Sn-Pb PEROVSKITE SOLAR CELL COMPRISING PCBM WITH ALIGNED ORIENTATION BY HIGH-TEMPERATURE THERMAL TREATMENT

Abstract

The present invention relates to a tin-lead based perovskite solar cell comprising PCBM, and more specifically, to a solar cell having excellent performance by performing high-temperature heat treatment on the PCBM, comprising a substrate, a first electron transport layer formed on the substrate, a second electron transport layer formed on the first electron transport layer and comprising PCBM (Phenyl-C61-butyric acid methyl ester), a perovskite light absorption layer formed on the second electron transport layer, a hole transport layer formed on the perovskite light absorption layer, and a metal electrode formed on the hole transport layer.

Description

Technology Field

[0001] The present invention relates to a high-performance tin-lead perovskite solar cell comprising PCBM. Background Technology

[0003] With the increasing demand for alternative energy sources, research on perovskite solar cells (PSC or PeSC) capable of high power conversion efficiency (PCE) is actively underway, and lead-based PeSCs have currently achieved efficiencies of up to 26%. However, due to the toxicity of lead, there is a growing need for alternative materials. Consequently, tin-based PeSCs have been developed, but problems remain, such as the rapid oxidation of tin and poor performance when fabricated into a nip structure.

[0004] Conventional perovskite solar cells have not been able to achieve sufficient efficiency due to the fact that charge transport efficiency is reduced due to a large number of trap sites existing between the tin-based perovskite and the metal oxide electron transport layer (ETL), and the perovskite can be oxidized due to oxygen vacancies in the metal oxide layer.

[0005] Accordingly, while researching tin-lead-based perovskite solar cells, the inventors developed a solar cell with a high efficiency of a nip structure by coating PCBM on an electron transport layer containing a metal oxide and then performing high-temperature heat treatment, thereby reducing trap density and improving electron mobility, and thus completed the present invention. The problem to be solved

[0007] The present invention aims to provide a high-performance tin-lead perovskite solar cell comprising PCBM. means of solving the problem

[0009] 1. A substrate; a first electron transport layer formed on the substrate; and a PCBM (Phenyl-C) formed on the first electron transport layer. 61 A perovskite solar cell comprising: a second electron transport layer containing (butyric acid methyl ester); a perovskite light absorption layer formed on the second electron transport layer; a hole transport layer formed on the perovskite light absorption layer; and a metal electrode formed on the hole transport layer.

[0010] 2. A perovskite solar cell according to 1, wherein the first electron transport layer comprises at least one selected from the group consisting of SnO2, TiO2, ZnO, MgO, WO3, PbO, In2O3, Bi2O3, Ta2O5, BaTiO3, BaZrO3, ZrO3, and PEDOT:PSS.

[0011] 3. A perovskite solar cell according to 1 above, wherein the second electron transport layer is formed by spin-coating the PCBM on the first electron transport layer and then annealing at 150 to 250°C.

[0012] 4. A perovskite solar cell according to 1 above, wherein the perovskite light-absorbing layer comprises a compound represented by the following chemical formula 1:

[0013] [Chemical Formula 1]

[0014] FA x MA 1-x Sn y Pb 1-y Q3

[0015] (In the formula, Q is a halogen element, FA is pomamidinium, MA is methylammonium, and x is 0 <x<1를 만족하는 실수이고, y는 0<y<1를 만족하는 실수임).

[0016] 5. In the above 1, the hole transport layer is P3HT, fullerene (C 60A perovskite solar cell comprising at least one selected from the group consisting of ), vasocuproin (BCP), graphene, carbon nanotubes, PEDOT:PSS, PTAA, CuSCN, NiOx, CuI, and MoOx.

[0017] 6. A perovskite solar cell according to 1 above, wherein the metal electrode comprises at least one selected from the group consisting of Au, Al, Ag, Fe, Ag, Cu, Cr, W, Mo, Zn, Ni, Pt, Pd, Co, In, Mn, Si, Ta, Ti, Sn, Pb, V, Ru, Ir, Zr, Rh, and Mg.

[0018] 7. In the above 1, the perovskite solar cell is a perovskite solar cell having a nip structure.

[0019] 8. A method for manufacturing a perovskite solar cell comprising: a step of preparing a substrate; a step of forming a first electron transport layer on the substrate; a step of forming a second electron transport layer by spin-coating PCBM on the first electron transport layer; a step of annealing the second electron transport layer at a temperature of 150 to 250°C; a step of forming a perovskite light-absorbing layer on the second electron transport layer; a step of forming a hole transport layer on the perovskite light-absorbing layer; and a step of forming a metal electrode on the hole transport layer. Effects of the invention

[0021] The present invention enables the uniform growth of perovskite by including a PCBM layer in the electron transport layer.

