTech 9030) and collected by a high-speed PMT detector (PMA 182, PicoQuant). JV characteristics were ^{measured using a Keithley 2401 source unit under 100 mWcm -2} illumination (AM 1.5 G, Newport). Spectral mismatch was corrected using a mono-silicon standard cell (Newport) covered with a KG-5 filter (603621 Calibrated Silicon and Germanium Reference Detector). All samples were tested under atmosphere with reverse and forward scans ( ^{scan speed of 100 mVs -1).} The EQE spectrum was obtained by passing the output of a 400 W xenon lamp through a monochromatic meter and filter. The capacitance-voltage ( C _p -V ) and Mott-Schottky measurements were performed by using an impedance analyzer (Ivium Stat.) under dark conditions and setting the AC signal to a frequency of 1 kHz. IMVS was performed using an impedance analyzer (Ivium Stat.) under green LED illumination (λ=535 nm). The average recombination time (τ _rec ) for the photogenerated charge was obtained from the IMVS curve at the minimum frequency (τ _rec = 1/2π f _min ) in the imaginary part. Electrical polling was performed by applying different biases to samples with electrodes (500 μm intervals) for 1 minute in dark conditions, and current-voltage was measured with a Keithley 2401 source. Temperature dependence was measured using a CTI cryogenic probe station with a temperature controller (Lakeshore 331) attached under vacuum (1×10 ^{-4 Pa).} The temperature was monitored using a thermocouple in contact with the sample. During the measurement, the sample was first cooled to 10 K for 10 minutes and then heated to adjust the temperature. The temperature was allowed to stabilize for 5 minutes before recording the current for each step. TAS was performed using an impedance analyzer (Ivium Stat.). Electrical contact with the sample and measurements were performed with a CTI cryogenic probe station equipped with a temperature controller (Lakeshore 331) under ^{vacuum (1×10 −4 Pa).} TPV and TPC measurements were measured using a self-made system, nanosecond laser (10 Hz, NT342A-10, EKSPLA) and Xe lamp (150 W, Zolix) equipped with a digital oscilloscope (DSO-X 3054A, Agilent) as light source. ) Was used. Voltage/current transitions were obtained using a DPO 3052 Tektronix digital phosphor oscilloscope (1 MΩ for TPV and 10 Ω for TPC).

Stability test method

The samples prepared in the above examples were stored in a dark condition under the atmosphere in an unencapsulated state. The samples were ^{measured for over 1400 hours under 100 mWcm -2} illumination (AM 1.5G one sun illumination). The recorded relative humidity was in the range of 40±5% and the temperature was 25±3°C. After each measurement test, the samples were stored again in dark conditions. Continuous thermal stability tests were performed in a nitrogen filled glove box. The sample was placed on a hot plate at the set temperature and maintained at 70°C.

Alternatively, the sample ^{was measured for 200 hours under 100 mWcm -2} illumination (AM 1.5G one sun illumination). After measurement, the sample was placed back on the hot plate. Continuous light stability tests were performed in simulated white LED light (Newport) conditions without filters and continuous MPP tracking. Measurements were performed in a nitrogen filled glove box using a source meter (Keithley 2401), and the measured temperature was about 45°C. Prior to the stability test, it was purged with nitrogen flow for 15 minutes.

Trap-Density State Analysis

1. Transient optical voltage/photocurrent (TPV/TPC) method

Photocurrent transients for the same pulse were measured under short circuit conditions to determine the trap density state. The open circuit transient voltage was induced by a short change in the incident power at a given optical bias. Thereafter, the change in charge density was determined by integrating the photocurrent transition only with the laser pulse. This change in charge corresponds to the charge stored in most films under the assumption that exciton generation is independent of the applied bias and recombination in the short-circuit current is negligible. The trap density state (t DOS) for each open circuit voltage was obtained by integrating the capacitance to voltage using the following equation ( t DOS is related to the number of intermediate gap states to be filled).

In the above equation, A is the sample area, e is the fundamental charge of the electron, and C is the capacitance.

2. Drive-level capacitance profiling (DLCP)

Density of states (DOS) values were also obtained using other methods based on capacitance and frequency dependence. The capacitance was obtained by varying the amplitude, and in order to achieve the correct capacitance value at a higher order, the following equation was used:

After calculating the values C ₀ and C ₁ , DOS was obtained by the following equation:

In the above equation, A is the sample area, e is the fundamental charge of the electron, and εr is the dielectric constant.

