3. S INGLE CELL FOR TANDEM SOLAR CELL : PEROVSKITE TOP CELLS AND SILICON
3.5. R EFERENCES
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13. Zheng, J.; Lau, C. F. J.; Mehrvarz, H.; Ma, F.-J.; Jiang, Y.; Deng, X.; Soeriyadi, A.; Kim, J.; Zhang, M.; Hu, L.; Cui, X.; Lee, D. S.; Bing, J.; Cho, Y.; Chen, C.; Green, M. A.; Huang, S.; Ho-Baillie, A. W. Y., Large area efficient interface layer free monolithic perovskite/homo-junction-silicon tandem solar cell with over 20% efficiency. Energy & Environmental Science 2018, 11 (9), 2432-2443.
14. Mazzarella, L.; Lin, Y.-H.; Kirner, S.; Morales-Vilches, A. B.; Korte, L.; Albrecht, S.; Crossland, E.; Stannowski, B.; Case, C.; Snaith, H. J.; Schlatmann, R., Infrared Light Management Using a Nanocrystalline Silicon Oxide Interlayer in Monolithic Perovskite/Silicon Heterojunction Tandem Solar Cells with Efficiency above 25%. Advanced Energy Materials 2019, 9 (14), 1803241.
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25. Saliba, M.; Matsui, T.; Seo, J.-Y.; Domanski, K.; Correa-Baena, J.-P.; Nazeeruddin, M. K.; Zakeeruddin, S. M.; Tress, W.; Abate, A.; Hagfeldt, A., Cesium-containing triple cation perovskite solar cells: improved stability, reproducibility and high efficiency. Energy & environmental science 2016, 9 (6), 1989-1997.
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Bolink, H. J., Trap-Assisted Non-Radiative Recombination in Organic–Inorganic Perovskite Solar Cells. Advanced Materials 2015, 27 (11), 1837-1841.
27. Wang, Q.; Dong, Q.; Li, T.; Gruverman, A.; Huang, J., Thin Insulating Tunneling Contacts for Efficient and Water-Resistant Perovskite Solar Cells. Advanced Materials 2016, 28 (31), 6734-6739.
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31. Jin, T.-Y.; Li, W.; Li, Y.-Q.; Luo, Y.-X.; Shen, Y.; Cheng, L.-P.; Tang, J.-X., High- Performance Flexible Perovskite Solar Cells Enabled by Low-Temperature ALD-Assisted Surface Passivation. Advanced Optical Materials 2018, 6 (24), 1801153.
32. Mali, S. S.; Shim, C. S.; Park, H. K.; Heo, J.; Patil, P. S.; Hong, C. K., Ultrathin Atomic Layer Deposited TiO2 for Surface Passivation of Hydrothermally Grown 1D TiO2 Nanorod Arrays for Efficient Solid-State Perovskite Solar Cells. Chemistry of Materials 2015, 27 (5), 1541-1551.
33. Peng, J.; Khan, J. I.; Liu, W.; Ugur, E.; Duong, T.; Wu, Y.; Shen, H.; Wang, K.;
Dang, H.; Aydin, E.; Yang, X.; Wan, Y.; Weber, K. J.; Catchpole, K. R.; Laquai, F.; De Wolf, S.; White, T. P., A Universal Double-Side Passivation for High Open-Circuit Voltage in Perovskite Solar Cells: Role of Carbonyl Groups in Poly(methyl methacrylate). Advanced Energy Materials 2018, 8 (30), 1801208.
34. Shao, Y.; Xiao, Z.; Bi, C.; Yuan, Y.; Huang, J., Origin and elimination of photocurrent hysteresis by fullerene passivation in CH3NH3PbI3 planar heterojunction solar cells. Nature Communications 2014, 5 (1), 5784.
35. Li, X.; Chen, C.-C.; Cai, M.; Hua, X.; Xie, F.; Liu, X.; Hua, J.; Long, Y.-T.;
Tian, H.; Han, L., Efficient Passivation of Hybrid Perovskite Solar Cells Using Organic Dyes with COOH Functional Group. Advanced Energy Materials 2018, 8 (20), 1800715.
