Influence of Hot Spot Heating on Stability of Large Size Perovskite Solar Module with a Power Conversion Efficiency of ~14% Kunpeng Li, Junyan Xiao, Xinxin Yu, Tongle Bu, Tianhui Li, Xi Deng, Sanwan Liu, Jize wang, zhiliang ku, jie zhong, fuzhi huang, zhicheng zhong, yong peng,, * wei li #, * and Yibing Cheng,# State Key Lab of Advanced Technologies for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China Hubei Key Laboratory of Low Dimensional Optoelectronic Materials and Devices, Hubei University of Arts and Science, Xiangyang 441053, China # Australian Research Council Centre of Excellence in Exciton Science, Monash University, VIC 3800, Australia Corresponding Author *email:yongpeng@whut.edu.cn (Y. Peng), wei.li2@monash.edu (W. Li) S-1
1. Material and methods 1.1. Materials Unless specified otherwise, all chemicals were purchased from either Alfa Aesar or Sigma-Aldrich and used as received. 2,2,7,7 -Tetrakis-(N, N-di-4-methoxyphenylamino)-9,9 -spirobi-fluorenes (Spiro- OMeTAD) was purchased from Shenzhen Feiming Science and Technology Corp. Ltd., and methylammonium iodide (MAI) was purchased from Xi an Polymer Light Technology Corp. 1.2. Preparation of devices Indium tin oxide coated glass (ITO-glass) was patterned by a femtosecond laser, followed by ultrasonic cleaning in detergent water, deionized water and ethanol for 15 min each. The 10 cm 10 cm substrates were then dried under an N 2 flow and cleaned by UVO for 10 min to remove any organic residues. Fullerene C 60 was first thermally evaporated onto the ITO-coated substrates with a thickness of 10 nm under a deposition pressure of 8 10-6 mbar at a deposition rate of 0.1 Å s -1. The 160 nm PbI 2 films were then thermally evaporated on the C 60 underlayer with controlled deposition rates of 20 Å s -1, as monitored by a quartz crystal microbalance sensor S1. After the PbI 2 deposition process, the samples were transferred to a spin coater in an N 2 -filled glovebox for the subsequent chemical conversion steps. A 56 mg ml -1 methyl-ammonium iodide (MAI) solution in ethanol containing 24 µl of 2-methoxyethanol was spread on the whole PbI 2 film and then spin-coated at a rate of 3000 rpm for 30 s. The yellow film turned brown during the spin-coating and was then annealed at 150 C for 10 min in ambient condition. To prepare the hole transporting layer, a solution of Spiro-OMeTAD dissolved in ethyl acetate S2 was dropped onto the perovskite layer while spinning at a rotation rate of 2000 rpm. For the modules, P1 patterning of the module was performed with a femtosecond laser (Wuhan Hongtuo). After the HTM layer was deposited, the C 60 /perovskite/spiro-ometad layers were fully removed to ensure low contact resistance at the interconnected space through P2 patterning. Then, the films were put in ambient air to facilitate the oxidation of Spiro-OMeTAD for six hours (RH<20%). Finally, 60 nm Au or Cu was evaporated through a properly designed mask under high vacuum (4 10-6 mbar) to complete the devices for tests. The devices and modules were measured with metal masks area of 0.16 cm 2 and 31.71 cm 2, respectively. For the sealing procedure, the PSMs and PSCs were encapsulated with a protective glass by sealant (HelioSeal PVS 101) in the N 2 -filled glovebox. 1.3. Materials and Devices Characterization S-2
The photocurrent density-voltage characteristics of the devices were measured with a scan rate of 0.01 V s -1 and perovskite solar modules were measured with a scan rate of 0.1 V s -1 under standard simulated AM 1.5 G illumination (100 mw cm -1 ) using a solar simulator (Oriel 94023A, 300 W), which was calibrated using a standard Si solar cell (Oriel, VLSI standards). The morphologies and microstructures of the deposited PbI 2 films and perovskite films were investigated using a field-emission scanning electron microscope (FE-SEM, Zeiss Ultra Plus) and an X-ray diffractometer (XRD, D8 Advance). X-ray photoelectron