CONDUCTIVE SUBSTRATE, PEROVSKITE SUBSTRATE USING THE CONDUCTIVE SUBSTRATE AND SOLAR CELL USING THE PEROVSKITE SUBSTRATE

Abstract

The present invention discloses a conductive substrate, a perovskite substrate using the conductive substrate, and a solar cell using the perovskite substrate. The conductive substrate, the perovskite substrate, and the solar cell of the present invention include a conductive base and a conductive compound stacked on the conductive base. The conductive compound is represented by Formula 1, 2 or 3. The conductive compound is capable of multi-electron redox reactions, possesses p-type organic molecular properties, and has an oxidation potential or highest occupied molecular orbital (HOMO) matching the valence band of perovskite so that holes generated in an absorber layer are selectively separated for the application of the perovskite material, achieving enhanced photoelectric conversion efficiency of the solar cell and a significantly reduced difference between the forward and reverse conversion efficiencies (hysteresis index) of the solar cell.

Claims

1. A conductive substrate comprising a conductive base and a conductive compound stacked on the conductive base, the conductive compound being represented by Formula 1, 2 or 3: ##STR00022## wherein Z is S, O or N, R is CH2.sub.n (n=1-10), ##STR00023## (n=1-4), R1 and R2 are each independently H, F, Cl, Br, I, CN, NO.sub.2, alkyl chain, OCH.sub.3, NH.sub.2, N(alkyl).sub.2, N(aromatic).sub.2, OCH2CH2.sub.n (n=1-10), ##STR00024## (X=H, F, Cl, Br, I, CN, NO.sub.2, alkyl chain, OCH.sub.3, NH.sub.2 or N(alkyl).sub.2), and R3 is CH2.sub.n (n=1-10), OCH2CH2.sub.n (n=1-10), ##STR00025## (Y=F, Cl, Br, I, CN, NO.sub.2, alkyl chain, OCH.sub.3, NH.sub.2, N(alkyl).sub.2 or ##STR00026## (n=1-4), ##STR00027##

2. The conductive substrate according to claim 1, further comprising a current carrying layer deposited between the conductive base and the conductive compound.

3. The conductive substrate according to claim 1, wherein the conductive compound forms a self-assembled monolayer (SAM).

4. The conductive substrate according to claim 1, wherein the conductive compound is a hole transport material.

5. The conductive substrate according to claim 1, wherein the conductive compound has a dipole moment of 0.1 to 6.

6. A perovskite substrate comprising the conductive substrate according to claim 1 and a perovskite layer stacked on the conductive substrate.

7. A solar cell comprising the perovskite substrate according to claim 6.

8. A method for preparing the conductive substrate according to claim 1 comprising the conductive compound represented by Formula 2 stacked on the conductive base, the method comprising sequentially synthesizing 10-(2-bromoethyl)-10H-phenothiazine, 3,7-dibromo-10-(2-bromoethyl)-10H-phenothiazine, diethyl(2-(3,7-dibromo-10H-phenothiazin-10-yl)ethyl)phosphonate, and (2-(3,7-dibromo-10H-phenothiazin-10-yl)ethyl)phosphonic acid.

9. The method according to claim 8, wherein the 10-(2-bromoethyl)-10H-phenothiazine is synthesized by reacting phenothiazine with 1,2-chloroethanol and brominating the terminal hydroxyl group of the reaction product.

10. A method for preparing the conductive substrate according to claim 1 comprising the conductive compound represented by Formula 3, the method comprising sequentially synthesizing 10-(2-bromoethyl)-10H-phenothiazine, 3,7-dibromo-10-(2-bromoethyl)-10H-phenothiazine, diethyl(2-(3,7-dibromo-10H-phenothiazin-10-yl)ethyl)phosphonate, and (2-(3,7-dibromo-10H-phenothiazin-10-yl)ethyl)phosphonic acid.

11. The method according to claim 10, wherein the 10-(2-bromoethyl)-10H-phenothiazine is synthesized by reacting phenothiazine with 1,2-chloroethanol and brominating the terminal hydroxyl group of the reaction product.