36. Kim, M.; Motti, S. G.; Sorrentino, R.; Petrozza, A., Enhanced solar cell stability by hygroscopic polymer passivation of metal halide perovskite thin film. Energy & Environmental Science 2018, 11 (9), 2609-2619.
37. Cho, Y.; Soufiani, A. M.; Yun, J. S.; Kim, J.; Lee, D. S.; Seidel, J.; Deng, X.;
Green, M. A.; Huang, S.; Ho-Baillie, A. W. Y., Mixed 3D–2D Passivation Treatment for Mixed- Cation Lead Mixed-Halide Perovskite Solar Cells for Higher Efficiency and Better Stability. Advanced Energy Materials 2018, 8 (20), 1703392.
38. Zheng, X.; Chen, B.; Dai, J.; Fang, Y.; Bai, Y.; Lin, Y.; Wei, H.; Zeng, Xiao C.;
Huang, J., Defect passivation in hybrid perovskite solar cells using quaternary ammonium halide anions and cations. Nature Energy 2017, 2 (7), 17102.
39. Zhao, P.; Liu, Z.; Lin, Z.; Chen, D.; Su, J.; Zhang, C.; Zhang, J.; Chang, J.; Hao, Y., Device simulation of inverted CH3NH3PbI3−xClx perovskite solar cells based on PCBM electron transport layer and NiO hole transport layer. Solar Energy 2018, 169, 11-18.
40. Zheng, Y.; Kong, J.; Huang, D.; Shi, W.; McMillon-Brown, L.; Katz, H. E.; Yu, J.;
Taylor, A. D., Spray coating of the PCBM electron transport layer significantly improves the efficiency of pin planar perovskite solar cells. Nanoscale 2018, 10 (24), 11342-11348.
41. Anti-Reflection Coatings. In PVEducation. Available at:
https://www.pveducation.org/pvcdrom/design-of-silicon-cells/anti-reflection-coatings
Figure 3.1. (a) Schematic of the PVK top cell for the tandem SC. Various techniques for the employing the PVK SC as a tandem SC, such as (b) band gap tuning, optimizing band alignment, Copyright 2019 Elsevier Ltd.12 and (c) 3D/2D PVK.
Figure 3.2. Absorption coefficient spectra of the (a) (MAPbI3)1-x(MAPbBr3)x PVK films showing extrapolated energy band gaps ranging from 1.5 eV to 2.0 eV. J-V curves of monolithic tandem devices with (b) (MAPbI3)1-x(MAPbBr3)x PVK films on PEDOT:PSS. Copyright 2019 Elsevier Ltd.12
Table 3.1. Summary of the device performance of PVK/Si tandem devices with (MAPbI3)1- x(MAPbBr3)x PVK films using different doping ratios on PEDOT:PSS. Copyright 2019 Elsevier Ltd.12
Figure 3.3. SEM image of (MAPbI3)1-x(MAPbBr3)x PVK films showing extrapolated energy band gaps ranging from 1.5 eV to 2.0 eV. Copyright 2019 Elsevier Ltd.12
Figure 3.4. Absorption coefficient spectra of the (a) (FAPbI3)1-x(MAPbBr3)x PVK films showing extrapolated energy band gaps ranging from 1.5 eV to 2.0 eV. J-V curves of monolithic tandem devices with (b) (FAPbI3)1-x(MAPbBr3)x PVK films on PEDOT:PSS. Copyright 2019 Elsevier Ltd.12
Table 3.2. Summary of the device performance of PVK/Si tandem devices with (FAPbI3)1-x(MAPbBr3)x
PVK films using different doping ratios on PEDOT:PSS. Copyright 2019 Elsevier Ltd.12
Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
x = 0.05 13.27 1.230 20.30 3.31
x = 0.10 14.12 1.430 71.14 14.36
x = 0.15 14.66 1.445 69.01 14.62
x = 0.20 15.12 1.470 76.68 17.04
x = 0.25 15.21 1.490 75.50 17.11
x = 0.30 14.79 1.510 61.59 13.75
Figure 3.5. SEM image of (FAPbI3)1-x(MAPbBr3)x PVK films showing extrapolated energy band gaps ranging from 1.5 eV to 2.0 eV. Copyright 2019 Elsevier Ltd.12
