KR102602858B1 - High-performance perovskite solar cells using as a hole transport layer and Method for manufacturing the same - Google Patents

Abstract

A high-performance perovskite solar cell with high efficiency and stability is disclosed. The high-performance perovskite solar cell includes a first electrode, a hole transport layer formed on the upper surface of the first electrode, and a perovskite structure compound formed on the upper surface of the hole transport layer. It includes a photoactive layer, an electron transport layer formed on the upper surface of the photoactive layer, and a second electrode formed on the upper surface of the electron transport layer. At this time, the hole transport layer is formed by coating the upper surface of the first electrode with a NiO:BN dispersion.

Description

High-performance perovskite solar cells using a hole transport layer and method for manufacturing the same {High-performance perovskite solar cells using as a hole transport layer and Method for manufacturing the same}

The present invention relates to perovskite solar cell technology, and more specifically, to a high-performance perovskite solar cell using a NiO hole transport layer containing boron nitride and a method of manufacturing the same.

Recently, organic-metal halide perrobes have excellent optoelectronic properties such as high absorption coefficient, low exciton binding energy, long electron and hole diffusion distance, fast charge transfer rate, and long photogenerated charge lifetime. Organo-metal halide perovskite (OMHP) is attracting attention as an optoelectronic semiconductor material.

In particular, OMHP enabled the production of thin films with excellent optoelectronic properties through a low-temperature solution process, and perovskite solar cells containing it reported a high efficiency of 25.2%, making it a next-generation solar cell that can replace silicon solar cells. is increasing the feasibility of realization.

Perovskite solar cells are divided into mesoporous structures and planar structures. Planar perovskite solar cells are divided into n-i-p and p-i-n structures depending on the order of the interfacial layer, and recently have p-i-n structures due to scalability and stability issues. Research on perovskite solar cells is progressing more actively.

Planar perovskite solar cells have a structure similar to organic bulk heterojunction solar cells and are composed of multilayer thin films including electron and hole transport layers. In particular, the p-i-n structure is a high-performance, large-area perovskite with almost no hysteresis through a low-temperature process. It is considered suitable for commercialization as it can manufacture solar cells.

Various organic and inorganic p-type semiconductors have been used as hole transport layer materials for p-i-n planar perovskite solar cells. Due to the ease of manufacturing process and high efficiency, organic hole transport layer materials such as PEDOT:PSS, PloyTPD, PTAA, etc. are most commonly used in p-i-n planar perovskite solar cells, but the poor stability and high cost of organic materials make them unsuitable for commercialization. don't do it

Accordingly, molybdenum oxide (MoO _x ), tungsten oxide (WO _x ), copper thiocyanate (CuSCN), reduced graphene (rGO), and nickel oxide (NiO _x ). Inorganic hole transport layer materials such as pin planar perovskite solar cells have been applied.

_NiO

However, the photoelectric performance of perovskite solar cells with NiO _x introduced as a hole transport layer is still unsatisfactory due to low short-circuit current density (J _SC ) and fill factor (FF). , it is known that this is due to the low conductivity of the NiO _x film, poor contact with the perovskite, and energy level mismatch between NiO _x and perovskite.

Doping is an effective method to improve the optical and electrical properties of semiconductors. Various doping elements (dopants) such as Cu, Fe, and Cs are used to improve the photoelectric properties such as transparency, band structure, work function, and conductivity of NiO _x . applied.

However, in the above doping method, significant crystal lattice disorders and defects may be caused in the NiO _x crystal, which may reduce charge mobility and cause parasitic recombination.

Moreover, doping complicates manufacturing procedures, narrows the process scope, and increases costs. In particular, doping is difficult if the size of the atom of the doping element is too larger or smaller than the size of the atom of the base phase. Therefore, in order to develop pin planar perovskite solar cells suitable for commercialization, there is no need to solve the problems of existing doping technology. Ultimately, there is a need to form a thin film of a high-quality _NiO

Korean Patent Publication No. 10-2016-0083850

The present invention was proposed to solve the problems caused by the above background technology, and its purpose is to provide a high-performance perovskite solar cell with high efficiency and stability and a method for manufacturing the same.

In addition, the present invention provides _the discovery of an additive that can induce or promote the formation of a high-quality _NiO There is a purpose.

In addition, another object of the present invention is to provide a method for coating a NiO _x NPs dispersion solution containing the above additives.

In order to achieve the problems presented above, the present invention provides a high-performance perovskite solar cell with high efficiency and stability.

The high-performance perovskite solar cell,

first electrode;

a hole transport layer formed on the upper surface of the first electrode;

A photoactive layer formed on the upper surface of the hole transport layer and including a perovskite structure compound;

an electron transport layer formed on the upper surface of the photoactive layer; and

and a second electrode formed on the upper surface of the electron transport layer, wherein the hole transport layer is formed by coating the upper surface of the first electrode with a dispersion liquid.

