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7226411 
Journal Article 
Introduction of Hydrophobic Ammonium Salts with Halogen Functional Groups for High-Efficiency and Stable 2D/3D Perovskite Solar Cells 
Liu, G; Zheng, H; Xu, X; Xu, S; Zhang, X; Pan, Xu; Dai, S; , 
2019 
Yes 
Advanced Functional Materials
ISSN: 1616-301X
EISSN: 1616-3028 
WILEY-V C H VERLAG GMBH 
WEINHEIM 
WOS:000498650500006 
2D perovskites have attracted extensive attention due to their excellent stability compared with 3D perovskites. However, the intrinsic hydrophilicity of introduced alkylammonium salts effects the humidity stability of 2D/3D perovskites. Devices based on longer chain alkylammonium salts show improvement in hydrophobicity but lower efficiency due to the poorer charge transport among various layers. To solve this issue, two hydrophobic short-chain alkylammonium salts with halogen functional groups (2-chloroethylamine, CEA(+) and 2-bromoethylamine, BEA(+)) are introduced into (Cs(0.1)FA(0.9))Pb(I0.9Br0.1)(3) 3D perovskites to form 2D/3D perovskite structure, which achieve high-quality perovskite films with better crystallization and morphology. The optimal 2D/3D perovskite solar cells (PSCs) with 5% CEA(+) display a power conversion efficiency (PCE) as high as 20.08% under 1 sun irradiation. Because of the notable hydrophobicity of alkylammonium cations with halogen functional groups and the formed 2D/3D perovskite structure, the optimal PSCs exhibit superior moisture resistance and retain 92% initial PCE after aging at 50 +/- 5% relative humidity for 2400 h. This work opens up a new direction for the design of new-type 2D/3D PSCs with improved performance by employing proper alkylammonium salts with different functional groups.