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7209366 
Journal Article 
New-type highly stable 2D/3D perovskite materials: the effect of introducing ammonium cation on performance of perovskite solar cells 
Zheng, H; Dai, S; Zhou, K; Liu, G; Zhang, B; Alsaedi, A; Hayat, T; Pan, Xu; , 
2019 
SCIENCE PRESS 
BEIJING 
508-518 
WOS:000462512200006 
Perovskite solar cells (PSCs) have drawn wide attention due to the rapidly rising efficiency which presently attains over 23%. However, problems of instability continue to plague the high-efficiency devices impairing their practical applications. Here, by firstly introducing smaller-size NH4+ into (FAPbI(3))(0.85)(MAPbBr(3))(0.15) (FA/MA) to form a novel 2D-3D mixed structure, we designed and prepared new-type hybrid perovskite materials of [(NH4)(2.4)(FA)(n-1)PbnI3n+1.4](0.85) (MAPbBr(3))(0.15) (n=3, 5, 7, 9 and 11) (A/FA/MA) and used them as absorber in solar cells. Especially, unlike the reported 2D/MD perovskite perovskites based on larger-size ammonium salts; A/FA/MA perovskites are the first to display red-shift light absorption and decreased band gaps in comparison to normal perovskites. Consequently, when n=9, the A/FA/MA device shows outstanding performance with a solar to electric power conversion efficiency (PCE) of 18.25% and negligible hysteresis. When the encapsulated A/FA/MA perovskite device was soaked in full sunlight for 1,000 h, the PCE remains almost unchanged. Moreover, the unsealed A/FA/MA PSCs maintain 90% of their initial PCE when aged at high humidity conditions over the same 1000-h time period. Our findings provide a guide for the future development of such novel perovskites and it is helpful to select more suitable ammonium salt to obtain highly efficient and stable 2D-3D PSCs.