[0022] The present invention enables a solar cell to have high power conversion efficiency by forming a PCBM layer and then performing high-temperature heat treatment. Brief explanation of the drawing

[0024] Figures 1(a) to 1(c) are contact angle images of water droplets in films with different compositions depending on the presence or absence of PCBM and heat treatment temperature, Figures 1(d) to 1(f) are SEM images of perovskite films having different ETL layers depending on the presence or absence of PCBM and heat treatment temperature, and Figures 1(g) to 1(i) are cross-sectional SEM images of a complete device, where the blue box is ITO, the green box is SnO2, the purple box is PCBM, the orange box is perovskite, the yellow box is P3HT, and the pale yellow box is Au. Figure 2 is an atomic force microscope (AFM) image showing the surface roughness of (a) ITO / SnO2, (b) ITO / SnO2 / LT-PCBM, and (c) ITO / SnO2 / HT-PCBM. Figure 3 shows (a) XRD patterns of ITO / SnO2, ITO / SnO2 / LT-PCBM and ITO / SnO2 / HT-PCBM substrates and (b) Williamson-Hall plot of XRD data, where β is FWHM (full width at half maximum) and ε is microstrain. Figures 4 (a) and (b) show the UV-vis absorption spectra of PCBM films before and after washing with DMF:DMSO and EA, respectively, (c) and (d) show GIWAXS images of LT-PCBM and HT-PCBM on a silicon wafer, (e) shows the XRD patterns of LT-PCBM and HT-PCBM, and (f) shows the results of measuring the conductivity of the ITO / film / Al structure of each film. Figure 5 shows the UV-vis-NIR absorption spectra of PCBM at various annealing temperatures, and the dashed lines represent (a) PCBM washed with DMF:DMSO and (b) EA, respectively. Figure 6 shows the 2D-GIWAXS patterns of PCBM at various annealing temperatures. Figure 7 shows the XRD patterns of PCBM films at various annealing temperatures. FIG. 8 shows the space-charge-limited current (SCLC) measurement results, where (a) is a hole-only device (HOD) with an ITO / PEDOT:PSS / Perovskite / P3HT / Au structure, and (b) to (d) are ITO / ETL / perovskite / C with ETLs of various configurations. 60 This is the current density-voltage (JV) curve of an electronic dedicated device (EOD) with a / BCP / Al structure. FIG. 9 shows the light intensity dependence of a device without PCBM and a device with PCBM (a) short-circuit current density (J SC ) and (b) open circuit voltage (V OC (c) transient photovoltage (TPV) measurement results and (d) Nyquist plot are shown. Figure 10 shows FA under various ETL conditions 0.7 MA 0.3 Sn 0.5 Pb 0.5 This shows the steady-state PL spectrum of the I3 film, where the excitation light is incident on the glass. Figure 11 (a) shows the schematic structure of the device, and (b) shows the energy levels of each layer of the device. Figure 11 (c) shows 100 mW cm⁻¹. -2 JV curves of PSCs with various ETL layers are shown under AM 1.5 Sunlight, and (d) and (e) are graphs comparing the PCE stability of unencapsulated devices upon exposure to a nitrogen atmosphere and a nitrogen-filled glovebox at 85 °C, respectively (empty circles represent the average value of 8 devices with error bars, and filled circles represent the highest PCE value). Figure 12 (a) and (b) are UPS data for PCBM and perovskite film, respectively, and (c) and (d) are UV-vis-NIR absorption spectra for PCBM and perovskite film, respectively. Fig. 13(a) is 100 mW cm -2 (b) shows the JV curves of PSCs with various ETL layers under AM 1.5 Sunlight, and (b) shows the EQE spectrum and integrated J of a device with PCBM. SC It represents. Figure 14 shows (a)J under different ETL conditions. SC , (b)V OC , (c) FF and (d) PCE statistical distributions are shown, each condition consisting of 35 elements. Figure 15 shows the JV curves of a device having different ETL layers during reverse and forward voltage scans. Figure 16 (a) shows the results of comparing the average PCE stability of 8 unencapsulated devices under an N2 atmosphere with exposure to 85°C in a glovebox, and (b) is a photograph of the device marked with a purple circle in (a), which was left on an 85°C hot plate for 836 hours. Figure 16 (c) shows the results of comparing the average PCE stability of 12 unencapsulated devices under a normal atmosphere of 25°C and 30% humidity. Figure 16 (d) shows the XPS data of ITO / SnO2 / perovskite and ITO / SnO2 / HT-PCBM / perovskite films exposed to dry air for 50 hours and etched three times. Specific details for implementing the invention

[0025] The present invention provides a tin-lead based perovskite solar cell comprising a PCBM.

[0026] The present invention comprises a substrate; a first electron transport layer formed on the substrate; and a PCBM (Phenyl-C) formed on the first electron transport layer. 61A perovskite solar cell is provided, comprising: a second electron transport layer containing (butyric acid methyl ester); a perovskite light absorption layer formed on the second electron transport layer; a hole transport layer formed on the perovskite light absorption layer; and a metal electrode formed on the hole transport layer.

[0027] The present invention relates to a solar cell comprising PCBM, wherein the recombination of electrons and holes is reduced and excellent performance is achieved by subjecting the PCBM to high-temperature heat treatment.

[0028] In one embodiment, the substrate may comprise indium tin oxide (ITO).