Figure 3.6. (a) Relative energy levels of the various device components in the PVK SCs. J-V curves of the PVK SCs with (b) various HTLs using (FAMAPbI3)0.8(MAPbBr3)0.2 PVK films. Copyright 2019 Elsevier Ltd.12
Table 3.3. Summary of the device performance of PVK SCs with (FAPbI3)0.8(MAPbBr3)0.2 PVK films deposited on different HTLs. Copyright 2019 Elsevier Ltd.12
Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
PEDOT:PSS 18.675 0.84 69.63 10.92
PEDOT:GO 19.425 0.91 79.10 13.98
NiOx 20.930 1.08 73.14 16.54
PTAA 21.150 1.14 77.49 18.68
Figure 3.7. (a) J-V curves of the PVK SCs with different doping ratios of (FAMAPbI3)1-x(MAPbBr3)x
PVK films with poly(triaryl amine) (PTAA). (d) J-V curves of monolithic tandem devices with different doping ratios of (FAMAPbI3)1-x(MAPbBr3)x PVK films prepared on PTAA. Copyright 2019 Elsevier Ltd.12
Table 3.4. Summary of the device performance of PVK SCs with (FAPbI3)1-x(MAPbBr3)x PVK films using different doping ratios deposited on poly(triaryl amine) (PTAA). Copyright 2019 Elsevier Ltd.12
Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
x = 0.15 22.21 1.10 73.53 17.96
x = 0.20 21.15 1.14 77.49 18.68
x = 0.25 20.41 1.16 76.48 18.11
x = 0.30 19.55 1.19 61.75 14.36
Table 3.5. Summary of the device performance of PVK/Si tandem devices with (FAPbI3)1-x(MAPbBr3)x
PVK films using different doping ratios deposited on poly(triaryl amine) (PTAA). Copyright 2019 Elsevier Ltd.12
Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
x = 0.15 14.38 1.62 70.18 16.35
x = 0.20 14.91 1.65 76.91 18.92
x = 0.25 14.72 1.67 73.93 18.18
x = 0.30 14.76 1.69 65.50 16.34
Figure 3.8. Absorption coefficient spectra of the (a) Cs0.05FA0.80MA0.15Pb(I1-xBrx)3 PVK films showing extrapolated energy band gaps of 1.65 eV (Br 20%), 1.68 eV (Br 25%) and 1.71 eV (Br 30%). (b) J-V curves of the PVK SCs based on Cs0.05FA0.80MA0.15Pb(I1-xBrx)3 as function of band gap.
Table 3.6. Summary of the device performance of Cs0.05FA0.80MA0.15Pb(I1-xBrx)3 PVK SC as function of band gap.
Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
Br 20% 19.85 1.11 73.1 16.11
Br 25% 19.22 1.13 73.34 15.93
Br 30% 18.36 1.15 72.97 15.34
Figure 3.9. SEM image of Cs0.05FA0.80MA0.15Pb(I1-xBrx)3 PVK films with band gaps of 1.65 eV (Br 20%), 1.68 eV (Br 25%) and 1.71 eV (Br 30%).
Figure 3.10. Absorption coefficient spectra of the (a) Cs0.05FA0.80MA0.15Pb(I1-xBrx)3 PVK films with different concentrations of MACl : 5, 10, and 20 mg/mL. (b) J–V curves of the PVK SCs based on Cs0.05FA0.80MA0.15Pb(I1-xBrx)3 with different MACl concentrations: 5, 10, and 20 mg/mL.
Table 3.7. Summary of the device performance of the PVK SCs based on Cs0.05FA0.80MA0.15Pb(I1-xBrx)3
with different MACl concentrations: 5, 10, and 20 mg/mL.
Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
Without MACl 19.85 1.11 73.1 16.11
5 mg/mL 20.15 1.12 78.64 17.75
10 mg/mL 20.2 1.14 78.90 18.17
20 mg/mL 19.9 1.13 76.83 17.28
Figure 3.11. XRD pattern of the (a) Cs0.05FA0.80MA0.15Pb(I1-xBrx)3 PVK films with different MACl concentrations: 5, 10, and 20 mg/mL. (b) XRD peaks (110) of PVK film with different MACl concentrations, exhibiting shifts in the peaks.
