Eco-friendly Sn-based perovskites show significant potential for highperformance 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 Sn 2+ to oxidize, resulting in detrimental Sn 4+ -induced defects and compromised device performance. Here, we present a targeted strategy to eliminate Sn 4+ -induced defects through moisture-triggered hydrolysis of tin tetrahalide, without degrading Sn 2+ in the CsSnI 3 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 nearinfrared 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.In recent years, there has been considerable interest in near-infrared perovskite light-emitting diodes (NIR Pero-LEDs) due to their remarkable advancements in efficiency development. [1][2][3][4] Nevertheless, the emission of these high-efficiency devices is currently restricted to the first NIR window (NIR-I, 700-900 nm). In contrast, the second NIR window (NIR-II, 900-1700 nm) emission offers applications in night vision, biological tissue analysis, biometric recognition, and communication due to its advantages, such as invisible emission, deeper tissue penetration, and reduced scattering. [5][6][7][8][9] Despite these promising prospects, the fabrication of potential commercial NIR-II Pero-LEDs remains challenging because of the limitation of the emission spectrum and toxicity in Pb-based perovskite components. 10 Recently, eco-friendly Sn-based Pero-LEDs emerged as a potential solution, featuring captivating NIR-II emission and showing significant progress in device efficiency. [11][12][13] However, despite achieving relatively high device efficiency, organic-inorganic hybrid components have not satisfied the crucial criteria of emitting spectra (emitting peak > 900 nm) and operational lifetime. 13,14 In contrast, the all-inorganic Sn-based perovskite CsSnI 3 features enhanced stability, robust emission properties, and more favorable NIR-II emitting spectra compared to their organic-inorganic hybrid counterparts. 12,15 Therefore, the all-inorganic CsSnI 3 -based Pero-LEDs exhibited a preferable operational lifetime of 23.6 h and a decent device efficiency of 5.4% in our early work. 16 However, due to the pronounced non-radiative recombination loss and ionic migration caused by Sn 4+ -induced defects, the operational lifetime and maximum external quantum efficiency (EQE max ) of NIR-II all-inorganic Sn-based Pero-LEDs are currently limited to 39.5 h 17 and 6.6% 18 , respectively. Previous reports have revealed the chemical instability of Sn 2+ , which is prone to losing its two active 5 s electrons and getting oxidized to Sn 4+ . 19 This process results in heavy self-doping