[0029] The electron transport layer (ETL) may be composed of a first electron transport layer and a second electron transport layer. The first electron transport layer is formed on a substrate, and the second electron transport layer is formed on the first electron transport layer.

[0030] The first electron transport layer may comprise, for example, at least one selected from the group consisting of SnO2, TiO2, ZnO, MgO, WO3, PbO, In2O3, Bi2O3, Ta2O5, BaTiO3, BaZrO3, ZrO3, and PEDOT:PSS, but is not limited thereto.

[0031] In one embodiment, the first electron transport layer may be SnO2 or PEDOT:PSS.

[0032] The second electron transport layer may be formed by spin-coating PCBM onto the first electron transport layer and then annealing at 150 to 250°C, 150 to 240°C, 150 to 230°C, 150 to 220°C, 150 to 210°C, 150 to 200°C, 150 to 190°C, 150 to 180°C, 150 to 170°C, or 150 to 160°C.

[0033] In one embodiment, the second electron transport layer may be formed by spin-coating PCBM onto the first electron transport layer and then annealing at 150°C.

[0034] PCBM can perform a passivation function for metal oxides and perovskites.

[0035] The present invention enables uniform growth of perovskite and allows the grains of perovskite to be formed larger and vertically by forming a perovskite light-absorbing layer on a second electron transport layer that is smooth and hydrophobic by including PCBM.

[0036] The present invention aligns the PCBM and gives it crystallinity by performing a high-temperature heat treatment (annealing) of 150°C or higher on a second electron transport layer containing PCBM. In addition, through this heat treatment, resistance to organic solvents is increased, and conductivity and electron mobility are improved.

[0037] The present invention can prevent the recombination of electrons and holes through passivation between the metal oxide and the perovskite by including PCBM. The solar cell of the present invention can have enhanced efficiency through this passivation effect.

[0038] The perovskite light-absorbing layer may contain a compound represented by the following chemical formula 1.

[0039] [Chemical Formula 1]

[0040] FA x MA 1-x Sn y Pb 1-y Q3

[0041] (In the formula, Q is a halogen element, FA is formamidinium, MA is methylammonium, and x is 0 <x<1를 만족하는 실수이고, y는 0<y<1를 만족하는 실수임).

[0042] In one embodiment, the perovskite light-absorbing layer is FA 0.7 MA 0.3 Sn 0.5 Pb 0.5 It could be 13.

[0043] The hole transfer layer (HTL) consists of P3HT and fullerene (C 60 It may include at least one selected from the group consisting of vasocuproine (BCP), graphene, carbon nanotubes, PEDOT:PSS, PTAA, CuSCN, NiOx, CuI, and MoOx, but is not limited thereto.

[0044] In one embodiment, the hole transport layer is P3HT or fullerene (C 60 It may contain ) / vasocuproin (BCP).

[0045] The metal electrode may comprise at least one selected from the group consisting of Au, Al, Ag, Fe, Ag, Cu, Cr, W, Mo, Zn, Ni, Pt, Pd, Co, In, Mn, Si, Ta, Ti, Sn, Pb, V, Ru, Ir, Zr, Rh, and Mg, but is not limited thereto.

[0046] In one embodiment, the metal electrode may be Au or Al.

[0047] The perovskite solar cell of the present invention may have a nip structure.

[0048] The present invention provides a method for manufacturing a tin-lead based perovskite solar cell comprising a PCBM.

[0049] The method for manufacturing a perovskite solar cell according to the present invention comprises the steps of: preparing a substrate; forming a first electron transport layer on the substrate; forming a second electron transport layer by spin-coating PCBM on the first electron transport layer; annealing the second electron transport layer at a temperature of 150 to 250°C; forming a perovskite light absorption layer on the second electron transport layer; forming a hole transport layer on the perovskite light absorption layer; and forming a metal electrode on the hole transport layer.

[0050] In the manufacturing method of the present invention, the substrate, the first electron transport layer, the second electron transport layer, the perovskite light absorption layer, the hole transport layer, and the metal electrode are applied in the same manner as those mentioned in the perovskite solar cell, unless there is a contradiction.

[0051] In one embodiment, the step of forming the first electron transport layer may be performed using spin coating.

[0052] In one embodiment, the step of forming a perovskite light-absorbing layer may be spin-coating by dropping a perovskite precursor.

[0053] In one embodiment, the step of forming a metal electrode may be performed by depositing the metal under high vacuum conditions.

[0055] Hereinafter, in order to specifically explain the present invention, it will be described in detail with reference to examples.

[0057] Examples

[0058] Example 1. Materials and Method

[0059] 1-1. Materials

[0060] Tin(IV) oxide (SnO2, 15% in H2O colloidal dispersion) and tin iodide (SnI2, 99.999%) were purchased from Alfa Aesar. Formamidinium iodide (FAI) and methylammonium iodide (MAI) were purchased from Great Cell Solar Materials. Tin(II) fluoride (SnF2, 99%), tin powder (99.5%), N,N-dimethylformamide (DMF, 99.8%), dimethyl sulfoxide (DMSO, 99.9%), chlorobenzene (CB, 99.8%), 1,2-dichlorobenzene (DCB, 99%), and ethyl acetate (EA, 99.8%) were purchased from Sigma-Aldrich. Lead iodide (PbI2, 99.99%) was purchased from TCI. Phenyl-C61-butyric-acid-methylester (PCBM, 99.5%) and poly(3-hexylthiophene) (P3HT) were purchased from OSM. Indium tin oxide (ITO) on glass was 10Ω sq -1 It had a value of .

