A Universal and Versatile Hole Transport Layer “Activator” Enables Stable Perovskite Solar Cells with Efficiency Near 25%

Abstract Organic small molecules have been proven to be the most efficient and predominantly employed hole transport layers (HTLs) in perovskite solar cells (PSCs), the reliance of HTLs on additives like Li‐TFSI has been unavoidable, particularly in terms of the well‐known Spiro‐OMeTAD. However, Li‐TFSI aggregation in HTL results in the decreased performance and stability of PSCs with serious hysteresis. It is an urgent need to explore a universal strategy to solve Li‐TFSI‐induced issues. Herein, a pyrene‐based organic semiconductor (PC) as an effective and universal additive for HTL application is developed. It is found that the introduction of PC can efficiently improve the hot carriers extraction/transfer and reduce the charge recombination in the device. Consequently, PSCs based on Spiro‐OMeTAD+PC as a HTL exhibit an excellent PCE of 24.80% with a negligible hysteresis, much higher than the control device (22.14%). Additionally, the efficiency of the PC incorporated into another well‐known X60 HTL‐treated device is enhanced to 24.12% from the control device (22.04%), confirming its universal application in PSCs. Moreover, PC can effectively suppress the Li + aggregation in HTL, and the unencapsulated PSCs exhibit high stability. The findings in this work provide an effective and universal avenue to construct highly efficient and stable PSCs.