High-Performance Lead-Free Solar Cells Based on Tin-Halide Perovskite Thin Films Functionalized by a Divalent Organic Cation
Min Chen, Qingshun Dong, Felix T. Eickemeyer, Yuhang Liu, Zhenghong Dai, Alexander D. Carl, Behzad Bahrami, Ashraful Haider Chowdhury, Ronald L. Grimm, Yantao Shi, Qiquan Qiao, Shaik M. Zakeeruddin, Michaël Grätzel, Nitin P. Padture
Abstract
Tin-based halide perovskite solar cells (PSCs) hold the most promise among lead-free PSCs, but they are plagued with inadequate environmental stability and power-conversion efficiency (PCE). Here we demonstrate that the optimum incorporation of a bulky divalent organic cation, 4-(aminomethyl)piperidinium (4AMP), in FASnI3 thin films improves stability, optoelectronic properties, and PSC performance. The optimized PSC yields a maximum PCE of 10.9% and good 500-h operational stability under continuous illumination. This is attributed to the unique thin-film structure, where the strong ionic bonding afforded by divalent 4AMP may provide near-full-coverage functionalization (encapsulation) of FASnI3 grain surfaces and grain boundaries, retarding O2/H2O ingression and mitigating Sn-defects for reduced photocarrier nonradiative recombination.