12. A conductive compound represented by Formula 1, 2 or 3: ##STR00028## wherein Z is S, O or N, R is CH2.sub.n (n=1-10), ##STR00029## (n=1-4), R1 and R2 are each independently H, F, Cl, Br, I, CN, NO.sub.2, alkyl chain, OCH.sub.3, NH.sub.2, N(alkyl).sub.2, N(aromatic).sub.2, OCH2CH2.sub.n (n=1-10), ##STR00030## (X=H, F, Cl, Br, I, CN, NO.sub.2, alkyl chain, OCH.sub.3, NH.sub.2 or N(alkyl).sub.2), and R3 is CH2.sub.n (n=1-10), OCH2CH2.sub.n (n=1-10), ##STR00031## (Y=F, Cl, Br, I, CN, NO.sub.2, alkyl chain, OCH.sub.3, NH.sub.2, N(alkyl).sub.2 or ##STR00032## (n=1-4), ##STR00033##

13. The conductive compound according to claim 12, wherein the conductive compound forms a self-assembled monolayer (SAM).

14. The conductive compound according to claim 12, wherein the conductive compound is a hole transport material.

15. The conductive compound according to claim 12, wherein the conductive compound has a dipole moment of 0.1 to 6.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is a perspective view of a conductive substrate according to the present invention,

[0030] FIG. 2 is a perspective view of a solar cell using a perovskite substrate of the present invention,

[0031] FIG. 3 is a .sup.1H NMR spectrum of Compound 1-1 according to the present invention,

[0032] FIG. 4 is a .sup.1H-.sup.1H COZY NMR spectrum of Compound 1-1 according to the present invention,

[0033] FIG. 5 is a .sup.1H NMR spectrum of Compound 1-2 according to the present invention,

[0034] FIG. 6 is a .sup.1H-.sup.1H COZY NMR spectrum of Compound 1-2 according to the present invention,

[0035] FIG. 7 is a .sup.1H NMR spectrum of Compound 1-3 according to the present invention,

[0036] FIG. 8 is a .sup.1H-.sup.1H COZY NMR spectrum of Compound 1-3 according to the present invention,

[0037] FIG. 9 is a .sup.1H NMR spectrum of Compound 2-2 according to the present invention,

[0038] FIG. 10 is a .sup.1H-.sup.1H COZY NMR spectrum of Compound 2-2 according to the present invention,

[0039] FIG. 11 is a .sup.1H NMR spectrum of Compound 2-3 according to the present invention,

[0040] FIG. 12 is a .sup.1H-.sup.1H COZY NMR spectrum of Compound 2-3 according to the present invention, FIG. 13 is a .sup.1H NMR spectrum of Compound 2-4 according to the present invention,

[0041] FIG. 14 is a .sup.1H-.sup.1H COZY NMR spectrum of Compound 2-4 according to the present invention,

[0042] FIG. 15 shows cyclic voltammograms of compounds prepared in Preparative Examples 1-2 and Comparative Examples 1-2.

BEST MODE FOR CARRYING OUT THE INVENTION

[0043] The present invention will now be described in detail.

[0044] Technical terms used in this specification are used to merely illustrate specific embodiments, and should be understood that they are not intended to limit the present invention. As far as not being defined differently, technical terms used herein may have the same meaning as those generally understood by an ordinary person skilled in the art to which the present invention belongs, and should not be construed in an excessively comprehensive meaning or an excessively restricted meaning.

[0045] In addition, if a technical term used in the description of the present invention is an erroneous term that fails to clearly express the idea of the present invention, it should be replaced by a technical term that can be properly understood by the skilled person in the art. In addition, general terms used in the description of the present invention should be construed according to definitions in dictionaries or according to its front or rear context.

[0046] As used herein, the singular forms a, an and the are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms comprises, comprising, includes and/or including as used herein should not be construed to necessarily include all of the elements or steps disclosed herein, and should be construed not to include some of the elements or steps thereof, or should be construed to further include additional elements or steps. In the description of the present invention, detailed explanations of related art are omitted when it is deemed that they may unnecessarily obscure the essence of the invention.

