2D/3D Heterojunction perovskite light-emitting diodes with tunable ultrapure blue emissions

High performance blue light-emitting diodes are indispensable for solid-state lighting and full-color displays. Recently, tremendous efforts have been dedicated to boost the performance for blue perovskite light-emitting diodes (PeLEDs). In this work, we construct an ingenious 2D/3D heterostructure perovskite by long-chain organic halide salt post-treatment in blue perovskites for the first time. Organic halide salt post-treatment can form a 2D capping layer on the original 3D perovskite surface, thus to passivate defects and improve exciton radiative recombination rate. As a result, 2D/3D PeLEDs with tunable blue emissions (465, 475, and 486 nm), ultra-low turn-on voltages (3.0, 2.7, and 2.7 V), high brightness (928, 6727, and 9242 cd m−2), and excellent EQEs (2.11%, 6.29%, and 8.57%) are demonstrated. Moreover, due to the high phase homogeneity, the optimized PeLEDs exhibit ultrapure blue emissions (FWHM < 15 nm), in which the PeLED (465 nm) achieve ≈ 98% coverage of the Rec. 2020 standard.