Enhanced Carrier Diffusion Enables Efficient Back-Contact Perovskite Photovoltaics

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 mu m. 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.

Automated summary

Back-contact architectures have the potential to enhance the 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. In this study, we demonstrate that perovskite films with a preferred out-of-plane orientation exhibit improved carrier dynamic properties. By adding guanidine thiocyanate, the films show significantly increased carrier lifetimes and mobilities, leading to enhanced carrier diffusion and improved charge collection. This approach enables the achievement of reproducible efficiencies of up to 11.2% in back-contact PSCs.