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

Abstract

Quasi-two-dimensional (quasi-2D) perovskites with multi-quantum well structures, large exciton binding energy and high photoluminescence quantum yields represent 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 pyrophosphate 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 PO 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 pyrophosphate exhibit reduced defect density and a homogenized phase distribution, significantly enhancing radiative recombination. The blue PeLEDs with an emission peak at 488 nm achieve a maximum luminance of 6464 cd m⁻² and a maximum external quantum efficiency of ∼8.8%.