Different Passivation Strategies in Metal-Halide Perovskite Light-Emitting Diodes

Abstract

Halide perovskite has emerged as one of the most attractive classes of materials for future optoelectronic devices due to its highly tunable band gap‚ high photoluminescence quantum yield (PLQY)‚ high charge-carrier mobility‚ and long carrier diffusion length․ PeLEDs based on lead halide perovskites have been reported with external quantum efficiency (EQE) exceeding 30% and device lifetimes reaching as high as 180000 hours for green and red emissions․ The high darkness‚ poor stability‚ and performance of pure-blue PeLEDs (460 to 470 nm) remain a challenge due to the deep trap states‚ halide ion migration‚ and unregulated crystallizing phase․ These factors lead to non-radiative recombination losses and device instability․ Therefore‚ in this review‚ we focus on the novel molecular passivation strategies involving fluorinated phosphonic acid‚ phosphorus oxychloride‚ choline chloride‚ malonamide‚ and tridecylamine in different perovskite systems․ Despite their difference in chemical composition‚ these passivators have improved device performance by passivating undercoordinated Pb²⁺ ions and/or through the stabilization of the halide framework via ionic/hydrogen bonding‚ with concomitant improvements in PLQY‚ EQE‚ and operational stability․ Nevertheless‚ pure blue PeLEDs still lag behind their green and red counterparts‚ indicating the need for optimized ligand engineering‚ defect passivation‚ and device architecture․