A Si-Substituted Spirobifluorene Hole-Transporting Material for Perovskite Solar Cells
Yanqi Luo, Ramesh Kumar Chitumalla, So‐Yeon Ham, Deniz N. Cakan, Taewoo Kim, Sanghyun Paek, Ying Shirley Meng, Joonkyung Jang, David P. Fenning, Min‐cheol Kim
Abstract
Hybrid organic–inorganic perovskite solar cells (PSCs) have shown promise for next-generation photovoltaics. This study presents a simple approach for enhancing the performance and stability of PSCs by substituting the center carbon atom of the common hole transport material (HTM) Spiro-MeOTAD with a silicon atom. This modification, termed Si-Spiro, results in an increased hole mobility. A density functional theory simulation indicates that the enhanced hole mobility is due to the structural change of Si-Spiro. Electron beam-induced current microscopy measurements indicate improved charged extraction at the Si-Spiro/perovskite interface. A power conversion efficiency of 22.5% is achieved in Si-Spiro-based PSCs, outperforming standard Spiro-MeOTAD. Additionally, Si-Spiro-based PSCs demonstrate enhanced stability, maintaining over 90% of performance over 120 h of one-sun operation. Depth-profiling X-ray photoelectron spectroscopy revealed that Si-Spiro effectively blocks metal ion migration, which contributes to its enhanced stability. The findings suggest that Si-Spiro could be promising a HTM for high-performing, stable PSCs.