[0062] 1-2. Preparation of Perovskite Solution

[0063] FA 0.7 MA 0.3 Sn 0.5 Pb 0.5The I3 perovskite precursor was prepared in an N2-filled glovebox. 216.68 mg of FAI, 85.84 mg of MAI, 335.27 mg of SnI2, 414.91 mg of PbI2, 14.1 mg of SnF2, and a small amount of tin powder were dissolved in 1 mL of a DMF / DMSO mixture (3:1 volume ratio). The perovskite precursor was prepared by stirring overnight. The solution was filtered through a 0.45 μm PTFE filter before use.

[0065] 1-3. Device Fabrication

[0066] The ITO glass substrate was washed sequentially with deionized (DI) water, acetone, and isopropyl alcohol via ultrasonification, and then dried in an oven. The washed ITO glass substrate was treated with ultraviolet ozone for 20 minutes. Subsequently, an SnO2 solution diluted with SnO2 and DI water in a 1:6 ratio was spin-coated onto the substrate at 3000 rpm for 30 seconds, and then annealed at 150°C for 10 minutes. The SnO2-coated substrate was transferred to an N2-filled glovebox. For the PCBM passivated cell, PCBM (40 mg / mL in DCB) was spin-coated at 3000 rpm for 30 seconds, and then annealed at 100°C (LT-PCBM) and 150°C (HT-PCBM), respectively.

[0067] To fabricate the perovskite film, a perovskite precursor was dropped and spin-coated at 1000 rpm for 10 seconds, followed by spin-coating at 4000 rpm for 40 seconds, and 200 μL of EA was dropped 20 seconds before the spin ended. Subsequently, the perovskite film was immediately dried on a 100°C hot plate for 10 minutes. For the HTL, P3HT (10 mg / mL in CB) was deposited by spin-coating at 3000 rpm for 30 seconds. Finally, Au (70 nm) was deposited under high vacuum conditions (<10 -6 Deposited in Torr.

[0069] 1-4. Verification of Film Characteristics

[0070] Contact angle images were obtained using a DSA100 (KRUSS GmbH, Germany). Scanning electron microscopy (SEM) images were obtained using an electron microscope (SU7000, Hitachi High Technologies) at an acceleration voltage of 7 kV. UV-vis-NIR absorption spectra were obtained using a Cary 5000 (Agilent) spectrophotometer, and photoluminescence spectra were measured using an nF900 instrument (Edinburgh Photonics) with a xenon lamp as the excitation source.

[0071] Grazing-incidence wide-angle X-ray scattering (GIWAXS) experiments were performed at the Pohang Accelerator Laboratory in Pohang, South Korea. Samples were prepared on silicon substrates. GIWAXS measurements were performed at Beamline 9A, and X-rays from an invacuum undulator (IVU) were monochromated using a Si (111) double-slit monochromator. X-rays with a beam energy of 11.08 keV and an incident angle of 0.12° were used. GIWAXS patterns were recorded on a 2D CCD detector (SX165, Rayonix, USA). X-ray diffraction (XRD) patterns were obtained using a high-power diffractometer (D8 ADVANCE at Bruker AXS) with Cu Kα radiation (λ = 0.1542 nm) as the X-ray source. X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectron spectroscopy (UPS) measurements were performed using an ESCLAB 250XI. The surface morphology of the film was characterized by atomic force microscopy (AFM) using a Dimension ICON (Bruker Nano Surface). Samples were prepared under optimized conditions, and measurements were performed in scanAsyst mode. Steady-state photoluminescence (PL) spectra were measured using an FLS920 (Edinburgh Instruments). External quantum efficiency (EQE) was measured under dry air using an EQE system (Model QEX7) by PV Measurements Inc. (Boulder, Colorado).

[0073] 1-5. Verification of Device Characteristics

[0074] Current density-voltage (JV) characteristics and current density-light intensity graphs were measured using a Keithley 2635A source measurement unit. Measurements were performed to induce light from a xenon arc lamp sunlight simulator using high-quality optical fibers in a nitrogen-filled glovebox. Intensities were measured using standard silicon photodiodes at AM 1.5G illumination (100 mW cm⁻¹). -2 Corrected at ). Transient photovoltage (TPV) measurements were at V under illumination OC The test was performed using the McScience T4000 (organic semiconductor parameter test system), and electrochemical impedance spectroscopy (EIS) measurements were performed using the BioTogic VSP300 under air conditions with encapsulated devices.