In addition, the dispersion is a NiO:BN dispersion, and the NiO:BN dispersion is produced by adding 1 vol% to 5 vol% of boron nitride dispersion to the NiO _x dispersion and stirring for a first preset time. Do it as

Additionally, the first constant time is characterized in that it is 23 to 25 hours.

In addition, the _NiO

Additionally, the second constant time is characterized in that it is 3 to 4 hours.

Additionally, the coating is performed at 3,500 to 4,500 rpm (revolutions per minute) for 35 to 45 seconds.

In addition, the compounds of perovskite structure are CH ₃ NH ₃ PbI _3-x Cl _x (real number with 0≤x≤3), CH ₃ NH ₃ PbI _3-x Br _x (real number with 0≤x≤3) , CH ₃ NH ₃ PbCl _3-x Br _x (real number with 0≤x≤3), CH ₃ NH ₃ PbI _3-x F _x (real number with 0≤x≤3), and Cs _1-xy FA _x MA _y Pb(I _1-z Br _z ) ₃ (real number of 0≤x≤1, 0≤y≤1, 0≤1-xy≤1, 0≤z≤1) (where Cs is cesium, FA is Formamidinium, MA is Methylammonium, Pb is Lead, I is Iodide, and Br is Bromide. do.

Additionally, the weight percent concentration of the perovskite precursor solvent for the above compound is characterized in that it is 20 wt % to 56 wt %.

Additionally, the perovskite precursor solvent includes N,N-Dimethylformamide (DMF), G-butyrolactone (GBL), N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), and N,N-dimethylacetamide (DMAc). It is characterized in that it is one of the following polar solvents or a mixed solvent mixed with the above polar solvents.

In addition, the photoactive layer is formed using a perovskite precursor solution, and the perovskite precursor solution includes formamidinium iodide (FAI), methylammonium bromide (MABr), and A solute mixed with Cesium Iodide (CsI), Lead Bromide (PbBr ₂ ), and Lead Iodide (PbI ₂ ) in a ratio of Cs _0.175 FA _0.750 MA _0.075 Pb (I _0.880 Br _0.120 ) ₃ and Dimethylformamide (DMF): It is characterized by being composed of a mixed solvent of dimethyl sulfoxide (DMSO) = 8:2.

In addition, the perovskite precursor solution is first coated on the upper surface of the hole transport layer at 500 to 550 rpm for 4 to 6 seconds, and then secondarily coated at 4,500 to 5,500 rpm for 40 to 50 seconds. .

In addition, the coating is characterized in that it is one of spin coating method, spray coating method, slot die coating method, bar coating method, and doctor blade method.

On the other hand, another embodiment of the present invention includes (a) preparing a first electrode; (b) forming a hole transport layer on the upper surface of the first electrode; (c) forming a photoactive layer containing a perovskite structure compound on the upper surface of the hole transport layer; (d) forming an electron transport layer on the upper surface of the photoactive layer; and (e) forming a second electrode on the upper surface of the electron transport layer, wherein the hole transport layer is formed by coating the upper surface of the first electrode with a dispersion liquid. A method for manufacturing a perovskite solar cell is provided.

According to the present invention, by mixing a small amount of boron nitride as an additive in the dispersion of the NiO hole transport layer, the formation of a high-quality _NiO A perovskite thin film with particles can be formed.

In addition, another effect of the present invention is that the performance of the device can be improved by lowering the interfacial resistance between the perovskite light absorption layer and the hole transport layer and lowering the recombination of photogenerated charges by traps.

In addition, as another effect of the present invention, it is possible to manufacture a large-area perovskite solar cell with a high efficiency of 20% or more, and the perovskite stability in the air is improved through the additive. One example is that solar cells can be provided.

In addition, another effect of the present invention is that it is possible to prepare an additive that can induce or promote the formation of a high-quality NiO _x- based hole transport layer thin film with excellent photoelectric properties and a NiO _x- based hole transport layer dispersion solution containing the same. points can be mentioned.

In addition, another effect of the present invention is that it is possible to coat a _NiO .

