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Nature

  • Perovskite

Regulating surface potential maximizes voltage in all-perovskite tandems

Authors Hao Chen, Aidan Maxwell, Chongwen Li, Sam Teale, Bin Chen, Tong Zhu, Esma Ugur, George Harrison, Luke Grater, Junke Wang, Zaiwei Wang, Lewei Zeng, So Min Park, Lei Chen, Peter Serles, Rasha Abbas Awni, Biwas Subedi, Xiaopeng Zheng, Chuanxiao Xiao, Nikolas J. Podraza, Tobin Filleter, Cheng Liu, Yi Yang, Joseph M. Luther, Stefaan De Wolf, Mercouri G. Kanatzidis, Yanfa Yan & Edward H. Sargent

Abstract

The open circuit voltage (VOC) deficit in perovskite solar cells (PSCs) is greater in wide bandgap (>1.7 eV) cells than in ~1.5 eV perovskites.1,2 Quasi-Fermi level splitting (QFLS) measurements reveal VOC-limiting recombination at the electron transport layer (ETL) contact.3-5 This, we find, stems from inhomogeneous surface potential and poor perovskite-ETL energetic alignment. Common monoammonium surface treatments fail to address this; instead we introduce diammonium molecules to modify the perovskite surface states and achieve a more uniform spatial distribution of surface potential. Using 1,3-propane diammonium (PDA), QFLS increases by 90 meV, enabling 1.79 eV PSCs with a certified 1.33 V VOC, and > 19% power conversion efficiency (PCE). Incorporating this layer into a monolithic all-perovskite tandem, we report a record VOC of 2.19 V (89% of the detailed balance VOC limit) and > 27% PCE (26.3% certified quasi-steady-state). These tandems retain more than 86% of their initial PCE after 500 hrs operation.

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