Edge stabilization in reduced-dimensional perovskites

Li Na Quan,Mengxia Liu,Dávid Ma ,Haifeng Yuan,Maarten B J Roeffaers,Yongbiao Zhao,Hairen Tan,Jiang Tang,Liang Gao,Jun Pan,Grant Walters,Abdul‐Hamid Emwas ,P Todorović ,James Fan ,Eva Bladt,Zachary Piontkowski,Randy P Sabatini ,Makhsud I Saidaminov,Osman M Bakr,Rafael Quintero-Bermúdez ,Sara Bals,Oleksandr Voznyy,F Pelayo Garcı́a De Arquer ,Yiying Li,Nini Wei,Dalaver H Anjum,Zheng‐Hong Lu ,David W Mccamant,Johan Hofkens,Edward H Sargent

doi:10.1038/s41467-019-13944-2

Abstract

Reduced-dimensional perovskites are attractive light-emitting materials due to their efficient luminescence, color purity, tunable bandgap, and structural diversity. A major limitation in perovskite light-emitting diodes is their limited operational stability. Here we demonstrate that rapid photodegradation arises from edge-initiated photooxidation, wherein oxidative attack is powered by photogenerated and electrically-injected carriers that diffuse to the nanoplatelet edges and produce superoxide. We report an edge-stabilization strategy wherein phosphine oxides passivate unsaturated lead sites during perovskite crystallization. With this approach, we synthesize reduced-dimensional perovskites that exhibit 97 ± 3% photoluminescence quantum yields and stabilities that exceed 300 h upon continuous illumination in an air ambient. We achieve green-emitting devices with a peak external quantum efficiency (EQE) of 14% at 1000 cd m−2; their maximum luminance is 4.5 × 104 cd m−2 (corresponding to an EQE of 5%); and, at 4000 cd m−2, they achieve an operational half-lifetime of 3.5 h.

Highlights

Reduced-dimensional perovskites are attractive light-emitting materials due to their efficient luminescence, color purity, tunable bandgap, and structural diversity
We focused on reduced-dimensional metal halide perovskites (MHPs) with a stoichiometry of PEA2Cs2.4MA0.6Pb4Br13
The optimization of the Cs-to-MA ratio revealed that an appropriate amount of MA was important to achieve high photoluminescence quantum yields (PLQYs) (Supplementary Table 1)[18]

Summary

Introduction

Reduced-dimensional perovskites are attractive light-emitting materials due to their efficient luminescence, color purity, tunable bandgap, and structural diversity. The edge states in reduced-dimensional MHPs refer to the states that are chemically unstable, structurally uncovered by organic amines These exciton-accepting edge states are susceptible to moisture and oxygen, and under photoexcitation they are the recipients of significant carrier transfer, especially in widebandgap materials[19]. We study the role of these sites in photodegradation and devise an edge-stabilization strategy to mitigate this problem This enables us to report the longest device operational lifetime at high luminance (4000 cd m−2), by a margin of >21 times, relative to the best prior report (at the initial luminance of 3800 cd m−2, with T50 = 10 min)[20]

Methods

Results

Conclusion