1 is a schematic diagram of a perovskite solar cell according to an embodiment of the present invention.
Figure 2 is a process chart showing the process of preparing a dispersion according to an embodiment of the present invention.
Figure 3 is a process chart showing the process of perovskite solar cell using the dispersion prepared in Figure 2.
Figure 4 is a diagram showing an energy-dispersive X-ray spectroscopy (EDS) element mapping image for a NiO:BN hole transport layer thin film according to an embodiment of the present invention.
Figure 5 is a diagram showing high-resolution X-ray photoelectron spectroscopy (XPS) of a NiO:BN hole transport layer thin film according to an embodiment of the present invention.
Figure 6 is a diagram showing the current-voltage curve and statistics of photoelectric conversion efficiency (PCE) of a perovskite solar cell having a NiO or NiO:BN thin film as a hole transport layer according to an embodiment of the present invention. .
Figure 7 shows the steady-state photocurrent output, external quantum efficiency (EQE), and external quantum efficiency (EQE) at the maximum power point voltage of a perovskite solar cell having a NiO or NiO:BN thin film as a hole transport layer according to an embodiment of the present invention. This is a diagram showing the internal quantum efficiency (IQE).
FIG. 8 is a diagram showing an ultraviolet spectral spectrum of a NiO and NiO:BN hole transport layer thin film and an energy band diagram of a perovskite solar cell including a NiO and NiO:BN hole transport layer according to an embodiment of the present invention.
Figure 9 is a diagram showing an atomic force microscope (AFM) analysis image of the NiO and NiO:BN hole transport layer thin films according to an embodiment of the present invention.
Figure 10 is a diagram showing an X-ray diffraction (XRD) pattern for a perovskite photoactive layer formed on a thin film of NiO and NiO:BN hole transport layer according to an embodiment of the present invention.
Figure 11 shows a scanning electron microscope (SEM) image of the perovskite photoactive layer formed on the NiO and NiO:BN hole transport layer thin film according to an embodiment of the present invention and the NiO and NiO:BN hole transport layer thin film This is a diagram showing the grain size distribution of the perovskite formed above.
Figure 12 is a diagram showing the water contact angle of NiO and NiO:BN hole transport layer thin films according to an embodiment of the present invention.
Figure 13 shows series and parallel resistance changes, open circuit voltage changes according to light intensity, and photoluminescence (PL) of perovskite solar cells containing NiO and NiO:BN hole transport layers according to an embodiment of the present invention. ) This is a diagram showing the characteristics, photo-CELIV (charge extraction by linearly increasing voltage) measurement curve, and photoelectric voltage and photoelectric current reduction time measurement curve.
Figure 14 is a diagram showing the stability in air over time of a perovskite solar cell including NiO and NiO:BN hole transport layers according to an embodiment of the present invention.

Below, with reference to the attached drawings, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts that are not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

In the drawing, the thickness is enlarged to clearly express various layers and areas. Throughout the specification, similar parts are given the same reference numerals. When a part of a layer, membrane, region, plate, etc. is said to be "on" another part, this includes not only being "directly on top" of the other part, but also parts in between. Conversely, when a part is said to be “right on top” of another part, it means that there is no other part in between. Also, when a part is said to be formed “wholly” on top of another part, it means not only that it is formed on the entire surface (or front) of the other part, but also that some of the edges are not formed.

Hereinafter, a high-performance perovskite solar cell using a hole transport layer and a manufacturing method thereof according to an embodiment of the present invention will be described in detail with reference to the attached drawings.

Figure 1 is a schematic diagram of a perovskite solar cell 100 according to an embodiment of the present invention. Referring to FIG. 1, the perovskite solar cell 100 includes a first electrode 110, a hole transport layer 120 formed on the top surface of the first electrode 110, and a top surface of the hole transport layer 120. It may be configured to include a photoactive layer 130 formed on the photoactive layer 130, an electron transport layer 140 formed on the top surface of the photoactive layer 130, and a second electrode 150 formed on the top surface of the electron transport layer 140. there is.

The perovskite solar cell 100 may further include a substrate on the first electrode 110 in a direction opposite to the hole transport layer 120, and the substrate may be a conductive transparent substrate or plastic. It may be a description. For example, any one of plastics including glass substrate, PET (polyethylene terephthalate), PEN (polyethylenenaphthelate), PP (polypropylene), PI (polyamide), TAC (tri acetyl cellulose), PES (polyethersulfone), etc. A flexible substrate containing any one of a plastic substrate containing, aluminum foil, and stainless steel foil may be used.

The first electrode 110 may be a transparent electrode made of a transparent conductive oxide layer. For example, fluorine tin oxide (FTO), indium tin oxide (ITO), ZnO-Ga ₂ O ₃ , ZnO-Al ₂ O ₃ , tin-based oxide, zinc oxide, etc. may be used.

The hole transport layer 120 includes nanoparticles with a NiOx chemical composition, and the NiOx hole transport layer forms a dense thin film along the surface of the first electrode without separation at the interface, thereby reducing the resistance between the two layers. In addition, the hole transport layer 120 can form a NiO:BN complex containing boron nitride, and NiO:BN containing boron nitride improves charge collection efficiency by more effectively extracting and moving holes from the perovskite layer. It can increase the charge and suppress recombination of charges.

The content of boron nitride in the NiO:BN is preferably 1 vol% to 5 vol% (vol: volume), and most preferably approximately 2 vol%.

The photoactive layer 130 is mainly made of perovskite. To form a photoactive layer, a perovskite structure compound may be included, and the perovskite structure compound includes CH ₃ NH ₃ PbI _3-x Cl _x (0≤x≤ 3 real numbers), CH ₃ NH ₃ PbI _3-x Br _x (real numbers with 0≤x≤3), CH ₃ NH ₃ PbCl _3-x Br _x (real numbers with 0≤x≤3), CH ₃ NH ₃ PbI _3-x F _x (real number with 0≤x≤3), Cs _1-xy FA _x MA _y Pb(I _1-z Br _z ) ₃ (0≤x≤1, 0≤y≤1, 0≤1- real numbers (xy≤1, 0≤z≤1), etc. are possible. In this case, Cs is Cesium, FA is Formamidinium, MA is Methylammonium, Pb is lead, I is Iodide, and Br is Bromide. This means that a perovskite light absorption layer with a composition of Cs _0.175 FA _0.750 MA _0.075 Pb(I _0.880 Br _0.120 ) ₃ may be most preferable.