[0076] Example 2. Perovskite film having a PCBM layer

[0077] Figures 1 (a) to (c) show contact angle images of water droplets with and without PCBM, confirming that the contact angle of the water droplet is 8° for the ITO / SnO2 film and 76° for the ITO / SnO2 / PCBM film. The PCBM layer formed a hydrophobic surface regardless of the annealing temperature. The wettability of the film surface affects the nuclei density and grain size during perovskite grain formation.

[0078] Figures 1(d) to 1(f) show SEM images of perovskite films having various ETL layers. The perovskite on the ITO / SnO2 ETL layer exhibited an average grain size of 494 nm. In contrast, the average grain sizes of the perovskite on the ITO / SnO2 / LT-PCBM and ITO / SnO2 / HT-PCBM layers were 991 and 1010 nm, respectively. Importantly, the perovskite layer on the hydrophobic PCBM surface had a lower nucleation density compared to the perovskite layer on the hydrophilic SnO2 surface without PCBM. This difference led to the formation of larger, vertical monolithic grains (Figures 1(g) to 1(i)). In the case of tin-lead-based perovskites, the formation rate of tin-based perovskites is faster than that of lead-based perovskites, resulting in non-uniform growth. This non-uniform growth makes it difficult to obtain vertical grains. Furthermore, since the bonding energy between the metal oxide and SnI2 is stronger than that of PbI2, this non-uniform growth is further exacerbated, particularly when compared to pin structures. The present invention has confirmed that this problem has been resolved by introducing PCBM.

[0079] Additionally, the surface roughness of the ITO / SnO2 film was measured to be 0.923 nm, while the roughness of the LT-PCBM was 0.300 nm and the roughness of the HT-PCBM was 0.306 nm, so the surface of the ITO / SnO2 / PCBM film was observed to be considerably smooth (Fig. 2).

[0080] The roughness of the underlying layer can affect the growth of the upper film during the formation process, potentially causing microstrain in the upper film. In particular, perovskite films grown on a smooth PCBM layer exhibited approximately 10% lower microstrain compared to perovskite films grown on a relatively rough SnO2 surface (Fig. 3). Therefore, the introduction of PCBM provides advantages for the growth of perovskite films, allowing for the formation of larger and vertically grown grains, which can reduce recombination loss and improve charge transport properties.

[0082] Example 3. PCBM according to high annealing temperature

[0083] The effect of additional heat treatment on the properties of PCBM was verified. Figures 4(a) and 4(b) and Figure 5 show the UV-vis absorption spectra for the film and demonstrate the solvent resistance of PCBM according to the annealing temperature. PCBM is readily soluble in common organic solvents such as N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and ethyl acetate (EA). These solubility characteristics are an important consideration when using PCBM as a sublayer in perovskite applications. The present invention solves the problem related to the cleaning of PCBM through high-temperature annealing.

[0084] The absorption spectra of LT-PCBM and HT-PCBM exhibit similar characteristics. However, when PCBM was treated with a mixed solvent of DMF and DMSO or EA, distinct differences were observed in the absorption spectra. PCBM, which had an initial thickness of approximately 30 nm before treatment, showed a decrease in thickness after DMF:DMSO treatment, with LT-PCBM decreasing to 20.8 nm and HT-PCBM to 25.9 nm. EA treatment further emphasized this trend, with the thickness decreasing to 2.5 nm for LT-PCBM and 23.7 nm for HT-PCBM. High-temperature annealing allowed the PCBM layer to remain more effectively in the underlying region of the perovskite, thereby preserving the compact passivation effect of PCBM on the SnO2 and perovskite layers. This effect was also observed in cross-sectional SEM images of the device, showing a difference of about twofold in PCBM thickness: 12.4 nm for the LT-PCBM layer and 22.3 nm for the HT-PCBM layer (Fig. 1 (h) and (i)).

[0085] When PCBM was annealed at high temperatures, significant changes in alignment and crystallinity were observed. The directional alignment and crystallization according to the annealing temperature were confirmed through GIWAXS and XRD measurements (Figs. 4 (c) to (e)). According to Fig. 6, PCBM treated at temperatures below 120°C exhibited an isotropic ring-shaped GIWAXS pattern, indicating its amorphous or very small crystal characteristics. On the other hand, PCBM treated at temperatures above 150°C showed distinct peaks, indicating the crystallization of PCBM. The same trend could also be observed in the XRD data.

[0086] Figure 7 shows diffraction peaks at 10.9° and 17.5° in the XRD spectrum of a PCBM film annealed at high temperature, which indicates that PCBM is crystallin at high temperatures above 150°C. The aligned PCBM facilitates short-range electron transport, which can improve conductivity.

[0087] Figure 4(f) shows the conductivity of SnO2, LT-PCBM, and HT-PCBM of the same thickness. Although the conductivity of PCBM is lower than that of pure SnO2, the high-temperature annealed PCBM film had conductivity similar to that of SnO2. This enhanced conductivity of PCBM enables rapid electron transport and extraction as an ETL, contributing to improved device performance.

