Phosphine oxide based semiconducting small molecule as an additive and an electron transport layer enables efficient and stable perovskite light-emitting devices

Abstract

Perovskite-based light-emitting diodes (Pe-LEDs) incorporate metal halide perovskites as the emissive layer in the form of polycrystalline thin films. Controlling the swift crystallization of these films poses challenges. However, the inclusion of phosphine oxide-derived additives during crystallization tempers this rapidity, yielding finer perovskite grains. This research studies how the type of phosphine oxide additive, be it insulating or semiconducting, modulates the optoelectronic characteristics of the methylammonium lead bromide (MAPbBr₃) perovskite layer, employing a nanocrystal pinning methodology. Comparing the semiconductor additive [2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine] (PO-T2T) with the insulating tri-octyl phosphine oxide (TOPO) revealed that the former ensures steadier photoluminescence across varying conditions. Optimized Pe-LED devices with PO-T2T outperform their counterparts in multiple aspects, including reproducibility, low turn-on voltage (2.2 V), brightness (20 300 cd m⁻²), efficiency (20.4 cd A⁻¹, 11.5 lm W⁻¹ and 4.4%), and notably, prolonged electroluminescence (EL) duration compared to standard or TOPO-based Pe-LED devices.