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Large-Area 23%-Efficient Monolithic Perovskite/Homojunction-Silicon Tandem Solar Cell with Enhanced UV Stability Using Down-Shifting Material

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journal contribution
posted on 11.10.2019, 13:37 by Jianghui Zheng, Hamid Mehrvarz, Chwenhaw Liao, Jueming Bing, Xin Cui, Yang Li, Vinicius R. Gonçales, Cho Fai Jonathan Lau, Da Seul Lee, Yong Li, Meng Zhang, Jincheol Kim, Yongyoon Cho, Laura Granados Caro, Shi Tang, Chao Chen, Shujuan Huang, Anita W. Y. Ho-Baillie
UV-induced degradation and parasitic ultraviolet (UV) absorption by the “sun-facing” carrier transport layer in a perovskite cell hinders stability and electrical performance when the perovskite cell is a top cell for a Si-based tandem. In this work, we tackle these issues by applying textured polydimethylsiloxane (PDMS) films that incorporate a down-shifting material (Ba,Sr)2SiO4:Eu2+ micron phosphor on the front of monolithic perovskite/silicon tandem cells. This film serves multiple purposes: antireflective control for the top cell, light trapping in the Si cell, as well as absorbing UV and re-emitting green light with high quantum yield. When applied onto a 4 cm2 monolithic perovskite/silicon tandem solar cell, the power conversion efficiency was improved from 20.1% (baseline device without any antireflective film) to 22.3% (device with an antireflective film but without the phosphors) and to 23.1% (device with down-shifting phosphor-incorprated antireflective film). The steady-state efficiency of 23.0% and a high fill factor (FF) of 81% achieved by the champion device are the highest values to date for a monolithic perovskite/silicon tandem that uses a homojunction silicon bottom cell. Moreover, results of a continuous UV irradiation test show that this composite down-shifting antireflection film significantly enhances the UV stability for the tandem device. This work demonstrates an elegant approach for improving the efficiency and stability for larger-area perovskite/silicon tandems.