[0047] FIG. 1 is a perspective view of a conductive substrate according to the present invention, FIG. 2 is a perspective view of a solar cell using a perovskite substrate of the present invention, FIG. 3 is a .sup.1H NMR spectrum of Compound 1-1 according to the present invention, FIG. 4 is a .sup.1H-.sup.1H COZY NMR spectrum of Compound 1-1 according to the present invention, FIG. 5 is a .sup.1H NMR spectrum of Compound 1-2 according to the present invention, FIG. 6 is a .sup.1H-.sup.1H COZY NMR spectrum of Compound 1-2 according to the present invention, FIG. 7 is a .sup.1H NMR spectrum of Compound 1-3 according to the present invention, FIG. 8 is a .sup.1H-.sup.1H COZY NMR spectrum of Compound 1-3 according to the present invention, FIG. 9 is a .sup.1H NMR spectrum of Compound 2-2 according to the present invention, FIG. 10 is a .sup.1H-.sup.1H COZY NMR spectrum of Compound 2-2 according to the present invention, FIG. 11 is a .sup.1H NMR spectrum of Compound 2-3 according to the present invention, FIG. 12 is a .sup.1H-.sup.1H COZY NMR spectrum of Compound 2-3 according to the present invention, FIG. 13 is a .sup.1H NMR spectrum of Compound 2-4 according to the present invention, FIG. 14 is a .sup.1H-.sup.1H COZY NMR spectrum of Compound 2-4 according to the present invention, and FIG. 15 shows cyclic voltammograms of compounds prepared in Preparative Examples 1-2 and Comparative Examples 1-2. The present invention will be described with reference to the FIGS. 1-15.

[0048] The conductive substrate of the present invention includes a conductive base and a conductive compound stacked on the conductive base, the conductive compound being represented by Formula 1:

##STR00007##

[0049] wherein Z is S, O or N, R is CH2.sub.n (n=1-10),

##STR00008##

(n=1-4), R1 and R2 are each independently H, F, Cl, Br, I, CN, NO.sub.2, alkyl chain, OCH.sub.3, NH.sub.2, N(alkyl).sub.2, N(aromatic).sub.2, OCH2CH2.sub.n (n=1-10),

##STR00009##

(X=H, F, Cl, Br, I, CN, NO.sub.2, alkyl chain, OCH.sub.3, NH.sub.2 or N(alkyl).sub.2), and R3 is CH2.sub.n (n=1-10), OCH2CH2.sub.n (n=1-10),

##STR00010##

(Y=F, Cl, Br, I, CN, NO.sub.2, alkyl chain, OCH.sub.3, NH.sub.2, N(alkyl).sub.2 or

##STR00011##

(n=1-4).

[0050] The conductive substrate of the present invention may further include a current carrying layer 120 deposited between the conductive base 100 and the conductive compound 110.

[0051] As long as the current carrying layer is electrically conductive, any material may be used without particular limitation for the current carrying layer. For example, when the conductive base is made of a glass, plastic or polymeric material because transparency is required, the current carrying layer may be formed by depositing an oxide such as indium tin oxide (ITO) or fluorine-doped tin oxide (FTO) on the conductive base by a physical or chemical vapor deposition process.

[0052] The conductive compound may form a self-assembled monolayer (SAM). The term self-assembled monolayer (SAM) refers to a film of regularly aligned organic molecules that can be stacked and spontaneously coated on the surface of a base. The self-assembled monolayer can be used as a hole transport layer.

[0053] The conductive compound may have a dipole moment of 0.1 to 6. The electric dipole moment is expressed as the product of the distance between a positive charge and a negative charge spaced a distance from each other and the quantity of the electric charges. The difference in energy between the work function of the conductive base and the valence band of a perovskite absorber layer is greater than that required for hole transport. This energy difference acts as a factor that lowers the open circuit voltage of a solar cell to deteriorate the efficiency of the solar cell. Thus, a reduction in the energy difference will improve the efficiency of a solar cell. If the dipole moment is less than 0.1, the effect of the difference in energy between the work function of the conductive base and the valence band of a perovskite absorber layer may be insignificant. Meanwhile, if the dipole moment exceeds 6, the work function of the conductive base may be much lower than the energy of the valence band of a perovskite absorber layer, with the result that efficient hole transport is impeded.

