Self-Assembled Monolayer-Decorated PEDOT:PSS for Balanced Hole Injection in Lead-Free Near-Infrared Perovskite Light-Emitting Diodes

Abstract Sn-based perovskite light-emitting diodes (PeLEDs) are promising lead-free alternatives for near-infrared optoelectronics, but suffer from severe interfacial losses and poor operational stability. Here, we report an effective hole-injection interface engineering strategy using a self-assembled monolayer (SAM) (MeO-2PACz) on PEDOT:PSS to realize high-performance CsSnI3-based PeLEDs. The SAM-modified interface optimizes energy-level alignment, suppresses interfacial nonradiative recombination, and improves perovskite film coverage and crystallinity, while reducing interfacial trap density and lattice microstrain. As a result, the optimized devices exhibit a maximum radiance of 196.5 W sr–1 m–2 and a peak external quantum efficiency (EQE) of 8.8% for 931 nm electroluminescence, representing state-of-the-art performance for CsSnI3-based near-infrared PeLEDs. This interfacial strategy is further demonstrated in red-emitting CsSnBr3 PeLEDs to achieve 2.31% EQE, highlighting its general applicability for energy-efficient, bright, and environmentally benign lead-free PeLEDs.