Mixed dimensional 0D/3D perovskite heterostructure for efficient green light-emitting diodes

Metal halide perovskites are emerging materials for next-generation optoelectronic devices, of which all-inorganic CsPbBr3 perovskite has attracted increasing attention due to outstanding stability and excellent photoelectric characteristics compared with organic-inorganic counterparts. However, the electroluminescence (EL) efficiencies of inorganic CsPbBr3 perovskite light emitting diodes (PeLEDs) were unsatisfactory because of high trap densities, leading to non-radiative recombination loss. Herein, by introducing potassium bromide (KBr), we successfully prepare zero-dimensional/three-dimensional (0D/3D) Cs4-xKxPbBr6/CsPbBr3 heterostructure perovskite films with suppressed trap density and improved photoluminescence quantum yield (PLQY). The deep energy level of 0D Cs4-xKxPbBr6 phase is confirmed using DFT calculation. Moreover, the formation of the unique heterostructure inhibits free charge diffusion at the grain boundary from suffering trapping recombination, which facilitates efficient radiative recombination in the 3D CsPbBr3 phase. Therefore, the optimised green PeLEDs shows a high external quantum efficiency (EQE) of 12.8 % which is around a six-fold improvement than the pristine one (2.1%) and a maximum brightness of 39400 cd m-2. Our work provides a rational charge carrier confinement strategy for developing high-performance PeLEDs and can be broadened to other potential perovskite materials, not restricted in the CsPbBr3-based perovskite films.