At this time, the weight percent concentration of the perovskite precursor solvent is the starting materials formamidinium iodide (FAI), methylammonium bromide (MABr), and cesium iodide (CsI), bromide. A mixed solute of Lead Bromide (PbBr ₂ ) and Lead Iodide (PbI ₂ ) in a ratio of Cs _0.175 FA _0.750 MA _0.075 Pb (I _0.880 Br _0.120 ) ₃ and dimethylformamide (DMF). : Calculated through the relationship [Weight of solute/(Weight of solute + Weight of solution)

Perovskite precursor solvents include polar solvents including N,N-Dimethylformamide (DMF), G-butyrolactone (GBL), N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO), and N,N-dimethylacetamide (DMAc). Mixed solvents, etc. may be used.

The electron transport layer 140 may include a fullerene derivative (C60) and a metal oxide layer, and the metal oxide layer is SnO ₂ , ZnO, MgO, WO ₃ , PbO, In2O ₃ , Bi2O ₃ , Ta ₂ O ₅ , BaTiO ₃ , BaZrO ₃ , ZrO ₃ , etc. The electron transport layer 140 may be composed of a first electron transport layer (not shown) and a second electron transport layer (not shown). The first electron transport layer (not shown) is made of PCBM ([6,6]-phenyl-C61-butyric acid methyl ester (PC61BM), and the second electron The transport layer may be ZnO _x or the like.

The second electrode 150 may be made of Ag, Au, Pt, Ni, Cu, In, Ru, Pd, Rh, Ir, Os, C, conductive polymer, etc., and is preferably Ag.

Although FIG. 1 shows a solar cell with an inverted structure, it is not limited thereto, and an embodiment of the present invention can also be applied to a positive structure. That is, the electron transport layer may be formed on the upper surface of the lower transparent electrode, and the hole transport layer may be formed on the upper surface of the photoactive layer.

Figure 2 is a process chart showing the process of preparing a dispersion according to an embodiment of the present invention. Referring to Figure 2, first prepare boron nitride powder and IPA (IsoPropyl Alcohol) solution (step S210).

Add 0.5 mg of boron nitride powder to 1 ml of IPA solution and sonicate for about 3 to 4 hours to prepare a boron nitride dispersion (step S220).

Thereafter, 1 vol% to 5 vol% of the boron nitride dispersion is added to the _NiO NiOx dispersion is a mixture of 2.5 wt% NiO _x in IPA solution.

Figure 3 is a process chart showing the process of perovskite solar cell using the dispersion prepared in Figure 2. Referring to FIG. 3, the indium tin oxide (ITO) substrate, which becomes the first electrode 110, is washed in an ultrasonic machine for 20 minutes in the order of acetone, distilled water, and isopropyl alcohol, and then placed in an oven at 80° C. for 10 minutes. It was dried. Afterwards, the substrate was treated with ultraviolet rays and ozone for 30 minutes to improve wettability and remove impurities (step S310).

The NiO:BN dispersion was coated on the upper surface of the first electrode 110 prepared as above at 3500 to 4500 rpm (revolutions per minute) (preferably 4000 rpm) for 35 to 45 seconds (preferably 40 seconds) to form a hole transport layer. (120) was generated (step S320). At this time, coating was performed at room temperature, and heat treatment was performed at about 300 to 350°C (preferably 300°C) for about 25 to 35 minutes (preferably 30 minutes). The coating method is spin coating, but is not limited to this, and spray coating, slot die coating, bar coating, doctor blade, etc. may be used.

Then, in order to form the photoactive layer 130 on the upper surface of the hole transport layer 120, first formamidinium iodide (FAI), methylammonium bromide (MABr), and cesium iodide (Cesium iodide) Iodide, CsI), Lead Bromide (PbBr ₂ ), and Lead Iodide (PbI ₂ ) are mixed with dimethylformamide (DMF) in the ratio of Cs _0.175 FA _0.750 MA _0.075 Pb(I _0.880 Br _0.120 ) ₃ ): A perovskite precursor solution was prepared by dissolving in a mixed solution of dimethyl sulfoxide (DMSO) = 8:2.

To elaborate, Formaminium Iodide (FAI), Methylammonium Bromide (MABr), Cesium Iodide (CsI), Lead Bromide (PbBr ₂ ), Lead Iodide (Lead Iodide) , PbI ₂ ), and perovskite tuning based on them is all possible.

