Targeted elimination of tetravalent-Sn-induced defects for enhanced efficiency and stability in lead-free NIR-II perovskite LEDs

Eco-friendly Sn-based perovskites show significant potential for high-performance second near-infrared window light-emitting diodes (900 nm – 1700 nm). Nevertheless, achieving efficient and stable Sn-based perovskite second near-infrared window light-emitting diodes remains challenging due to the propensity of Sn2+ to oxidize, resulting in detrimental Sn4+-induced defects and compromised device performance. Here, we present a targeted strategy to eliminate Sn4+-induced defects through moisture-triggered hydrolysis of tin tetrahalide, without degrading Sn2+ in the CsSnI3 film. During the moisture treatment, tin tetrahalide is selectively hydrolyzed to Sn(OH)4, which provides sustained protection. As a result, we successfully fabricate second near-infrared window light-emitting diodes emitting at 945 nm, achieving a performance breakthrough with an external quantum efficiency of 7.6% and an operational lifetime reaching 82.6 h. Guan et al. report a strategy of moisture-triggered selective hydrolysis of Sn4+ into Sn(OH)4, eliminating Sn4 + -induced defects in tin-based perovskites and enhancing the electron injection in NIR-II LED devices with peak emission of 945 nm and external quantum efficiency of 7.6%.