The Improvement of Tin‐Based Perovskite Thin Film Quality to Enhance the Performance of Near‐Infrared PeLEDs Through Thiocyanate Modification

Abstract The morphological characteristics of in‐situ‐grown perovskite thin films are strongly influenced by the interface properties of previous layer. Additionally, their photoelectric characteristics are closely tied to the formed defects during the solution‐processing film for the oxidized tin ions, which significantly hinders the practicality of tin‐based perovskites in near‐infrared light‐emitting diodes (LEDs). Here, formamidine thiocyanate is employed to modify the interfacial behaviors of hole transport layer under the perovskite layer, resulting in reduced contact angle, improved surface wettability, enhancement of the crystallinity and film quality of tin‐based perovskite. Furthermore, by introducing guanidine thiocyanate into the precursor solution, the oxidation is successfully suppressed during the film formation of tin‐based perovskite, thereby reducing film defects to suppress non‐radiative recombination. A near‐infrared LEDs with a maximum external quantum efficiency reached 5.1%, representing a twofold improvement compared to unmodified devices. This advancement holds significant implications for the progression of tin‐based near‐infrared light emission technology.