Effect of Humidity on Crystal Growth of CuSCN for Perovskite Solar Cell Applications

Copper(I) thiocyanate (CuSCN) is one of the most robust hole‐transport materials for perovskite solar cells (PSCs). However, the power conversion efficiency of CuSCN‐based PSCs is low due to difficulty in crystallization of CuSCN. In this study, we focused on humidity conditions during the aging process of CuSCN‐based PSCs to improve their performance. PSCs aged in humid air, i. e., at a relative humidity of 70 %, exhibited better performance (efficiency; 10.6 %) than those aged in lower humidity (5.9 %) due to improved crystallinity of CuSCN layers. The results of the study provide insights into how to improve fabrication process of CuSCN‐based PSCs for higher stability and efficiency. Photovoltaic performance of CuSCN‐based perovskite solar cells was improved by aging in relative humidity at ∼70 %. Crystal growth of CuSCN was promoted and trap density at CuSCN/perovskite interface decreased.