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

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)(FAPbBr(3))(n-1)PbBr4 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%.