The perovskite precursor solution was first coated on the hole transport layer 120 of NiO:BN at 450 to 550 rpm (preferably 500 rpm) for 4 to 6 seconds (preferably 5 seconds), and then coated at 4500 to 5500 rpm (preferably 5 seconds). A secondary coating was performed at 5000 rpm for 40 to 50 seconds (preferably 45 seconds), and chlorobenzene (CB) was sprayed 25 to 35 seconds (preferably 30 seconds) before the end of coating. Next, heat treatment was performed at 95 to 105°C (preferably 100°C) for 25 to 35 minutes (preferably 30 minutes) to form a photoactive layer 130 having a perovskite structure (steps S330 and S340).

Thereafter, [6,6]-phenyl dispersed at 20 mg/ml in 1,2-dichlorobenzene (CB) to form a first electron transport layer on the upper surface of the photoactive layer 130. -C61-butyric acid methyl ester ([6,6]-phenyl-C61-butyric acid methyl ester, PC61BM=PCBM) at 5500 to 6500 rpm (preferably 6000 rpm) for 45 to 55 seconds (preferably 50 seconds) Spin coating was performed, and then heat treatment was performed at 95 to 105°C (preferably 100°C) for 9 to 11 minutes (preferably 10 minutes). The ZnOx nanoparticle dispersion, which is the second electron transport layer, was spin-coated at 7500 to 8500 rpm (preferably 8000 rpm) for 35 to 45 seconds (preferably 40 seconds) (steps S350 and S360).

Finally, using a thermal evaporator, the silver (Ag) of the second electrode 150 has a thickness of 95 to 105 nm (preferably 100 nm) and an effective thickness of 4.00 to 5.00 mm ² (preferably 4.64 mm ^{2 )} . It was deposited at a speed of 0.5 to 1.5 Å/s (preferably 1.0 Å/s) to have an area (step S370).

<Example 1>

The manufacturing _process of the _NiO

(1) 0.5 mg of boron nitride powder was added to 1 ml of IPA solution and sonicated for 3 to 4 hours to prepare a boron nitride dispersion.

(2) 1 vol% to 5 vol% of the boron nitride dispersion was added to the NiO _x (2.5 wt% NiO _x in IPA) dispersion and stirred for 24 hours to finally prepare a NiO:BN dispersion.

<Comparative Example 1>

As a comparative example of the present invention, the pure _NiO

<Example 2>

The perovskite solar cell of the present invention includes a first electrode (110); A hole transport layer 120 formed on the upper surface of the first electrode 110; A perovskite photoactive layer 130 formed on the upper surface of the hole transport layer 120; An electron transport layer 140 formed on the upper surface of the perovskite photoactive layer 130; It may include a second electrode 150 formed on the upper surface of the electron transport layer 140.

The first electrode 110 may be made of fluorine tin oxide (FTO), indium tin oxide (ITO), ZnO-Ga ₂ O ₃ , ZnO-Al ₂ O ₃ , tin-based oxide, zinc oxide, etc. The hole transport layer 120 contains nanoparticles of NiOx chemical composition, and the NiOx hole transport layer forms a dense thin film along the surface of the first electrode 110 without separation at the interface, thereby reducing the resistance between the two layers. .

In addition, the hole transport layer 120 can form a NiO:BN complex containing boron nitride, and NiO:BN containing boron nitride extracts and moves holes from the perovskite layer more effectively, thereby increasing the charge collection efficiency. can increase and suppress recombination of charges. The content of boron nitride in the NiO:BN is preferably 1 vol% to 5 vol%, and most preferably approximately 2 vol%.

The perovskite photoactive layer 130 may include a compound with a perovskite structure, and the compound with the perovskite structure is CH ₃ NH ₃ PbI _3-x Cl _x ( real number with 0≤x≤3), CH ₃ NH ₃ PbI _3-x Br _x (real number with 0≤x≤3), CH ₃ NH ₃ PbCl _3-x Br _x (real number with 0≤x≤3), CH ₃ NH ₃ PbI _3-x F _x (real number with 0≤x≤3), Cs _1-xy FA _x MA _y Pb(I _1-z Br _z ) ₃ (0≤x≤1, 0≤y≤1, Real numbers such as 0≤1-xy≤1, 0≤z≤1) are possible. In this case, Cs stands for Cesium, FA stands for Formamidinium, MA stands for Methylammonium, Pb stands for lead, I stands for Iodide, and Br stands for Bromide, and the perovskite has a composition of Cs _0.175 FA _0.750 MA _0.075 Pb (I _0.880 Br _0.120 ) ₃ . A light absorbing layer may be most desirable.

The weight percent concentration of the perovskite precursor solvent is preferably between 20 wt% and 56 wt%, and most preferably approximately 48 wt%.

<Comparative Example 2>

A perovskite solar cell was prepared in the same manner as Example 2, except that pure NiO _x dispersion prepared according to Comparative Example 1 was used instead of the NiO:BN dispersion prepared according to Example 1.

