Defect passivation and phase regulation of quasi-2D perovskites for efficient blue light-emitting diodes

Abstract

Quasi-two-dimensional (quasi-2D) perovskites with the multiquantum well structures, large exciton binding energy and high photoluminescence quantum yields present promising candidates for constructing high-performance perovskite light-emitting diodes (PeLEDs). However, the performance of blue PeLEDs still remains inferior to that of green and red devices due to non-radiative recombination caused by vacancy defects and random phase distribution. Herein, an additive of disodium pytophosphate was introduced into the precursor solution of blue quasi-2D perovskites to passivate uncoordinated Pb²⁺ and regulate phase distribution. Defect passivation is achieved through the dynamic coordination of P=O groups to uncoordinated Pb²⁺ sites. Meanwhile, hydroxyl groups guide the assembly of the perovskite structure by forming hydrogen bonds with halides, which refines the crystallization process and mitigates low-dimensional phases. Consequently, the perovskite films with disodium pytophosphate exhibit the reduced defect density and homogenized phase distribution, significantly enhancing radiative recombination. The blue PeLEDs with an emission peak of 488 nm achieve a maximum luminance of 6464 cd/m 2 and a maximum external quantum efficiency of ~8.8%.