Optimization of Composition with Reduced Phase Impurity in Quasi‐2D Perovskite for Electroluminescence

Abstract

Quasi‐2D‐layered perovskites have more exotic optical properties than their 3D halide perovskites congener, such as prominent excitonic features, higher photoluminescence (PL) yield, and composition‐induced energy transfer among different phases. However, there are known challenges in quasi‐2D perovskite where by default one gets a mixture of various phases (n = 1, 2, 3….3D) in one composition. Energy transfer processes occur among various phases, and optimization is needed to ensure one can get the best optical properties by targeting optimal phase purity. Herein, a detailed analysis of structural and optical properties of different perovskites (2D perovskite, quasi‐2D perovskite, and 3D perovskite) of (PEA)2(FAPbBr3)n−1PbBr4 series is done. The n = 3 composition with the least phase impurity is prepared, which provides a higher PL emission intensity than members of this series. Hence, the n = 3 composition (emissive layer) based perovskite light‐emitting diode (PeLED) is fabricated. Poly(9‐vinyl carbazole) (PVK) as an additional hole‐injection layer with poly(3,4‐ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) helps to suppress (1) the leakage current (effective blocking of electrons) and (2) the non‐radiative channels at the interface. Optimized thickness of emissive layer in PeLED (100 nm) gives a luminance efficiency of 15.4 cd A−1 and external quantum efficiency (EQE) of 4.32%.