3. Thermal Admittance Spectroscopy (TAS)

The trap state density ( t DOS) can also be obtained from the angular frequency dependent capacitance, which can be used to analyze shallow and deep t DOS simultaneously. t DOS is extracted by reducing the measured capacitance at various angular frequencies. The defect dependent capacitance is obtained by charging and discharging the trap at various angular frequencies in the space charge region. t DOS can be calculated quantitatively using the following equation:

In the above equation, N T is the trap density, C is the capacitance, ω is the angular frequency, q is the fundamental charge, k _B is the Boltzmann constant, and T is the temperature. V bi and W are the intrinsic potential and depletion width in the space charge region, respectively, and these were extracted from the Mott-Schottky curve. The fault energy level is defined as the applied angular frequency dependence.

V _bi was obtained from the Mott-Schottky curve using the following equation:

Depletion width was calculated using the following equation:

In the above equation, εγ is the dielectric constant of the perovskite, N _d is the doping density, e is the basic charge of the electron, and V _bi is the built-in potential of the sample, which was obtained in FIG. 22.

Claims (13)

(1) forming a modified electron transport layer by coating an alkali metal halide solution on the electron transport layer; And
(2) coating a perovskite precursor solution on the modified electron transport layer and then annealing the perovskite precursor coating layer to form a perovskite photoactive layer. Manufacturing method.
The method of claim 1,
In the step (1), the electron transport layer contains a metal oxide;
The alkali metal halide solution contains at least one selected from the group consisting of F, Cl, Br, and I as a halide.
The method of claim 1,
The alkali metal halide solution of step (1) has an alkali metal halide content of 1 mM to 100 mM, a method of manufacturing a perovskite solar cell.
The method of claim 1,
In the step (2), the annealing is performed at a temperature of 20° C. to 250° C., a method of manufacturing a perovskite solar cell.
The method of claim 1,
At the time of annealing in step (2)
Alkali metal halide contained in the modified electron transport layer is diffused into the coating layer of the perovskite precursor, a method of manufacturing a perovskite solar cell.
The method of claim 5,
At the time of annealing in step (2)
The method of manufacturing a perovskite solar cell, wherein the alkali metal halide diffused into the perovskite precursor coating layer passes through a trap in the perovskite photoactive layer formed after the annealing.
The method of claim 1,
Coating of the alkali metal halide solution of step (1) and
The coating of the perovskite precursor solution in step (2) is spin coating, dipping, spraying, drop casting, doctor blade, and bar coating, respectively. bar coating), slot die coating, micro gravure coating, coma coating or printing.
Board;
A first electrode layer;
An electron transport layer containing an electron transporter;
A photoactive layer containing perovskite;
Hole transport layer; And
Including the second electrode layer in a sequentially stacked form,
The electron transport layer and the photoactive layer further contain the same alkali metal and halide, perovskite solar cell.
The method of claim 8,
The electron transporter includes a metal oxide,
The alkali metal includes at least one selected from the group consisting of K, Li, Na and Cs,
The halide comprises at least one selected from the group consisting of F, Cl, Br and I, perovskite solar cell.
The method of claim 8,
_{The electron transporter is selected from the group consisting of ZnO, SnO 2} , TiO ₂ and Al ₂ O ₃ doped or undoped with at least one selected from the group consisting of Al, Mg, In, Zn, Ga, and Sr. Contains one or more metal oxides,
The alkali metal contains K,
The halide comprises Cl,
The perovskite is an inorganic perovskite and an organic-inorganic hybrid perovskite (OIHP) containing at least one of, perovskite solar cell.
The method of claim 8,
The perovskite solar cell is
Power conversion efficiency (PCE) of 21% or more, and
It has a hysteresis index of 7% or less for photocurrent,
Perovskite solar cell that maintains more than 80% power conversion efficiency compared to the initial stage after 1400 hours storage at room temperature.
The method of claim 8,
The substrate comprises a plastic material,
The perovskite solar cell maintains an initial power conversion efficiency of 70% or more after 1000 bending cycles, perovskite solar cell.
The method of claim 8,
The electron transport layer is modified by an alkali metal halide,
The photoactive layer is formed by annealing of the perovskite precursor coating layer, and the alkali metal halide diffuses into the perovskite precursor coating layer to passivate the trap in the perovskite photoactive layer formed after the annealing. Lobsky solar cell.

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