[0054] The conductive compound may be a hole transport material that is in close contact with the current carrying layer. In this case, the conductive compound may be used, for example, in solar cell applications, as well as light emitting devices, X-ray detectors, photodetectors, memories, rectifiers, transistors, thermoelectric elements, and piezoelectric elements, when stacked with a perovskite thin film.

[0055] The present invention also provides a perovskite substrate including the conductive substrate and a perovskite layer 130 stacked on the conductive substrate. The perovskite substrate significantly reduces the difference between the forward and reverse conversion efficiencies (hysteresis index) when a current is applied thereto.

[0056] Due to its hysteresis-controlled electrical properties, the perovskite substrate can be used in a variety of applications. For example, the perovskite substrate may be used in a variety of applications due to its ability to improve the lifetime of a perovskite solar cell, to accurately measure the efficiency of a perovskite solar cell, and to prevent non-radiative recombination to increase the efficiency of a light emitting diode (LED).

[0057] The present invention also provides a solar cell using the perovskite substrate. Based on the significantly reduced difference between forward and reverse conversion efficiencies, the photoelectric conversion efficiency of the solar cell can be greatly enhanced. Hysteresis is caused by various factors, one of which is that electrons and holes generated in the perovskite absorber layer by light are extracted in an electron transport layer and a hole transport layer at different rates, respectively, to produce a capacitor effect at the perovskite absorber layer/electron transport layer interface or the perovskite absorber layer/hole transport layer interface. In the solar cell of the present invention, the charge extraction rates can be increased to significantly reduce the hysteresis effect.

[0058] The solar cell of the present invention can be fabricated by sequentially stacking the conductive compound (SAM) 110 for a hole transport layer, the perovskite layer 130, an electron transport layer (ETL) 140, and a counter electrode 150 on the conductive base (TCO) 100.

[0059] When transparency is required, a current carrying metal oxide material such as ITO or FTO is deposited on the conductive base 100 made of a glass, plastic or polymeric material, as mentioned above, and a hole transport layer is stacked thereon. The perovskite layer 130 stacked on the conductive base 100 is formed of a perovskite material and the electron transport layer 140 is stacked thereon. For electron transfer efficiency and durability, the electron transport layer 140 may be formed by separately stacking fullerene (C60) 142 and BCP 144 on the perovskite layer 130. The counter electrode 150 stacked on the electron transport layer 140 is made of a low resistance material such as silver or gold.

[0060] It should be understood that the electron transport layer may use a material containing fine particles, such as titanium dioxide or tin oxide, to increase its surface area, with the result that the perovskite material can be densely packed over a large area to achieve improved current carrying efficiency.

PREPARATIVE EXAMPLE 1: PREPARATION OF THE COMPOUND OF FORMULA 2

[0061] The SAM compound of Formula 2 was synthetically prepared according to Scheme 1.

##STR00012##

[0062] The chemical names of the compounds shown in Scheme 1 are as follows: 1-1. 10-(2-bromoethyl)-10H-phenothiazine, 1-2. diethyl(2-(10H-phenothiazin-10-yl)ethyl)phosphonate, 1-3. (2-(10H-phenothiazin-10-yl)ethyl)phosphonic acid.

Preparative Example 1-1: Preparation of 10-(2-bromoethyl)-10H-phenothiazine

[0063] Hexane was used for oil removal from a solution of 60% sodium hydride (3.60 g, 90.0 mmol) in oil under argon gas, followed by the addition of N,N-dimethylformamide (20 mL).

[0064] A solution of phenothiazine (6.00 g, 30.1 mmol) in N,N-dimethylformamide (12 mL) was slowly added to the sodium hydride solution. After stirring, the reaction solution was heated to 60? C. and 2-chloroethanol (6.0 mL, 89 mmol) was added thereto. Thereafter, the reaction temperature was again lowered to room temperature, at which stirring was conducted for 5 h. The reaction was quenched with methanol, followed by extraction with ethyl acetate.

[0065] The organic layer was dried over sodium sulfate, the solvent was removed using a rotary evaporator, and the residue and triphenyl phosphine (10.49 g, 39.99 mmol) were dissolved in tetrahydrofuran (40 mL) under argon gas.

[0066] To the resulting solution was added dropwise a solution of carbon tetrabromide (13.27 g, 40.01 mmol) in tetrahydrofuran (15 mL). The mixture was stirred for 3 h. After completion of the reaction, the reaction mixture was evaporated using a rotary evaporator to remove tetrahydrofuran and extracted with methylene chloride.