Figure 3.12. (a) Reciprocal FWHM obtained from films prepared with different additive concentrations at the diffraction peak of 14.1° for the α-phase PVK. Top view of SEM images of devices prepared with different MACl concentrations: (b) 0 mg/mL, (c) 5 mg/mL, (d) 10 mg/mL, and (e) 20 mg/mL.
Figure 3.13. Schematic representations of the 2D‐RP PVK and relevant spacing.
Figure 3.14. (a) Absorption coefficient spectra and (b) J–V curves of the 3D/2D PVK SCs with different BABr concentrations: 0.5, 1, and 2 mg/mL.
Table 3.8. Summary of the device performance of the 3D/2D PVK SCs with different BABr concentrations: 0.5, 1, and 2 mg/mL.
Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
3D Ref. 20.2 1.14 78.90 18.17
0.5 mg/mL 20.13 1.15 78.88 18.26
1 mg/mL 20.18 1.17 79.43 18.75
2 mg/mL 18.27 1.12 66.39 13.58
Figure 3.15. XRD pattern of the (a) Cs0.05FA0.80MA0.15Pb(I0.8Br0.2)3 PVK films with different amounts of BABr : 0.5, 1, and 2 mg/mL.(b) Extended XRD showing similar peaks for samples with thicker 2D‐
RP interlayers.
Figure 3.16. PL spectroscopy. (a) PL spectra (excitation wavelength = 540 nm) and (b) TRPL measurements of the 2D/3D PVK heterostructures processed through the deposition of different concentrations of BABr (0.5, 1, and 2 mg/mL) on top of Cs0.05FA0.80MA0.15Pb(I0.8Br0.2)3 PVK films.
Figure 3.17. SEM images of (a) Cs0.05FA0.80MA0.15Pb(I0.8Br0.2)3 PVK films, (b–d) the 2D/3D PVK heterostructures processed by the deposition of different concentrations of 0.5, 1, and 2 mg/mL on top of Cs0.05FA0.80MA0.15Pb(I0.8Br0.2)3 PVK films.
Figure 3.18. Molecular structure of (a) PCBM and (b) F8TBT.
Figure 3.19. J–V curve of the PVK SCs with different PCBM concentrations: 20 mg/mL, 10 mg/mL, and 10 mg/mL (added F8TBT 2.2 mg).
Table 3.9. Summary of the device performance of the PVK SCs with different PCBM concentrations:
20 mg/mL, 10 mg/mL, and 10 mg/mL (added F8TBT).
Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
PCBM 10 mg 20.01 1.16 72.2 16.76
PCBM 20 mg 20.18 1.17 79.43 18.75
PCBM:F8TBT
(10 mg : 2.0 mg) 20.16 1.16 78.71 18.41
PCBM:F8TBT
(10 mg : 2.2 mg) 20.21 1.18 79.63 18.99
PCBM:F8TBT
(10 mg : 2.5 mg) 20.31 1.17 78.97 18.77
Figure 3.20. SEM image of ETL with different PCBM concentrations : 20 mg/mL, 10 mg/mL, and 10 mg/mL (added F8TBT 2.2 mg).
Figure 3.21. (a) Schematic structure of semi-transparent PVK SC. (b) J–V curve of the semi-transparent PVK SCs according to illumination side.
Table 3.10. Summary of the device performance of the PVK SCs with different PCBM concentrations:
20 mg/mL and 10 mg/mL (added F8TBT 2.2 mg).
Opaque Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
PCBM 20 mg 20.18 1.17 79.43 18.75
PCBM:F8TBT
(10 mg : 2.2 mg) 20.21 1.18 79.63 18.99
Table 3.11. Summary of the device performance of the semi-transparent PVK SCs with different PCBM concentrations: 20 mg/mL and 10 mg/mL (added F8TBT 2.2 mg).
Top-illumination
Semi-transparent Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
PCBM 20 mg 16.52 1.16 78.69 15.08
PCBM:F8TBT
(10 mg : 2.2 mg) 17.13 1.17 78.97 15.83
Figure 3.22. Transmittance and absorbance data of ETL with different PCBM concentrations: 20 mg/mL, 10 mg/mL, and 10 mg/mL (added F8TBT 2.2 mg).
Figure 3.23. (a) Schematic of Si bottom cell for the tandem SC. Various techniques for employing the PVK SC in the tandem SC, such as (b) emitter doping, (c) back side texturing, and (d) refractive index control for maximizing long-wavelength absorption.
