Critical role of additive-induced molecular interaction on the operational stability of perovskite light-emitting diodes

Chaoyang Kuang,Heyong Wang,Sai Bai,Kaichuan Wen,Sabina Abbrent,Jian Qing,Zhangjun Hu,Jianpu Wang,Chunyang Yin,Jiri Brus,Weidong Xu,Libor Kobera,Zhongcheng Yuan,Feng Gao

doi:10.1016/j.joule.2021.01.003

Abstract

Summary Despite rapid improvements in efficiency and brightness of perovskite light-emitting diodes (PeLEDs), the poor operational stability remains a critical challenge hindering their practical applications. Here, we demonstrate greatly improved operational stability of high-efficiency PeLEDs, enabled by incorporating dicarboxylic acids into the precursor for perovskite depositions. We reveal that the dicarboxylic acids efficiently eliminate reactive organic ingredients in perovskite emissive layers through an in situ amidation process, which is catalyzed by the alkaline zinc oxide substrate. The formed stable amides prohibit detrimental reactions between the perovskites and the charge injection layer underneath, stabilizing the perovskites and the interfacial contacts and ensuring the excellent operational stability of the resulting PeLEDs. Through rationally optimizing the amidation reaction in the perovskite emissive layers, we achieve efficient PeLEDs with a peak external quantum efficiency of 18.6% and a long half-life time of 682 h at 20 mA cm−2, presenting an important breakthrough in PeLEDs.

Highlights

The perovskite light-emitting diodes (LEDs) (PeLEDs) treated with EDEA molecules are fabricated following the optimal procedures developed in our previous work.[7]
For the PeLEDs treated with adipic acid (AAC) molecules, we systematically optimized the molar ratio of AAC and the film deposition conditions and achieved the optimal device performance with x = 0.5 (Figure S1)
Given that the thermal degradation of the perovskite emissive layer is arguably one of the critical factors deteriorating the device performance of PeLEDs,[26] we suggest that the superior thermal stability of the AAC-based perovskite films would be the main reason for the notably enhanced operational stability of the AAC-PeLEDs

Summary

Introduction

Low-cost, solution-processed metal halide perovskites possess widely tunable band gap, high photoluminescence (PL) efficiency, and excellent color purity, making them promising candidates for achieving cost-effective and high-performance light-emitting diodes (LEDs).[1,2,3,4,5] A range of useful optimization strategies on material compositions, thin-film depositions, and device architectures have rapidly improved external quantum efficiencies (EQEs) of perovskite LEDs (PeLEDs) to high values of over 20%.6–11 ensuring the long-term operational stability of stateof-the-art PeLEDs remains a critical challenge, hampering their practical applications and future commercialization.[3,4,12]Additives have been widely employed to boost the EQEs of PeLEDs during the past few years.[6,7,13,14,15,16,17,18,19,20,21,22,23,24] These additives, with rationally designed chemical structures and terminal moieties, help to reduce the defects in the perovskites or improve the thinfilm crystallinity, resulting in enhanced photoluminescence quantum yields (PL QYs) of the perovskite emissive layers.[6,7,13,14,16,20,23,25] Despite the effectiveness in enhancing the quantum efficiencies, it is largely unknown how these additives affect the operational stability of the devices.

Results

Conclusion