[0067] The organic layer was dried over sodium sulfate, the solvent was removed using a rotary evaporator, and the residue was purified by column chromatography (eluent: hexane/ethyl acetate 100/0-90/10) to afford Compound 1-1 (4.88 g, 53%).

[0068] .sup.1H NMR (ppm, 400 MHz, CDCl.sub.3) ? 7.18-7.13 (m, 4H), 6.95 (td, J=7.4, 1.2 Hz, 2H), 6.61 (dd, J=8.1, 1.0 Hz, 2H), 4.28 (t, J=7.5 Hz, 2H), 3.63 (t, J=7.8 Hz, 2H).

Structural formula of Compound 1-1

[0069] ##STR00013##

Preparative Example 1-2: Preparation of diethyl(2-(10H-phenothiazin-10-yl)ethyl)phosphonate

[0070] Compound 1-1 (0.31 g, 1.0 mmol) was dissolved in triethyl phosphite (0.86 mL, 5.0 mmol). The solution was stirred under reflux for 18 h.

[0071] After completion of the reaction, the reaction solution was evaporated using a rotary evaporator to remove triethyl phosphite. The residue was purified by column chromatography (eluent: hexane/ethyl acetate 100/0-10/90) to afford Compound 1-2 (0.27 g, 75%).

[0072] .sup.1H NMR (ppm, 400 MHz, CDCl.sub.3) ? 7.18-7.13 (m, 4H), 6.95-6.87 (m, 4H), 4.20-4.09 (m, 6H), 2.34-2.25 (m, 2H), 1.34 (t, J=7.1 Hz, 6H); .sup.13C NMR (ppm, 101 MHz, CDCl.sub.3) ? 144.4, 127.5, 127.4, 125.0, 122.8, 115.1, 61.9 (d, J=6.1 Hz), 41.2, 24.3 (d, J=138.4 Hz), 16.5 (d, J=6.1 Hz); .sup.31P NMR (ppm, 162 MHz, CDCl.sub.3) ? 28.69; HRMS m/z calcd for C.sub.18H.sub.22NO.sub.3PS [M+Na].sup.+386.0950, found 386.0952 (?=0.5 ppm).

##STR00014##

Preparative Example 1-3: Preparation of (2-(10H-phenothiazin-10-yl)ethyl)phosphonic acid

[0073] Compound 1-2 (0.61 g, 1.7 mmol) was dissolved in 1,4-dioxane under argon gas and then bromotrimethylsilane (2.6 mL, 20 mmol) was slowly added thereto. The mixture was stirred for 24 h. After completion of the reaction, the reaction mixture was evaporated using a rotary evaporator to remove the solvent.

[0074] The resulting solid residue was dissolved in methanol. Distilled water was slowly added until the solution became opaque. The mixture was stirred for 15 h. The precipitate was collected by filtration with water to afford Compound 1-3 (0.32 g, 62%).

[0075] .sup.1H NMR (ppm, 400 MHZ, (CD.sub.3).sub.2SO) ? 7.21-7.11 (m, 4H), 6.98-6.91 (m, 4H), 4.04-3.98 (m, 2H), 2.05-1.97 (m, 2H); .sup.13C NMR (ppm, 101 MHZ, (CD.sub.3).sub.2SO) ? 143.9, 127.7, 127.1, 122.9, 122.6, 115.2, 41.8, 25.9 (d, J=131.3 Hz); .sup.31P NMR (ppm, 162 MHZ, (CD.sub.3).sub.2SO) ? 22.37; HRMS m/z calcd for C.sub.14H.sub.16NO.sub.3PS [M+Na].sup.+308.0510, found 308.0506 (A=1.3 ppm).

##STR00015##

PREPARATIVE EXAMPLE 2: PREPARATION OF THE COMPOUND OF FORMULA 3

[0076] The SAM compound of Formula 3 was synthetically prepared according to Scheme 2.