Figure 3.24. (a) Schematic of emitter doping process. (b) Sheet resistance of an emitter as a function of doping temperature.
Figure 3.25. (a) J–V curve and (b) EQE of the Si SC as a function of doping temperature.
Table 3.12. Summary of the Si SC as a function of doping temperature.
2 min Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
800 ℃ 22.96 0.562 69.37 8.95
850 ℃ 23.61 0.571 73.89 9.97
900 ℃ 22.12 0.572 70.72 8.95
950 ℃ 18.66 0.536 73.86 7.39
Figure 3.26. (a) Schematic of Si SC with a textured back surface. (b) J–V curve and (c–d) EQE of the Si SCs compared with a double-side polished Si SC with a Si SC featuring a textured back surface.
Table 3.13. Summary of the Si SC compared with a double-side polished Si SC Si SC featuring a textured back surface.
850 ℃, 2 min Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
DSP Si SC 23.61 0.571 73.89 9.97
BST Si SC 23.94 0.571 73.69 10.07
Figure 3.27. (a) Strategy to minimize long-wavelength reflectance by using graded refractive index matching and (b) maximize long-wavelength absorption of bottom Si SC for the tandem SC.
Figure 3.28. (a) Schematic of local contact design and (b–f) OM image of local contact metal electrode design on a SiNx layer with different contact area ratios: 0.5, 1, 3, 5, and 10 %.
Figure 3.29. (a) J–V curve of the Si SCs with local contact metal electrode design on a SiNx layer according to different contact area ratios: 0.5, 1, 3, 5, and 10 % and (b) EQE with local contact metal electrode design on a SiNx layer.
Table 3.14. Summary of the Si SC with a local contact metal electrode design on a SiNx layer according to different contact area ratios: 0.5, 1, 3, 5, and 10%
Shading area Jsc (mA/cm2) Voc (V) FF (%) Efficiency (%)
Ref. 23.94 0.571 73.69 10.07
0.5 % 29.67 0.607 54.84 9.88
1 % 29.52 0.607 73.48 13.17
3 % 28.83 0.604 73.21 12.75
5 % 28.21 0.605 73.39 12.53
10 % 26.74 0.602 72.29 11.64
Figure 3.30. (a) Photoconductance and (b) lifetime of the Si wafer without a SiNx layer and with a SiNx layer.
Table 3.15. Summary of lifetime of the Si wafer without a SiNx layer and with a SiNx layer.
Bare Si wafer R.I. 2.84 Si wafer Photoconductance at 0.005 S (Siemens) 1.43E-3 3.57E-3
Lifetime at Spec. MCD (s) 9.0E-6 1.54E-5
4
M ONOLITHIC P EROVSKITE /S ILICON T ANDEM S OLAR
C ELL
4.1.INTRODUCTION
Recently, the maximum efficiency of monolithic PVK/Si tandem SCs was reported as 29.5% in Oxford Photovoltaics.1 This is significant, as the result exceeds the theoretical limiting efficiency of 29.43% of the reevaluated Si SC.2 Considerable research has been conducted to develop high-efficiency monolithic PVK/Si tandem SCs.3-12 Among the research about PVK/Si tandem SCs, pin-structured PVK SCs have been used to maximize light absorption based on SHJ SCs for high-efficiency tandem cells.
3-8, 13, 14 As discussed in the previous chapter, when the SHJ cell is used, the advantage of high efficiency can be utilized; however, the potential for commercialization is very low owing to high costs. To overcome the shortcomings of such a SHJ-cell-based tandem SC, an ultra-high-efficiency tandem SC can be developed that can offer a lower levelized cost of energy than existing commercial Si PERC SCs.
