All-inorganic and lead-free CsSnI₃ is emerging as one of the most promising candidates for near-infrared perovskite light-emitting diodes (NIR Pero-LEDs), which find practical applications including facial recognition, biomedical apparatus, night vision camera, and Light Fidelity. However, in the CsSnI₃-based Pero-LEDs, the holes injection is significantly higher than that of electrons, resulting in unbalanced charge injection, undesired exciton dissipation, and poor device performance. Herein, it is proposed to manage charge injection and recombination behavior by tuning the interface area of perovskite and charge-transporter. A dendritic CsSnI₃ structure is prepared on the hole-transporter, only making a bottom contact with the hole-transporter and exposing all other available crystal surfaces to the electron-transporter. In other words, the interface area of perovskite/electron-transporter is significantly higher than that of perovskite/hole-transporter. Moreover, the embedding interface of perovskite/electron-transporter can spatially confine holes and electrons, increasing the radiation recombination. By taking advantage of the dendritic structure, efficient lead-free NIR Pero-LEDs are achieved with a record external quantum efficiency (EQE) of 5.4%. More importantly, the dendritic structure shows great superiorities in flexible devices, for there is almost no morphology change after 2000-cycles of bends, and the fabricated Pero-LEDs can keep 93.4% of initial EQEs after 50-cycles of bends.

中文翻译：

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用于高效灵活的近红外钙钛矿发光二极管的树枝状 CsSnI3

全无机和无铅 CsSnI ₃正在成为近红外钙钛矿发光二极管 (NIR Pero-LED) 最有前途的候选者之一，其实际应用包括面部识别、生物医学设备、夜视相机和轻保真。然而，在基于 CsSnI ₃的 Pero-LED 中，空穴注入明显高于电子，导致电荷注入不平衡、激子耗散和器件性能不佳。在此，建议通过调整钙钛矿和电荷传输体的界面面积来管理电荷注入和复合行为。树枝状 CsSnI ₃在空穴传输器上制备结构，仅与空穴传输器底部接触，并将所有其他可用的晶体表面暴露给电子传输器。换句话说，钙钛矿/电子传输体的界面面积明显高于钙钛矿/空穴传输体的界面面积。此外，钙钛矿/电子传输体的嵌入界面可以在空间上限制空穴和电子，增加辐射复合。通过利用树枝状结构，实现了高效的无铅 NIR Pero-LED，外量子效率 (EQE) 达到了创纪录的 5.4%。更重要的是，树枝状结构在柔性器件中显示出极大的优势，弯曲 2000 次后几乎没有形态变化，制造的 Pero-LED 可以保持 93。