Vapor‐Assisted In Situ Recrystallization for Efficient Tin‐Based Perovskite Light‐Emitting Diodes

Abstract Tin‐based perovskites are a promising candidates to replace their toxic lead‐based counterparts in optoelectronic applications, such as light‐emitting diodes (LEDs). However, the development of tin perovskite LEDs is slow due to the challenge of obtaining high‐quality tin perovskite films. Here, a vapor‐assisted spin‐coating method is developed to achieve high‐quality tin perovskites and high‐efficiency LEDs. It is revealed that solvent vapor can lead to in situ recrystallization of tin perovskites during the film‐formation process, thus significantly improving the crystalline quality with reduced defects. An antioxidant additive is further introduced to suppress the oxidation of Sn²⁺ and increase the photoluminescence quantum efficiency up to ≈30%, which is an approximately fourfold enhancement in comparison with that of the control method. As a result, efficient tin perovskite LEDs are achieved with a peak external quantum efficiency of 5.3%, which is among the highest efficiency of lead‐free perovskite LEDs.