[0089] Example 4. Verification of electrical characteristics

[0090] Space-charge-limited current (SCLC) measurements were performed to investigate the trap density and charge carrier transport characteristics of perovskites under various ETL conditions. Figure 8(a) shows the current density-voltage (JV) curve of a hole-only device (HOD) having an ITO / PEDOT:PSS / perovskite / P3HT / Au structure, and Figures 8(b) to (d) show the ITO / ETL / perovskite / C 60 This shows the current density-voltage (JV) curve of an electron-only device (EOD) with a / BCP / Al structure. The first kink point of the JV curve is the trap density (N t Trap-filled limit voltage (V) representing ) TFL It corresponds to ). The trap density is It was calculated using the formula, where ε and ε0 are the permittivity of the perovskite and the vacuum permittivity, respectively, and L is the thickness of the perovskite film. The trap density of the perovskite at HOD is 4.043 × 10⁻⁶. 15 cm -3 On the other hand, the measured V of perovskites without PCBM, perovskites with LT-PCBM, and perovskites with HT-PCBM in EOD TFL The values ​​were 0.35, 0.23, and 0.12 V, respectively, and the trap density was 2.527 x 10⁻⁶ 15 , 1.660 Х 10 15 and 8.663 X 10 14 cm -3 Perovskites on PCBM layers, particularly HT-PCBM, showed a significant decrease in electron trap density and non-radiative recombination, confirming effective passivation by PCBM.

[0091] To obtain the charge carrier transport characteristic of the device, the charge carrier mobility (μ) of the perovskite was evaluated using the Mott-Gurney law. In the trap-free Child's regime, according to the following equation Based on this, the charge carrier mobility was calculated. The hole mobility (μ) of the perovskite h ) is 8.891 cm 2 V -1 S -1 was, and the electron mobility (μ) of perovskites without PCBM, perovskites with LT-PCBM, and perovskites with HT-PCBM e ) are 0.114, 0.284, and 1.543 cm, respectively. 2 V -1 s -1 was. As shown in Table 1 below, tin-lead based perovskite (Sn-Pb perovskite) μ by self-p-dopinge Contrast high μ h It has, and due to this, μ h / μ e The ratio was 63.51.

[0092] structure V TFL (V) N t (cm -3 ) μ (cm 2 V -1 S -1 ) μ h / μ e HOD a 0.56 4.043 x 10 15 8.891 EOD b w / o PCBM 0.35 2.527 x 10 15 0.114 63.51 LT-PCBM 0.23 1.660 x 10 15 0.284 31.30 HT-PCBM 0.12 8.663 x 10 14 1.543 5.76

[0093] ( a Hole only device (HOD) structure: ITO glass / PEDOT:PSS / Perovskite / P3HT / Au. Current flow direction is from ITO to the metal; b Electron-only device (EOD) structure: ITO glass / SnO2 / (PCBM) / Perovskite / C60 / BCP / Al. Current flow direction is from ITO to the metal.

[0095] However, the introduction of LT-PCBM and HT-PCBM increased electron mobility in the perovskite, contributed to a decrease in trap density, and improved conductivity. Consequently, μ h / μ e The ratio decreased to 5.76 in HT-PCBM. This balanced mobility mitigates recombination within the perovskite and has a positive effect on device performance.

[0096] To investigate the effect of the PCBM interlayer on trap-assisted recombination kinetics, additional analysis of charge carrier kinetics within the device was performed. The luminous intensity-dependent short-circuit current density (J SC ) and open circuit voltage (V OC ) was calculated using the following formula and is shown in (a) and (b) of Fig. 9.

[0097]

[0098] In the above equation, I and I0 represent luminous intensity and initial luminous intensity, respectively, α is the exponential factor, n is the ideality factor, and k Bε is the Boltzmann constant, and T is the temperature. Devices with HT-PCBM exhibited an exponent α close to 1, which implies the complete suppression of bimolecular charge recombination. Due to the difference in hole and electron mobility that can affect recombination within the perovskite, devices with HT-PCBM displayed enhanced electron mobility, exhibiting the most ideal characteristics. The ideality exponent (n) values ​​were 1.596, 1.522, and 1.288 for devices without PCBM, devices with LT-PCBM, and devices with HT-PCBM, respectively. Generally, 2 k B An anomaly near T / q indicates that trap-assisted Shockley-Read-Hall rejoining is dominant, which is V OC Leading to loss, 1 k B T / q is considered an ideal value. Devices with HT-PCBM exhibited the lowest n values, which was consistent with SCLC data. Therefore, the introduction of HT-PCBM effectively suppresses trap-assisted charge recombination and consequently high V OC It can represent a value.

[0099] Transient photovoltage (TPV) measurements were performed to investigate the charge recombination dynamics affected by PCBM in more detail. The decay lifetime graph was determined by fitting a double exponential decay function, and the fitting parameters are briefly shown in Table 2.

[0100]

[0101] As shown in Fig. 9(c), as expected, the charge lifetimes of the device without PCBM, the device with LT-PCBM, and the device with HT-PCBM increased from 0.944 ms to 1.715 ms and 2.761 ms, respectively. These results suggest that PCBM lowers the defect concentration, improves electrical characteristics, and reduces charge recombination on the perovskite surface, which corresponds to the high V observed in the corresponding devices. OC It is a result that matches the value.