The electron transport layer 140 may include a fullerene derivative (C60) and a metal oxide layer, and the metal oxide layer is SnO ₂ , ZnO, MgO, WO ₃ , PbO, In2O ₃ , Bi2O ₃ , Ta ₂ O ₅ , BaTiO ₃ , BaZrO ₃ , ZrO ₃ , etc.

The second electrode 150 may be Ag, Au, Pt, Ni, Cu, In, Ru, Pd, Rh, Ir, Os, C, conductive polymer, etc., and preferably Ag.

Figure 4 is a diagram showing an energy-dispersive X-ray spectroscopy (EDS) element mapping image for a NiO:BN hole transport layer thin film according to an embodiment of the present invention. Referring to FIG. 4, it can be seen that NiO nanoparticles (210,220) and boron nitride nanoparticles (230,240) are uniformly distributed in the NiO:BN hole transport layer manufactured according to the invention.

Figure 5 is a diagram showing high-resolution X-ray photoelectron spectroscopy (XPS) of a NiO:BN hole transport layer thin film according to an embodiment of the present invention. Referring to Figure 5, Ni2p _3/2 and O1s characteristic peaks were observed simultaneously in the NiO and NiO:BN thin films, and it was confirmed that each peak was located at the same position. On the other hand, B1s and N1s characteristic peaks were observed only in NiO:BN thin films. From this, it can be seen that there is no chemical reaction between NiO and BN and that BN exists only in the NiO:BN thin film.

In Figure 5, "satellite" is a satellite peak that appears around the main peak, and when some of the component elements are oxidized (or reduced), the main peak of the component elements and a satellite peak due to oxidation (or reduction) appear.

“CPS (counts per second)” refers to the number of signals entering the spectrum detector. The higher the frequency of the signal, the higher the cps appears and the stronger the intensity of the peak in the spectrum.

Figure 6 is a diagram showing the current-voltage curve and statistics of photoelectric conversion efficiency (PCE) of a perovskite solar cell having a NiO or NiO:BN thin film as a hole transport layer according to an embodiment of the present invention. . That is, Figure 6(a) shows the current density-voltage curve, and Figure 6(b) shows the photoelectric conversion efficiency (PCE)-BN content relationship. Referring to Figure 6, the performance of the perovskite solar cell improved when the NiO:BN hole transport layer was introduced, and the NiO:BN hole transport layer containing 2 vol% of boron nitride showed the best photoelectric conversion efficiency. . From this, it can be seen that NiO:BN containing 2 vol% of boron nitride is most preferable. To make this easier to understand, this can be expressed in a table as follows. That is, Table 1 shows detailed performance data of the perovskite solar cell with a NiO:BN hole transport layer containing NiO and 2 vol%BN shown in FIG. 6.

Here, HTL is the Hole Transporting Layer, Voc is the open-circuit voltage, Jsc is the short-circuit current density, and FF is the Fill Factor.

Figure 7 shows the steady-state photocurrent output, external quantum efficiency (EQE), and external quantum efficiency (EQE) at the maximum power point voltage of a perovskite solar cell having a NiO or NiO:BN thin film as a hole transport layer according to an embodiment of the present invention. This is a diagram showing the internal quantum efficiency (IQE). That is, Figure 7(a) is the current density-time relationship, Figure 7(b) is the external quantum efficiency (EQE)-wavelength curve, and Figure 7(c) is the internal quantum efficiency-wavelength curve.

Referring to Figure 7, perovskite solar cells with NiO:BN hole transport layer were shown to have higher steady-state photocurrent output at the maximum power point voltage. In addition, the external quantum efficiency (EQE) spectrum of the perovskite solar cell with a NiO:BN hole transport layer containing boron nitride was found to be improved at all wavelengths compared to the NiO hole transport layer without boron nitride. This indicates that the NiO:BN hole transport layer can provide better light harvesting performance.

Continuing to refer to FIG. 7, the perovskite solar cell with the NiO:BN hole transport layer also showed a high value in the internal quantum efficiency (IQE) spectrum, and considering that the degree of improvement was similar, the NiO:BN hole transport layer showed a high value. It can be seen that the efficiency improvement resulting from the introduction is mainly due to the improvement of charge extraction and transfer characteristics.

FIG. 8 is a diagram showing an ultraviolet spectral spectrum of a NiO and NiO:BN hole transport layer thin film and an energy band diagram of a perovskite solar cell including a NiO and NiO:BN hole transport layer according to an embodiment of the present invention. That is, Figure 8(a) is a graph between intensity and binding energy, and Figure 8(b) is an energy band diagram. Referring to FIG. 8, the electron transport layer 140 is composed of a first electron transport layer 841 and a second electron transport layer 842.

As shown in (a) of Figure 8, the work function of the NiO:BN hole transport layer was 4.9 eV, which was higher than the 4.6 eV of the NiO hole transport layer, and the valence band energy level was 0.3 eV lower than that of the NiO hole transport layer. It was found to have ~5.7 eV.