##STR00016## ##STR00017##

[0077] The chemical names of the compounds shown in Scheme 2 are as follows: 2-1. 10-(2-bromoethyl)-10H-phenothiazine, 2-2. 3,7-dibromo-10-(2-bromoethyl)-10H-phenothiazine, 2-3. diethyl(2-(3,7-dibromo-10H-phenothiazin-10-yl)ethyl)phosphonate, 2-4. (2-(3,7-dibromo-10H-phenothiazin-10-yl)ethyl)phosphonic acid

Preparation 2-1: Preparation of 3.7-dibromo-10-(2-bromoethyl)-10H-phenothiazine

[0078] Compound 1-1 (4.58 g, 15.0 mmol) was dissolved in acetic acid (200 ml), followed by stirring. To the reaction solution was slowly added a dilute solution of bromine (2.3 mL, 45 mmol) in acetic acid (50 mL).

[0079] The reaction was quenched with sodium hydrogen sulfite, followed by extraction with ethyl acetate. The organic layer was dried over sodium sulfate and the solvent was removed with a rotary evaporator. The residue was purified by column chromatography (eluent: hexane/ethyl acetate 100/0-90/10) to afford Compound 2-2 (4.64 g, 67%).

[0080] .sup.1H NMR (ppm, 400 MHz, CDCl.sub.3) ? 7.26 (d, J=10.7 Hz, 4H), 6.69 (d, J=8.4 Hz, 2H), 4.19 (t, J=7.4 Hz, 2H), 3.57 (t, J=7.4 Hz, 2H); .sup.13C NMR (ppm, 101 MHz, CDCl.sub.3) ? 143.0, 130.4, 130.0, 127.0, 116.5, 115.6, 49.5, 27.2.

##STR00018##

Preparative Example 2-2: Preparation of diethyl(2-(3,7-dibromo-10H-phenothiazin-10-yl)ethyl)phosphonate

[0081] Compound 2-1 (0.46 g, 0.99 mmol) was dissolved in triethyl phosphite (3.6 mL, 21 mmol). The solution was stirred under reflux for 18 h. After completion of the reaction, the reaction solution was evaporated using a rotary evaporator to remove triethyl phosphite. Then, the residue was purified by column chromatography (eluent: hexane/ethyl acetate 100/0-10/90) to afford Compound 2-2 (0.48 g, 91%).

[0082] .sup.1H NMR (ppm, 400 MHz, CDCl.sub.3) ? 7.28-7.23 (m, 4H), 6.72 (d, J=8.6 Hz, 2H), 4.17-4.06 (m, 6H), 2.27-2.18 (m, 2H), 1.34 (t, J=7.1 Hz, 6H); .sup.13C NMR (ppm, 101 MHz, CDCl.sub.3) ? 143.4, 130.5, 130.0, 126.6, 116.5, 115.5, 62.1 (d, J=6.5 Hz), 41.6, 24.3 (d , J=138.2 Hz), 16.6 (d, J=6.1 Hz); .sup.31P NMR (ppm, 162 MHz, CDCl.sub.3) ? 28.56; HRMS m/z calcd for C.sub.18H.sub.20Br.sub.2NO.sub.3PS [M+Na].sup.+543.9141, found 543.9139 (?=0.4 ppm).

##STR00019##

Preparation 2-3: Preparation of (2-(3,7-Dibromo-10H-phenothiazin-10-yl)ethyl)phosphonic acid

[0083] Compound 2-2 (1.55 g, 2.97 mmol) was dissolved in 1,4-dioxane under argon gas, and then bromotrimethylsilane (4.0 mL, 30 mmol) was slowly added thereto. The mixture was stirred for 24 h. After completion of the reaction, the reaction mixture was evaporated using a rotary evaporator to remove the solvent.

[0084] The resulting solid residue was dissolved in methanol. Distilled water was slowly added until the solution became opaque. The mixture was stirred for 15 h. The precipitate was collected by filtration with water to afford Compound 2-3 (0.80 g, 57%).