[0102] In addition, steady-state photoluminescence (PL) spectroscopy measurements were performed on perovskite films to verify not only the effects of balanced electron and hole transport but also photophysical processes occurring only at the ETL / perovskite interface. Figure 10 shows FA deposited under various ETL conditions. 0.7 MA 0.3 Sn 0.5 Pb 0.5 The PL spectra of samples with I3 perovskite films are shown. PL intensity decreased significantly in the order of SnO2 / HT-PCBM, SnO2 / LT-PCBM, and SnO2. The reduced PL peaks indicate effective charge extraction within the perovskite and ETL layers. In particular, the perovskite layer on SnO2 / HT-PCBM, characterized by high conductivity and few traps, exhibits the most efficient charge transfer performance. This suggests that HT-PCBM facilitates more favorable charge transfer and essentially reduces the number of interfacial defects between the perovskite and SnO2.

[0103] To understand the interfacial charge transfer kinetics and the recombination process with PCBM, electrochemical impedance spectroscopy (EIS) measurements were performed under dark conditions. The Nyquist plot obtained in the low-frequency region represents the recombination resistance (R) at the interface between the perovskite and the charge transport layer. rec It represents ). Since all devices used the same HTL, Rrec This primarily reflects the interface between the ETL and the perovskite. As can be seen in Fig. 9(d), the device with HT-PCBM has a high R of 694 KΩ. rec While indicating a value, the device without PCBM has an R of 129 KΩ, and the device with LT-PCBM has an R of 560 KΩ. rec Indicated the value. R rec As this increases, interfacial charge carrier recombination decreases, so devices with HT-PCBM have high V OC Enables having.

[0105] Example 5. Verification of performance of perovskite solar cell device

[0106] Figures 11 (a) and (b) illustrate the schematic structure of the device and the energy levels of each layer, which were confirmed through ultraviolet photoelectron spectroscopy (UPS) measurements (Figure 12, Table 3).

[0107]

[0108] The conduction band minimums of the LT-PCBM and HT-PCBM films were calculated to be -4.30 and -4.40 eV, respectively. The downward shift of the PCBM energy level due to increased crystallinity suggests that electron transfer from the perovskite to SnO2 can be facilitated. Figure 11 (c) and Figure 13 (a) show the JV curves, and Figure 13 (b) and Table 4 show the external quantum efficiency (EQE) measurement results for devices with various ETL conditions.

[0109]

[0110] The optimal performance of the device is summarized in Table 5 below, and Table 5 shows the simulated AM 1.5 Sunlight 100 mW cm⁻¹. -2The photoelectric parameters of a Champion Device with various ETL layers are shown below.

[0111] ETL J SC (mA cm -2 ) V OC (V) FF PCE (%) w / o PCBM 29.97 0.39 0.52 6.03 LT-PCBM 30.46 0.52 0.58 9.25 HT-PCBM 30.79 0.77 0.65 15.50

[0113] Devices without PCBM are J SC Ga 29.97 mA cm -2 , V OC It exhibited a peak power conversion efficiency (PCE) of 6.03% with a V of 0.39 and a fill factor (FF) of 0.52. The device with LT-PCBM J SC 30.46 mA cm -2 , V OC It showed a PCE of 9.25% with a V of 0.52 and a fill factor (FF) of 0.58. When compared to other devices, the device with HT-PCBM J SC Ga 30.79 mA cm -2 , V OC It showed the highest PCE of 15.50% with a fill factor (FF) of 0.65 and a V of 0.77.

[0114] Figure 14 and Table 6 show the statistical distribution of the JV characteristics of the device, and V OC It demonstrates a high level of reproducibility.

[0115]

[0116] As discussed earlier, V OC The significant improvement may be attributed to efficient charge carrier transport and reduced recombination due to interfacial passivation, which is supported by low trap density. This trend was also observed in the hysteresis index (HI). Figure 15 and Table 7 show the JV characteristics for both the reverse scan and the forward scan.

[0117]

[0118] The low JV hysteresis observed in devices containing HT-PCBM indicates the passivation of hydroxyl groups on the SnO2 surface. Hydroxyl groups attract cations from the perovskite, causing hysteresis in the device and inducing the decomposition of the perovskite. Additionally, oxygen vacancies on the surface of metal oxides are known to accelerate the oxidation of tin-based perovskites. These hydroxyl groups and oxygen vacancies on the SnO2 surface can be effectively passivated by the ester side chains of PCBM, thereby improving the stability of perovskite solar cells.

