Suppressing Disproportionation Decomposition in Sn-Based Perovskite Light-Emitting Diodes

Nontoxic Sn-based perovskite light-emitting diodes (Pero LEDs) have been developing rapidly in recent years. However, high-quality Sn-based perovskite films are hardly prepared because of the heavy self-doping of Sn4+ in the as-prepared films. Most previous reports indicate that the Sn4+ formation is mainly attributed to the Sn2+ oxidation by external oxidizers. Here, for the first time, we reveal that the disproportionation decomposition of Sn2+ during the annealing process plays a critical role in degrading device performance. To resolve this issue, we introduced formamidine thiocyanate into the perovskite precursor as a thermal-sacrificial agent to alleviate the disproportionation decomposition. Finally, we achieved efficient Pero-LEDs with a maximum external quantum efficiency of 5.3% and ultralow efficiency roll-off. This work provides a view of understanding the instability of Sn-based perovskite and presents a practical method to achieve efficient Sn-based Pero-LEDs by suppressing the disproportionation decomposition of Sn2+.