[0085] .sup.1H NMR (ppm, 400 MHZ, (CD.sub.3).sub.2SO) ? 7.32-7.27 (m, 4H), 6.88 (d, J=8.7 Hz, 2H), 4.00-3.94 (m, 2H), 2.07-1.97 (m, 2H); .sup.13C NMR (ppm, 101 MHZ, (CD.sub.3).sub.2SO) ? 143.0, 130.4, 129.0, 124.9, 116.9, 114.3, 42.1, 25.5 (d, J=131.0 Hz); .sup.31P NMR (ppm, 162 MHZ, (CD.sub.3).sub.2SO) ? 22.48; HRMS m/z calcd for C.sub.14H.sub.12NO.sub.3PS [M?H].sup.?461.8569, found 461.8573 (?=0.9 ppm).

##STR00020##

Experimental Example 1

[0086] Computational chemistry was used to determine the dipole moments of the molecules of the compounds synthesized in Preparative Examples 1-2 and the already known compounds 2-PACz (Comparative Example 1) and MeO-2PACz (Comparative Example 2). Density functional theory (DFT) calculation was carried out using the def2-SVP basis set and the B3LYP methodology. The results are shown in Table 1.

##STR00021##

[0087] As shown in Table 1, the inventive compounds of Preparative Examples 1-2 had higher dipole moments than the compounds of Comparative Examples 1-2, demonstrating that coating of the conductive base with each inventive compound (SAM) can reduce the work function of the conductive base, enabling more efficient transport of holes generated in a perovskite absorber layer.

Experimental Example 2

[0088] Cyclic voltammetry was conducted to compare the electrochemical properties of the compounds of Preparative Examples 1-2 with those of the compounds of Comparative Examples 1-2. The results are shown in FIG. 15 and Table 2.

TABLE-US-00001 TABLE 2 Oxidation Reduction Redox potential (V) potential (V) potential (V) Preparative Example 1 0.45 0.37 0.41 Preparative Example 2 0.58 0.51 0.54 Comparative Example 1 0.60 0.53 0.56 Comparative Example 2 0.47 0.39 0.43

[0089] As can be seen from the results in FIG. 15 and Table 2, the compounds of Preparative Examples 1-2 showed redox potentials similar to those of the compounds of Comparative Examples 1-2. Particularly, the redox potentials of the compounds of Preparative Examples 2 and 1 were similar to those of the compounds of Comparative Examples 1 and 2, respectively. Each of the materials acts as a hole transport material for efficient hole transport in a perovskite solar cell only when its redox potential is the same as or slightly higher than the energy level of the valence band of a perovskite absorber layer. These results concluded that the abilities of the compounds of Examples 1 and 2 to transport holes are similar to those of the compounds of Comparative Example 2 and Comparative Example 1, respectively.

Example 1

[0090] A patterned indium tin oxide (ITO) glass base (25?25 mm, 15 ?sq.sup.?1) was sequentially washed with distilled water, acetone, and ethanol in an ultrasonic cleaner for 15 min and dried in an oven under a nitrogen atmosphere at 70? C. for 1 h. Thereafter, the glass base was surface treated in a plasma cleaner for 10 min and put into a nitrogen-filled glove box. 1 mg/ml of a solution of the compound (SAM) of Preparative Example 1 was dissolved in ethanol by sonication for 20 min. 100 ?l of the SAM solution was stacked on the center of the ITO base, spin-coated at 3000 rpm/30 sec, and baked on a hot plate at 100? C./10 min. PbI.sub.2 and PbBr.sub.2 were dissolved at a concentration of 1.5 M in a mixture of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a 4:1 volume ratio with stirring at 70? C. for 24 h to prepare PbI.sub.2 and PbBr.sub.2 stock solutions, respectively. Then, the 1.5 M stock solutions were added to formamidinium iodide (FAI) and methylammonium bromide (MABr) powders to prepare FAPbI.sub.3 and MAPbBr.sub.3 solutions (final concentration 1.24 M), respectively. Then, the FAPbI.sub.3 and MAPbBr.sub.3 solutions were mixed in a 5:1 volume ratio to prepare a FA.sub.0.83MA.sub.0.17Pb(I.sub.0.83Br.sub.0.17).sub.3 perovskite precursor solution composed of mixed cations. A 1.5 M cesium iodide stock solution (in DMSO) was added to the mixed cation solution in a 5:1 volume ratio to prepare a triple cation (Cs.sub.0.05(FA.sub.0.83MA.sub.0.17).sub.0.95Pb(I.sub.0.83Br.sub.0.17).sub.3) perovskite precursor solution. 80 ?l of the triple cation perovskite precursor solution was dropped onto the SAM-coated base as a conductive substrate and rotated at 4000 pm for 35 sec. 10 sec before the end of the rotation, 200 ?l of chlorobenzene as an antisolvent was dropped onto the center of the substrate. After completion of the rotation, baking was performed on a hot plate at 100? C. for 30 min to form an absorber layer. Subsequently, the substrate was cooled, taken out of the glove box, placed in a vacuum deposition system, sequentially thermally deposited with C60 (thickness 30 nm) and BCP (thickness 8 mm) to form an electron transport layer, and thermally deposited with Ag to form an Ag electrode (thickness 90 nm) as a counter electrode, completing the fabrication of a perovskite solar cell.

