Efficient Perovskite Light-Emitting Diodes: Effect of Composition, Morphology, and Transport Layers.

Organic-inorganic metal halide perovskites are emerging as novel materials for light-emitting applications due to their high color purity, band gap tunability, straightforward synthesis, and inexpensive precursors. In this work, we improve the performance of three-dimensional perovskite light-emitting diodes (PeLEDs) by tuning the emissive layer composition and thickness and by using small-molecule transport layers. Additionally, we correlate PeLED efficiencies to the perovskite structure and morphology. The results show that the PeLEDs containing perovskites with an excess of methylammonium bromide (MABr) to lead bromide (PbBr2) in a 2:1 ratio and a layer thickness of 80 nm have the highest performance. The optimized device exhibits a peak luminance of 17 600 cd/m2 and an external quantum efficiency of 3.9%. Structural and morphological studies reveal a reduction in crystallite size and surface roughness with decreasing perovskite layer thickness and increasing ratio of MABr to PbBr2. Balanced charge injection, spatial charge confinement, and reduction in nonradiative sites can explain the enhanced performance by virtue of favorable morphology and transport layer choice.