Localized Electron Density Engineering for Bright and Stable Near-Infrared Electroluminescence from All-Inorganic Lead-Free Tin Halides

Abstract

Near-infrared light-emitting diodes (NIR LEDs) with emission wavelengths over 900 nm offer promising applications, but creating efficient, bright, and stable NIR LEDs is still a major challenge. Here, we develop NIR LEDs that are efficient, bright, and stable, emitting beyond 900 nm based on all-inorganic CsSnI3 through the meticulous engineering of the localized electron density of Sn2+ using N,N′-methylenediacrylamide (MBAA). Experimental investigations and theoretical calculations reveal that the multiple lone electron pairs of C═O units in MBAA can form strong coordination bonds with Sn2+, resulting in a reduced defect density and intrinsic hole doping density, and improved stability of the CsSnI3. The resulting NIR LEDs peaking at 943 nm show a high radiance of 204 W sr–1 m–2, a high external quantum efficiency of 6.56%, and an exceptionally long operational half-lifetime of over 150 h at a high constant current density of 50 mA cm–2.