[0119] To verify the effect of PCBM on device stability, the storage life was measured by storing unencapsulated devices in a nitrogen-filled glovebox (Fig. 11(d)). Optimized devices with LT-PCBM and HT-PCBM exhibited higher stability compared to devices without PCBM, maintaining an efficiency of over 90% for 2,800 and 5,000 hours, respectively. As shown in Fig. 11(e), when exposed to heat of 85°C inside the glovebox, the device with HT-PCBM, which showed the highest efficiency, maintained 90% efficiency even after 330 hours and maintained 90% efficiency for an average of 259 hours. In contrast, the efficiency of the devices without PCBM and the devices with LT-PCBM decreased to 90% within 120 hours. Figure 16 (a) shows the average efficiency degradation over 800 hours at 85°C in a glove box, and Figure 16 (b) is a photograph of the device after 836 hours. The device without PCBM and the device with LT-PCBM showed noticeable degradation of the perovskite, whereas the device with HT-PCBM maintained the black color of the perovskite.

[0120] The decomposition of perovskite was clearly accelerated in the presence of oxygen. Fig. 16(c) shows the average PCE stability data of the devices under ambient conditions; the efficiency of all devices decreased within 24 hours, and the device with HT-PCBM exhibited the highest sustained efficiency. The degree of perovskite decomposition under ambient conditions affected by the presence of PCBM can be attributed to accelerated oxidation by metal oxides, which was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. Fig. 16(d) shows high-resolution XPS spectra of Sn 3d orbitals of perovskite films exposed to dry air for 50 hours and etched three times. The spectra were compared between the sample deposited on the SnO2 layer and the sample deposited on the HT-PCBM layer. The perovskite film on the SnO2 layer [shows] Sn 3d 3 / 2 Sn at 495.9 and 494.7 eV in the spectrum, respectively. 4+ and Sn 2+ A deconvoluted peak corresponding to the state was shown. In addition, Sn 3d 5 / 2 The spectra are Sn, respectively. 4+ and Sn 2+ The state exhibited peaks at 487.5 and 486.3 eV. In contrast, the perovskite film on the HT-PCBM layer exhibited Sn 3d 3 / 2 In the case of, a single peak at 494.6 eV, Sn 3d 5 / 2 In the case of, a single peak was observed at 486.2 eV.

[0121] Investigation of Sn 3d spectra in bulk perovskites under continuous oxidation conditions revealed that while perovskites without PCBM exhibited continuous rapid internal oxidation, perovskites with HT-PCBM showed slower internal oxidation. This implies instability in perovskites grown directly on SnO2 due to more microstrain, interfacial defects caused by hydroxyl groups and oxygen vacancies, and the numerous internal defects identified earlier. Consequently, the presence of HT-PCBM can improve the stability of tin-lead-based perovskite devices.

Claims

Claim 1 Substrate; a first electron transport layer formed on the substrate; and PCBM (Phenyl-C) formed on the first electron transport layer. 61 A perovskite solar cell comprising: a second electron transport layer containing (butyric acid methyl ester); a perovskite light absorption layer formed on the second electron transport layer; a hole transport layer formed on the perovskite light absorption layer; and a metal electrode formed on the hole transport layer, wherein the second electron transport layer is formed by spin-coating the PCBM on the first electron transport layer and then annealing at 150 to 210°C. Claim 2 A perovskite solar cell according to claim 1, wherein the first electron transport layer comprises at least one selected from the group consisting of SnO2, TiO2, ZnO, MgO, WO3, PbO, In2O3, Bi2O3, Ta2O5, BaTiO3, BaZrO3, ZrO3, and PEDOT:PSS. Claim 3 A perovskite solar cell according to claim 1, wherein the second electron transport layer is formed by spin-coating the PCBM on the first electron transport layer and then annealing at 150 to 180°C. Claim 4 A perovskite solar cell according to claim 1, wherein the perovskite light-absorbing layer comprises a compound represented by the following chemical formula 1: [Chemical Formula 1]FA x MA 1-x Sn y Pb 1-y Q3(wherein Q is a halogen element, FA is pomamidinium, MA is methylammonium, and x is 0 <x<1를 만족하는 실수이고, y는 0<y<1를 만족하는 실수임). Claim 5 In claim 1, the hole transport layer is P3HT, fullerene (C 60 A perovskite solar cell comprising at least one selected from the group consisting of ), vasocuproin (BCP), graphene, carbon nanotubes, PEDOT:PSS, PTAA, CuSCN, NiOx, CuI, and MoOx. Claim 6 A perovskite solar cell according to claim 1, wherein the metal electrode comprises at least one selected from the group consisting of Au, Al, Ag, Fe, Ag, Cu, Cr, W, Mo, Zn, Ni, Pt, Pd, Co, In, Mn, Si, Ta, Ti, Sn, Pb, V, Ru, Ir, Zr, Rh, and Mg. Claim 7 The perovskite solar cell of claim 1, wherein the perovskite solar cell has a nip structure. Claim 8 A method for manufacturing a perovskite solar cell according to any one of claims 1 to 7, comprising: a step of preparing a substrate; a step of forming a first electron transport layer on the substrate; a step of forming a second electron transport layer by spin-coating PCBM on the first electron transport layer; a step of annealing the second electron transport layer at a temperature of 150 to 210°C; a step of forming a perovskite light-absorbing layer on the second electron transport layer; a step of forming a hole transport layer on the perovskite light-absorbing layer; and a step of forming a metal electrode on the hole transport layer.

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