Therefore, studies on ultra-high efficiency tandem SCs based on the SHJ cell are being conducted.3-5, 15 However, the Si SC that currently occupies the mainstream of the SC market is not a SHJ cell but rather a p-Si homojunction SC.16-20 Taking advantage of the high market share of p-Si homojunction SCs in the SC market, high-efficiency tandem SCs can be fabricated by introducing additional PVK and tandem process lines without major changes to the infrastructure of the current SC industry, facilitating increases in market share and leadership. Therefore, there is a need for research on the p- type-based homojunction SC. However, owing to the current trend of high-efficiency studies of tandem SCs, n-Si wafers, which are relatively more efficient than p-Si wafers, have been introduced in tandem homojunction-based SCs.12, 21-23 Yet, as p-Si wafers have superior advantages over n-Si wafers in terms of yield in the commercialization process, p-Si-based homojunction SCs maintain the bulk of the SC market.16, 24 Furthermore, the problem of long-wavelength absorption of the HTL that occurs in n-i-p structured PVK SCs is a limiting factor.9, 25, 26 Therefore, the efficiency potential is limited; consequently, an HTL minimizing long-wavelength absorption must be developed or a p-i-n structured PVK SC must be introduced. For the HTL, development should be based on novel polymeric or inorganic-based materials.27 Although substantial research has been performed on this topic, it is expected that a considerable amount of time will be needed to improve efficiency. Meanwhile, a p-i-n structured PVK
SC can be applied immediately because it has already been sufficiently studied.28 However, the p-i-n structured PVK SC is not structurally suitable for tandemization with the n-Si homojunction SC and can be applied only to the p-Si homojunction SC. Therefore, research on Si/PVK tandem SCs based on p-Si homojunction SCs, which demonstrate the above-mentioned advantages, is required.
In this chapter, we present PVK/Si tandem SCs, based on a p-Si homojunction SC, with the single cell for tandem SC discussed in the previous chapter. First, we discuss a current matching method for optimizing the current density of tandem SCs. Then, we present the optimized conditions based on the sputtering temperature and pressure conditions of the ITO layer, applied to drive the tandem SC through recombination. Next, we implement an optically designed tandem SC based on an Al-BSF Si SC with a tandem SC that minimizes light loss through the application of graded refractive index matching technology. Further, long-term stability is examined through tests such as the light soaking test, thermal stress test, and damp heat test of tandem SCs, as glass encapsulation technology is introduced. Finally, a tandem SC based on a PERC Si SC is fabricated from p-Si homojunction SCs, which occupy the mainstream of the Si SC market.
4.2.EXPERIMENTAL METHODS
4.2.1. Experimental Details of Monolithic Perovskite/Silicon Tandem Solar Cell
Monocrystalline Si wafers (1–5 Ω cm, p-type, CZ, 525 µm) with a textured back-side were cleaned using the RCA cleaning procedure, and oxide was removed using a buffered oxide etchant solution. The phosphorus SOD (Filmtronics SOD P507) was spin-coated onto the c-Si wafers, while on the other side, Al (2 µm) was evaporated. During heat treatment at 850 °C for 2 min using a RTA system to control the doping level, the n+ emitter was formed with a sheet resistance of 100 Ω/sq on the front side, and p+ Al-BSF was formed on the rear side of the Si wafers. The residual phosphorous silicate glass was removed by hydrogen fluoride. Subsequently, the Ag-metal back electrodes (1 µm) were deposited by e-beam evaporation. Finally, an ITO recombination layer was grown on the top surface using an RF magnetron sputter at 250° and 7 mTorr with a sputtering power of 120 W. The PVK SCs were fabricated in a standard arrangement of ITO/PTAA/PVK/PC60BM/ZnO/Ag. HTLs, such as PTAA (Sigma-Aldrich, 2 mg/ml in chlorobenzene (CB)), were spin-coated onto the ITO of the Si bottom cell with UV treatment at 4000 rpm and annealed at 100 °C for 10 min. In the case of Br 25%, the PVK precursor solution of Cs0.05FA0.80MA0.15Pb(I0.75Br0.25)3 was prepared by dissolving 0.07 mmol CsI (TCI), 0.28 mmol MABr (great cell), 1.05 mmol FAI (great cell), 1.10 mmol PbI2 (TCI), and 0.392 mmol PbBr2
(TCI)in DMF/DMSO (4:1 v/v). MACl at 10 mg/mL was added to the PVK precursor solution. The PVK solution was spin-coated in a one-step program at 5000 rpm at ramping times of 1.7 and 30 s.
During this period, 300 μL of ethyl acetate was poured onto the spinning substrate 20 s prior to the end of the program. The substrates were then annealed at 100 °C for 1 h in a nitrogen-filled glove box.