From this, as shown in (b) of Figure 6, it can be seen that the energy level of the NiO:BN hole transport layer matches well with the perovskite, which means that the NiO:BN hole transport layer facilitates the movement of holes. This means that it is more suitable for improving the efficiency of solar cells.

Figure 9 is a diagram showing an atomic force microscope (AFM) analysis image of the NiO and NiO:BN hole transport layer thin films according to an embodiment of the present invention. Referring to FIG. 9, non-uniform film surface or non-homogeneous film shape may cause charge recombination, high resistance, reduced hole extraction, etc., thereby lowering the filling factor and ultimately acting as a factor in reducing device performance.

As shown in Figure 9, the surface roughness (root-means-square roughness; rms) of the NiO and NiO:BN hole transport layer thin films were measured to be ~3.42nm and ~2.40nm, respectively, and as a result, the NiO:BN hole transport layer It can be seen that the performance of perovskite solar cells can be superior.

Figure 10 is a diagram showing an X-ray diffraction (XRD) pattern for a perovskite photoactive layer formed on a thin film of NiO and NiO:BN hole transport layer according to an embodiment of the present invention. Referring to FIG. 10, it can be seen that the perovskite formed for the NiO:BN hole transport layer prepared according to an embodiment of the present invention and the perovskite formed on the conventional NiO hole transport layer have the same characteristic diffraction peak. there is.

Through this, it can be confirmed that there is no effect on the perovskite crystal structure when the NiO:BN hole transport layer is introduced. On the other hand, the full width at half maximum (FWHM) of NiO:BN (~0.252) was smaller than that of NiO (~0.269), and the crystallinity of the perovskite formed on the NiO:BN hole transport layer was superior. can be seen.

11 is a scanning electron microscope (SEM) image of a perovskite photoactive layer formed on a NiO and NiO:BN hole transport layer thin film according to an embodiment of the present invention and a scanning electron microscope (SEM) image of the perovskite photoactive layer formed on the NiO and NiO:BN hole transport layer thin film according to an embodiment of the present invention. This is a diagram showing the grain size distribution of the formed perovskite. That is, Figure 11 (a) is a scanning electron microscope (SEM) image of a perovskite photoactive layer formed on a NiO hole transport layer thin film, and Figure 11 (b) is a perovskite photoactive layer formed on a NiO:BN hole transport layer thin film. This is a scanning electron microscope (SEM) image of the photoactive layer, and Figure 11 (c) is a diagram showing the grain size distribution of perovskite formed on the NiO and NiO:BN hole transport layer thin films.

Referring to Figure 11, there appeared to be some differences in the particle size distribution and formation of the perovskite thin films formed on the NiO and NiO:BN hole transport layers. While the perovskite thin film formed on the NiO hole transport layer had a small particle size, the particle size of the perovskite thin film formed on the NiO:BN hole transport layer increased by 12.5%.

Figure 12 is a diagram showing the water contact angle of NiO and NiO:BN hole transport layer thin films according to an embodiment of the present invention. Referring to FIG. 12, it can be seen that the water contact angle 1120 of the NiO:BN hole transport layer is about 10° smaller than the water contact angle 110 of the NiO hole transport layer. Therefore, it can be seen that the change in grain size of the perovskite thin film may be due to the change in the water contact angle of the NiO hole transport layer due to the addition of boron nitride.

Figure 13 shows series and parallel resistance changes, open circuit voltage changes according to light intensity, and photoluminescence (PL) of perovskite solar cells containing NiO and NiO:BN hole transport layers according to an embodiment of the present invention. ) This is a diagram showing the characteristics, photo-CELIV (charge extraction by linearly increasing voltage) measurement curve, and photoelectric voltage and photoelectric current reduction time measurement curve. That is, in Figure 13 (a) is the series (R _s ) and parallel (R _sh ) resistance change, (b) is the open circuit voltage change according to the intensity of light, (c) is the photoluminescence (PL) characteristics, (d) shows the photo-CELIV measurement curve, (e) shows the photoelectric current reduction time measurement curve, and (f) shows the photoelectric voltage reduction time measurement curve.

Referring to FIG. 13, in (a) of FIG. 13, the series (R _s ) and parallel (R _sh ) resistances were calculated as 1/slope at the open circuit voltage and short circuit current points of the current-voltage curve. To elaborate, the series resistance was calculated by taking the reciprocal of the slope (1/slope) at the point where the current density of the JV curve is 0 in Figure 6 (a). In addition, the parallel resistance was calculated by taking the reciprocal of the slope (1/slope) at the point where the current density of the JV curve is maximum and the voltage is 0 in Figure 6 (a).

When NiO:BN was introduced as the hole transport layer, it was observed that the average R _s of the solar cell decreased from ~ 2.5 to ~ 1.9 Ω cm ² and the average R _sh of the solar cell increased from ~ 4599 to ~ 7192 Ω cm ² . Therefore, it is believed that using NiO:BN as a hole transport layer reduces the interfacial resistance and leakage current, and improves FF and V _OC in NiO:BN-based perovskite solar cells.

