Journal Article

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

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

2018

Overview

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. The performance of wide-bandgap perovskite photovoltaics is limited by the undesired phase transition and high density of deep level traps. Here, Tan et al. incorporate dipolar methylammonium cation to make the material defect-tolerant and achieve a high power conversion efficiency of 20.7%.

• Publisher: Nature Publishing Group UK,Nature Publishing Group,Nature Portfolio
• Subject: 119/118 / 639/301/299/946 / 639/4077/4072/4062 / Cations / Crystal defects / Density functional theory / devices for energy harvesting / Efficiency / Energy conversion efficiency / Humanities and Social Sciences / MATERIALS SCIENCE / multidisciplinary / Open circuit voltage / Perovskites / Photovoltaic cells / Photovoltaics / Science / Science (multidisciplinary) / Solar cells / Traps / Voltage