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Dipolar cations confer defect tolerance in wide-bandgap metal halide perovskites.

  • Author(s): Tan, Hairen
  • Che, Fanglin
  • Wei, Mingyang
  • Zhao, Yicheng
  • Saidaminov, Makhsud I
  • Todorović, Petar
  • Broberg, Danny
  • Walters, Grant
  • Tan, Furui
  • Zhuang, Taotao
  • Sun, Bin
  • Liang, Zhiqin
  • Yuan, Haifeng
  • Fron, Eduard
  • Kim, Junghwan
  • Yang, Zhenyu
  • Voznyy, Oleksandr
  • Asta, Mark
  • Sargent, Edward H
  • et al.
Abstract

Efficient wide-bandgap perovskite solar cells (PSCs) enable high-efficiency tandem photovoltaics when combined with crystalline silicon and other low-bandgap absorbers. However, wide-bandgap PSCs today exhibit performance far inferior to that of sub-1.6-eV bandgap PSCs due to their tendency to form a high density of deep traps. Here, we show that healing the deep traps in wide-bandgap perovskites-in effect, increasing the defect tolerance via cation engineering-enables further performance improvements in PSCs. We achieve a stabilized power conversion efficiency of 20.7% for 1.65-eV bandgap PSCs by incorporating dipolar cations, with a high open-circuit voltage of 1.22 V and a fill factor exceeding 80%. We also obtain a stabilized efficiency of 19.1% for 1.74-eV bandgap PSCs with a high open-circuit voltage of 1.25 V. From density functional theory calculations, we find that the presence and reorientation of the dipolar cation in mixed cation-halide perovskites heals the defects that introduce deep trap states.

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