The closer the open circuit voltage change value according to the light intensity shown in (b) of FIG. 13 is to 1, the more suppressed the trap-assisted recombination is. The open circuit voltage change value according to the light intensity of the perovskite solar cell with a NiO hole transport layer is 1.26 kT/q, but the perovskite solar cell with a NiO:BN hole transport layer decreases to 1.18 kT/q. It can be seen that charge recombination due to the trap is effectively suppressed.

This indicates that traps present at the interface between the NiO:BN hole transport layer and the perovskite photoactive layer or within the hole transport layer were effectively suppressed. As a result, charge recombination due to the trap was reduced, thereby improving Voc.

In (c) of FIG. 13, the photoluminescence intensity of the perovskite thin film formed on the NiO:BN hole transport layer was smaller than the photoluminescence intensity of the perovskite thin film formed on the NiO:BN hole transport layer. This means that charge recombination is suppressed by introducing a hole transport layer, and as a result, the Jsc and Voc of the solar cell can be improved.

In addition, (d) of FIG. 13 shows the mobility of the light-generated charge carrier, and the perovskite solar cell with a NiO:BN hole transport layer has a higher charge mobility than the perovskite solar cell with a NiO hole transport layer. indicate This increase in mobility indicates a decrease in recombination, and from this, it can be seen that charge recombination by traps in the perovskite solar cell was reduced with the introduction of the NiO:BN hole transport layer.

In addition, (e) and (f) of FIG. 13 show the photoelectric current and photovoltage reduction time measurement curves, and the photovoltage and photocurrent reduction time are related to the life of the charge carrier and charge extraction and transfer characteristics in an actually operating solar cell. represents. The photovoltage value of perovskite solar cells with a NiO:BN hole transport layer increased, indicating that the charge recombination lifetime increased, and since the charge recombination lifetime is inversely proportional to charge recombination, the solar cell was increased by introducing a NiO:BN hole transport layer. It can be seen that charge recombination is effectively suppressed.

In contrast, the photocurrent value of the perovskite solar cell with the NiO:BN hole transport layer decreased, indicating that the charge extraction and transfer characteristics were improved with the introduction of the NiO:BN hole transport layer.

As a result, it can be seen that the introduction of the NiO:BN hole transport layer improves the charge recombination lifetime and charge extraction and transfer characteristics, and the resulting improvements in Voc, Jsc, and FF enable the perovskite solar cell with NiO:BN as the hole transport layer. It can be seen that the performance has been improved.

Figure 14 is a diagram showing the stability in air over time of a perovskite solar cell including NiO and NiO:BN hole transport layers according to an embodiment of the present invention. Referring to FIG. 14, the efficiency of the perovskite solar cell with a conventional NiO hole transport layer after 60 days at 25°C and 30 to 60% air condition was maintained at ~57% compared to the initial efficiency, but NiO: The efficiency of the perovskite solar cell with a BN hole transport layer was maintained at ~85% compared to the initial level. The above results indicate that perovskite solar cells with a NiO:BN hole transport layer have better stability in air.

100: High-performance perovskite solar cell
110: first electrode
120: hole transport layer
130: Photoactive layer
140: electron transport layer
150: second electrode

Claims (1)

In high-performance perovskite solar cells,
first electrode 110;
A hole transport layer 120 formed on the upper surface of the first electrode 110;
A photoactive layer 130 formed on the upper surface of the hole transport layer 120 and containing a perovskite structure compound;
an electron transport layer 140 formed on the upper surface of the photoactive layer 130; and
It includes a second electrode 150 formed on the upper surface of the electron transport layer 140,
The hole transport layer 120 is formed by coating the upper surface of the first electrode 110 with a dispersion liquid,
In order to lower the interfacial resistance between the photoactive layer 130 and the hole transport layer 120 and to reduce recombination of photo-generated charges by traps, the dispersion is a NiO:BN dispersion,
The NiO:BN dispersion is produced by adding 1 vol% to 5 vol% of boron nitride dispersion to the NiOx dispersion and stirring for 23 to 25 hours,
The NiOx dispersion is produced by placing boron nitride powder in an isopropyl alcohol solution and sonicating it for 3 to 4 hours.
The above compounds of perovskite structure are CH ₃ NH ₃ PbI _3-x Cl _x (real number with 0≤x≤3), CH ₃ NH ₃ PbI _3-x Br _x (real number with 0≤x≤3), CH ₃ NH ₃ PbCl _3-x Br _x (real number 0≤x≤3), CH ₃ NH ₃ PbI _3-x F _x (real number 0≤x≤3), and Cs _1-xy FA _x MA _y Pb( I _1-z Br _z ) ₃ (real number 0≤x≤1, 0≤y≤1, 0≤1-xy≤1, 0≤z≤1) (where Cs is cesium and FA is form A hole characterized in that it is one of amidinium (formamidinium), MA means methylammonium (Methylammonium), Pb means lead, I means Iodide (Iodide), Br means bromide) High-performance perovskite solar cell using a transport layer.