Customized Buried Interface for High Performance All‐Inorganic CsSnI 3 ‐Based NIR Perovskite Light‐Emitting Diodes via a Guanidinium Derivative
Xiuling Li, Xiang Guan, Shurui Chi, Junnan Wang, Bowen Feng, Jiaqi Wang, Jinli Liu, Chunli Zhao, Yourong Wu, Xueting Liu, Peng Wu, Renjing Chen, Zemin Wang, Zihao Zhu, Peng He, Xin Tong, Chenlu He, Kebin LinABSTRACT
CsSnI 3 ‐based perovskite light‐emitting diodes (PeLEDs) show great potential in near‐infrared (NIR) applications, yet device performance is limited by interfacial degradation at the acidic hole‐transport layer (HTL) based on Poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). Herein, a multifunctional guanidine derivative of N‐(3‐methoxy‐phenyl)‐guanidine (NMPG), is used to modify the buried interface between the CsSnI 3 perovskite and the HTL. NMPG deprotonates the polystyrene sulfonic acid (PSSH) of PSS and reduces the acidity of PEDOT:PSS, while its methoxy and C═N groups coordinate with Sn 2+ , effectively inhibiting Sn 2+ oxidation, passivating Sn (II) induced defects. This customized buried interface enables uniform and discrete growth of perovskite grain, improves charge injection balance, and enhances vertical compositional and optical homogeneity. As a result, the target PeLEDs achieve a competitive maximum external quantum efficiency (EQE) of 9.0% and a high average EQE of 8.4%, significantly outperforming the control device ( EQE max = 6.6%, EQE ave = 5.5%). The target PeLEDs also demonstrate superior operational stability, with a T 50 lifetime of 67.9 h, representing a 5‐fold improvement compared to the control PeLEDs. This work reveals the pivotal role of buried interface chemistry and presents a viable molecular design strategy for achieving high‐performance CsSnI 3 ‐based PeLEDs.