At present, the high defect density and strong nonradiative recombination rate of all-inorganic cesium lead bromide (CsPbBr3) perovskite light-emitting diodes (PeLEDs) seriously inhibit the improvement of their quantum efficiency. In this paper, the addition of a short-chain additive, diethylammonium bromide (DEABr), aims to control the generation of a quasi-2D large n-phase to optimize the surface morphology and construct two-dimensional/three-dimensional (2D/3D) heterojunction perovskite structures to enhance the EL efficiency of PeLEDs. Through Kelvin probe force microscopy (KPFM) characterization, we confirmed that the 2D phase grains with a low potential are locally formed on the surface of the perovskite film under the action of DEABr. The existence of the 2D phase effectively improved the surface morphology and suppressed surface defects. In addition, the in situ constructed 2D/3D heterojunction perovskite structure further increases the exciton radiative recombination rate and significantly improves the electroluminescent performance. By optimizing its doping concentration, the optimal all-inorganic PeLED displays a current efficiency (CE) of 30.3 cd A-1, an external quantum efficiency (EQE) of 9.6%, and a maximum brightness of 32,500 cd m-2. According to our results, the formation of 2D structures on the surface of the CsPbBr3 film can improve surface morphology issues and optoelectronic properties of the film.
Keywords: 2D/3D heterojunction; Kelvin probe force microscopy; in situ constructed; perovskite light-emitting diodes; surface morphology.