We increased the luminescent efficiency of perovskite light-emitting diodes (PeLEDs) by using a modified two-step deposition method combined with an interdiffusion process without additional solvent engineering or additive molecules. Methylammonium lead bromide (MAPbBr(3)) polycrystalline films with nanosized grains and low electronic disorder were fabricated by a modified two-step deposition process. The as-fabricated MAPbBr(3) films showed gradient concentration characteristics as a result of a gradient distribution of the MABr. Also, the MABr-gradient concentration structure was intensified by the interdiffusion process, showing improved performance of MAPbBr(3) PeLEDs with maximum current efficiency CEmax = 0.861 cd A(-1) and maximum luminance = 604 cd m(-2) with very narrow electroluminescence spectral width. This is the highest CEmax among MAPbBr(3)-based PeLEDs deposited by the two-step deposition method. (C) 2018 Author(s).