spectroscopy (XPS) was implemented on a surface analysis system (ESCALAB 250Xi, Thermo Fisher scientific) with Al Kα radiation (1486.6 ev), analyzing the surface nature and concentration of the active surface. To measure the inner layers, ion beam sputtering technique was used to remove the surface part. The temperature of hot spot heating area in PSMs was recorded by an infrared camera (FLUKE Ti400) when the PSM was applied with a voltage bias of 14.0 V. Sun light illuminating was not applied during testing to avoid possible perovskite thermal decomposition at an extended sun light exposure. Furthermore, the long-term stability measurements were carried out on performing PSMs and PSCs with encapsulation. The devices were measured in the ambient conditions and the cells were kept in N 2 -filled glovebox at open-circuit condition after each measurement. S-3
Figure S1. Images of PbI 2 and CH 3 NH 3 PbI 3 films. SEM images of (a) Surface image of the perovskite film. (b) Cross-section image of the perovskite layer. Both the scale bars indicate 1 µm. Optic photo of perovskite film and PbI 2 film (c) CH 3 NH 3 PbI 3 film; (d) PbI 2 film. S-4
Figure S2. the certified data of the perovskite solar module under reverse scan. S-5
Figure S3. The certified data of the perovskite solar module under forward scan Table S1 the photovoltaic parameters of PSCs and PSMs. Statistical analysis was carried out for 60 devices fabricated for the PSCs and 35 devices for the PSMs Device (V) J sc (ma cm -2 ) FF PCE (%) Cell (0.16 cm 2 ) Module (31.71 cm 2 ) 0.98±0.01 (0.99) 13.71±0.38 (14.10) a J sc for the module (=I sc /31.71 14) 19.1±1.0 (20.1) 17.9±0.6 a (18.6) S-6 0.74±0.02 (0.76) 0.65±0.05 (0.74) 13.87±1.25 (15.11) 11.17±2.31 (13.98)
(a) (b) 80 60 Reverse scan Forward scan Current (ma) 40 20 RS FS (V) 14.22 14.03 I sc (ma) 63.7 63.7 FF 0.660 0.655 PCE (%) 12.20 11.95 Active area: 49 cm 2 0 0 2 4 6 8 10 12 14 Voltage (V) Figure S4. (a) the photo of a PSM. (b) I-V curve of a PSM based on Au electrode. The PSM was measured with a calculated area of 49 cm 2 under the AM1.5G (100 mw cm -2 ). (a) 24 Current density (ma cm -2 ) 20 16 12 8 4 PSC-Cu RS FS (V) 953 950 J sc (ma cm -2 ) 18.5 18.7 FF 0.74 0.73 PCE (%) 13.05 13.00 Reverse scan Forward scan 0 0.0 0.2 0.4 0.6 0.8 1.0 Voltage (V) (b) 50 Current (ma) 40 30 20 10 PSM-Cu RS FS (V) 13.65 13.58 I sc (ma) 39.63 40.91 FF 0.65 0.61 PCE (%) 11.09 10.69 Reverse scan Forward scan 0 0 2 4 6 8 10 12 14 Voltage (V) Figure S5. (a) the J-V curve of a 0.16 cm 2 PSC based on Cu electrode (100 mw cm -2 ). (b) I-V curve of a PSM based on Cu electrode.the PSM was measured with a metal mask area of 31.71 cm 2 under the AM1.5 G (100 mw cm -2 ). (a) Nomalized parameters 1.2 1.0 0.8 0.6 0.4 0.2 0.0 PSM-A1 J sc FF 0 2 4 6 8 10 12 14 16 Time (days) (b) Normalized parameters 1.2 1.0 0.8 0.6 0.4 0.2 0.0 PSM-C1 0 5 10 15 20 25 30 Time (days) Figure S6 The photovoltaic parameters evoltution of PSMs based on (a) Au and (b) Cu. J sc FF S-7
Figure S7.Infrared images of the PSMs (a) PSM with Au electrode (b) PSM with Cu electrode. Both the PSMs were recorded the surface temperature as a function of 100 s at a bias of 14.0 V without sunlight. The room temperature is about 25 o C. S-8
Figure S8. Shunt resistance of PSM using Au and Cu electrode as a function of time. Both the encapsulated PSMs were stored in dry glovebox. REFERENCES S1 S2 Li, K.; Xiao, J.; Yu, X.; Li, T.; Xiao, D.; He, J.; Zhou, P.; Zhang, Y.; Li, W.; Ku, Z.; Zhong, J.; Huang, F.; Peng, Y. & Cheng, Y-B. An Efficient, Flexible Perovskite Solar Module Exceeding 8% Prepared with an Ultrafast PbI 2 Deposition Rate. Sci. Rep. 2018, 8, 442. Bu, T.; Wu, L.; Liu, X.; Yang, X.; Zhou, P.; Yu, X.; Qin, T.; Shi, J.; Wang, S.; Li, S.; Ku, Z.; Peng, Y.; Huang, F.; Meng, Q. B.; Cheng, Y-B.; Zhong, J. Synergic Interface Optimization with Green Solvent Engineering in Mixed Perovskite Solar Cells. Adv. Energy Mater. 2017, 7, 1700576. S-9