Superhalogen modulation: an effective approach for minimizing light-induced halide segregation in MAPb(IBr)

• Published in: Journal of materials chemistry. A, Materials for energy and sustainability Vol. 11; no. 35; pp. 194 - 1916
• Main Authors: Nandi, Pronoy, Park, Hyoungmin, Shin, Sooeun, Sharbirin, Anir S, Kim, Jeongyong, Kwon, Seok Joon, Park, Nam-Gyu, Shin, Hyunjung
• Format: Journal Article
• Published: 12.09.2023
• ISSN: 2050-7488; 2050-7496
• DOI: 10.1039/d3ta04201d

Significant reduction of light-induced halide segregation in organic-inorganic lead mixed-halide perovskites is essential for their implementation in tandem solar cells with existing silicon technology. Here, we address this challenge by a "One-stone-for-two-birds" strategy in which superhalogen anions of the molecular additive facilitate the reduction of halide defects and cations of the molecular additive play a role as a "controller" in the crystallization kinetics. We elucidate the mechanism by which BF 4 − substitution reduces light-induced phase segregation with different concentrations of BF 4 − at room temperature. From the bleach growth kinetics and segregation rate constant, we identify that 0.8% molar BF 4 − substitution in MAPbI 2.1 Br 0.9 results in minimum segregation, and thermodynamic arguments successfully explain the phenomena. Other experimental results, such as X-ray diffraction and photoluminescence under illumination, support our observation with assistance from stochastic simulation results for light-induced halide segregation dynamics. Consequently, the improved photovoltaic performance and enhanced photostability corroborate that suppressed halide segregation impacts device performance. We identify an efficient method to suppress halide segregation by adding BF 4 − as a modulator into MAPbI 2.1 Br 0.9 . Improved device performance indicate BF 4 − -incorporation is beneficial for the mitigation of defect trapping and halide ion hopping.