Boosting CsSnI₃-based near-infrared perovskite light-emitting diodes performance via solvent coordination engineering

Due to their unique photoelectric properties, nontoxic tin-based perovskites are emerging candidates for efficient near-infrared LEDs. However, the facile oxidation of Sn2+ and the rapid crystallization rate of tin-based perovskites result in suboptimal film quality, leading to inferior efficiencies of tin-based perovskite light-emitting diodes (Pero-LEDs). In this study, we investigate the influence of commonly used solvents on the quality of the CsSnI3 films. Remarkably, DMSO exhibits a stronger interaction with SnI2, forming a stable intermediate phase of SnI2 center dot 3DMSO. This intermediate effectively inhibits the oxidation of Sn2+ and slows down the crystallization rate, bringing in lower defect state density and higher photoluminescence quantum yield of the prepared perovskite films. Consequently, the corresponding Pero-LEDs achieve a maximum external quantum efficiency (EQE) of 5.6%, among the most efficient near-infrared Pero-LEDs. In addition, the device processes ultra-low efficiency roll-off and high reproducibility. Our research underscores the crucial role of solvent-perovskite coordination in determining film quality. These findings offer valuable guidance for screening solvents to prepare highly efficient and stable tin-based perovskites.