Structurally Reinforced All‐Inorganic CsPbI<sub>2</sub>Br Perovskite by Nonionic Polymer via Coordination and Hydrogen Bonds
Huirong Peng, Molang Cai, Jiyu Zhou, Yi Yang, Xihong Ding, Tao Ye, Gao Wu, Xuepeng Liu, Jia Hong Pan, Songyuan Dai
Abstract
The all‐inorganic CsPbI 2 Br perovskite with superior thermal durability faces challenges of low‐phase stability and high moisture sensitivity. Herein, a nonionic additive of polyethyleneimine (PEI) with multiple amino groups is introduced to form hydrogen bond with I − /Br − ions and coordinate with Pb 2+ /Cs + ions simultaneously. The strong interplay between PEI and CsPbI 2 Br achieves a well‐controlled grain size, reduced defects, and reinforced phase structure of CsPbI 2 Br film, which boosts the power conversion efficiency (PCE) of perovskite solar cells to 15.48%. The hydrophobic long alkyl chain of PEI greatly improves the humidity resistance, retaining 81.9% of initial PCE of zjr unsealed device under 20 ± 5% relative humidity (RH) for 500 h. Remarkably, a PCE of 13.37% is achieved by the device based on CsPbI 2 Br–PEI film processed under ambient condition (≈22% RH, ≈25 °C).