Example 2

[0091] A perovskite solar cell was fabricated in the same manner as in Example 1, except that the compound of Preparative Example 2 was used to form a SAM.

Comparative Example 1

[0092] A perovskite solar cell was fabricated in the same manner as in Example 1, except that 2PACz was used to form a SAM.

Comparative Example 2

[0093] A perovskite solar cell was fabricated in the same manner as in Example 1, except that MeO-2PACz was used to form a SAM.

Test Example 2

[0094] The photoelectric conversion efficiencies of the perovskite solar cells fabricated in Examples 1-2 and Comparative Examples 1-2 were evaluated. To this end, the photovoltages and photocurrents of the solar cells were measured by the following procedure to observe the photoelectric properties of the solar cells. The photoelectric conversion efficiencies (ne) of the solar cells were calculated according to Equation 1 using the obtained current densities (Isc), voltages (Voc), and fill factors (ff). A xenon lamp (Oriel) was used as a light source. The solar condition (AM 1.5) of the xenon lamp was calibrated using a standard solar cell.

Photoelectric conversion efficiency (?e)=(Voc?Isc?ff)/(P.sub.ine) <Equation 1>

where P.sub.ine represents 100 mW/cm.sup.2 (1 sun).

TABLE-US-00002 TABLE 3 Comparative Comparative Example 1 Example 2 Example 1 Example 2 For- Re- For- Re- For- Re- For- Re- Properties ward verse ward verse ward verse ward verse Current density 21.20 21.17 21.23 21.28 20.88 20.95 21.77 21.81 (mA/cm.sup.2) Voltage (V) 1.03 1.02 1.11 1.12 1.08 1.09 1.07 1.05 Fill factor (%) 0.74 0.73 0.75 0.76 0.68 0.73 0.70 0.70 Photoelectric 16.02 15.78 17.85 18.11 15.27 16.72 16.21 16.11 conversion efficiency (%)

[0095] As can be seen from the results in Table 3, the photoelectric conversion efficiencies of the perovskite solar cells including hole transport layers formed using the materials of Preparative Examples 1-2 were improved compared to those of the perovskite solar cells fabricated using the materials known in the art. In addition, the differences between the forward and reverse conversion efficiencies (hysteresis indices) of the perovskite solar cells fabricated in Examples 1-2 were significantly reduced compared to those of the perovskite solar cells fabricated in Comparative Examples 1-2. These results are believed to be because the materials of Preparative Examples 1-2 have similar redox potentials to but higher dipole moments than the materials of Comparative Examples 1-2, which further lowers the work function of the conductive base, enabling more efficient hole transport.

TABLE-US-00003 <Explanation of reference numerals> 100: Conductive base 110: Conductive compound (SAM) 120: Current carrying layer 130: Perovskite layer 140: Electron transport layer (ETL) 150: Counter electrode

INDUSTRIAL APPLICABILITY

[0096] The conductive substrate of the present invention uses a specific conductive compound that is capable of multi-electron redox reactions, possesses p-type organic molecular properties, and has an oxidation potential or highest occupied molecular orbital (HOMO) matching the valence band of perovskite so that holes generated in an absorber layer are selectively separated for the application of the perovskite material, achieving enhanced photoelectric conversion efficiency of the solar cell and a significantly reduced difference between the forward and reverse conversion efficiencies (hysteresis index) of the solar cell. Due to these advantages, the conductive substrate of the present invention can be used in technologies related to perovskite substrates and solar cells.