Enhanced Carrier Diffusion Enables Efficient Back‐Contact Perovskite Photovoltaics
Boya Zhao, Lara V. Gillan, Andrew D. Scully, Anthony S. R. Chesman, Boer Tan, Xiongfeng Lin, Jingying Liu, Kevin J. Rietwyk, Siqi Deng, Christopher G. Bailey, Yi‐Bing Cheng, Dane R. McCamey, Udo Bach
Abstract
Back-contact architectures offer a promising route to improve the record efficiencies of perovskite solar cells (PSCs) by eliminating parasitic light absorption. However, the performance of back-contact PSCs is limited by inadequate carrier diffusion in perovskite. Here, we report that perovskite films with a preferred out-of-plane orientation show improved carrier dynamic properties. With the addition of guanidine thiocyanate, the films exhibit carrier lifetimes and mobilities increased by 3-5 times, leading to diffusion lengths exceeding 7 μm. The enhanced carrier diffusion results from substantial suppression of nonradiative recombination and improves charge collection. Devices using such films achieve reproducible efficiencies reaching 11.2 %, among the best performances for back-contact PSCs. Our findings demonstrate the impact of carrier dynamics on back-contact PSCs and provide the basis for a new route to high-performance back-contact perovskite optoelectronic devices at low cost.