Modification of PEDOT:PSS hole transporting layer to improve the efficiency and light stability of tin-lead perovskite solar cells

Mixed tin (Sn)-lead (Pb) halide perovskites are promising photovoltaic materials for efficient single- and multi-junction solar cells. However, the power conversion efficiency (PCE) and light stability of Sn-Pb perovskite solar cells (PSCs) are limited by the PEDOT:PSS hole transport layer (HTL). In this work, we introduce potassium citrate (PC) additives to modify PEDOT:PSS HTL. The performance of mixed Sn-Pb PSCs is boosted significantly after PC modification. Using this strategy, we demonstrated the best PCE of 22.67% with enhanced open circuit voltage (Voc) and fill factor (FF). The characterization for films and devices revealed that PC molecules significantly suppress non-radiative recombination and thus improve device performance. Owing to the reduced non-radiative recombination, the device with PC modification also exhibited improved light stability.