Peptide-Engineered Interface to Improve the Efficiency of Pure Red Tin Halide Perovskite LEDs by Controlling Crystallization and Reducing Oxidation

Tin (Sn)-based perovskite light-emitting diodes (PeLEDs) have garnered significant attention owing to their superior optoelectronic properties, affordable solution processing, and environmental friendliness. However, the properties of Sn-PeLEDs trail those of their lead (Pb) counterparts. The main obstacle is the easy oxidation of Sn²⁺ to Sn⁴⁺ as well as fast crystallization, leading to poor film quality with many defects. Herein, a convenient and effective interface engineering strategy is reported to fabricate (2-thiopheneethylamine)₂SnI₄ (TEA₂SnI₄) PeLEDs by introducing different peptides into the PEDOT:PSS hole-transport layer (HTL). Benefiting from the interaction between the peptide molecules and the Sn-perovskite nuclei, the crystallization dynamics are effectively adjusted, leading to an improved film morphology. At the same time, the multiple functional groups of peptides can suppress Sn²⁺ oxidation and passivate interface defects. Therefore, perovskite films with improved luminescence efficiency are obtained. The perovskite films are further used for the fabrication of pure red PeLEDs with enhanced performance. In particular, the optimized devices based on Leu-Gly-Gly (LGG) achieve a peak external quantum efficiency of 0.5% and a brightness of 136 cd m^–2, which are about 2 and 3 times larger, respectively, than those of the reference device. This research offers a general strategy to improve the performance of Sn-PeLEDs via peptide interface engineering.