Core/Shell ZnO/ZnS Nanoparticle Electron Transport Layers Enable Efficient All‐Solution‐Processed Perovskite Light‐Emitting Diodes

Abstract

Solution‐processed perovskite‐based light‐emitting diodes (PeLEDs) are promising candidates for low‐cost, large‐area displays, while severe deterioration of the perovskite light‐emitting layer occurs during deposition of electron transport layers from solution in an issue. Herein, core/shell ZnO/ZnS nanoparticles as a solution‐processed electron transport layer in PeLED based on quasi‐2D PEA2Csn−1PbnBr3n+1 (PEA = phenylethylammonium) perovskite are employed. The deposition of ZnS shell mitigates trap states on ZnO core by anchoring sulfur to oxygen vacancies, and at the same time removes residual hydroxyl groups, which helps to suppress the interfacial trap‐assisted non‐radiative recombination and the deprotonation reaction between the perovskite layer and ZnO. The core/shell ZnO/ZnS nanoparticles show comparably high electron mobility to pristine ZnO nanoparticles, combined with the reduced energy barrier between the electron transport layer and the perovskite layer, improving the charge injection balance in PeLEDs. As a result, the optimized PeLEDs employing core/shell ZnO/ZnS nanoparticles as a solution‐processed electron transport layer exhibit high peak luminance reaching 32 400 cd m−2, external quantum efficiency of 10.3%, and 20‐fold extended longevity as compared to the devices utilizing ZnO nanoparticles, which represents one of the highest overall performances for solution‐processed PeLEDs.

Low-dimensional nanomaterial-enabled efficient and stable perovskite light-emitting diodes: recent progress and challenges

“…5a). 80 The ZnS shell can effectively suppress trap emission and interface non-radiation recombination of the ZnO core, at the same time, more favorable band alignment significantly improves the injection capability of electrons from the ETL to the perovskite layer (Fig. 5b and c).…”

Advancements in Interfacial Engineering for Perovskite Light‐Emitting Diodes

“…This indicates a significant improvement in device performance by reducing interface defects. [37] Extensive research has illuminated the significant influence of electron density and nucleophilicity, which can serve as a passivating mechanism for surface defects. [38] Wang et al reported on the molecular design of an ETL material with a more nucleophilic core group to enhance its electron-donating capability ultimately leading to the passivation of surface defects in the perovskite emissive layer at the interfacial region.…”

“…Additionally, the adsorption energy becomes more Reproduced with permission. [37] © 2023 WILEY-VCH GmbH negative, indicating enhanced interfacial electron transfer between the perovskite layer and the ETL through the incorporation of this highly nucleophilic material. Since these vacancy defects contribute significantly to trap-assisted nonradiative recombination and carrier accumulation, the theoretically designed passivation-capable ETL material demonstrated enhanced perovskite crystal quality by reducing Pb 2 + vacancies and surface defects.…”

Engineering Colloidal Perovskite Nanocrystals and Devices for Efficient and Large-Area Light-Emitting Diodes

“…In inverted structure PNC-LEDs, PEI interlayer reduces the workfunction of underlying ZnO layer, and ZnCl 2 interlayer in the middle of PNC layers slows down the transport of charge carriers, both of which were used to increase the electron injection and improve charge balance in devices. Furthermore, all-inorganic electron transport layer such as ZnO/ZnS core/shell nanocrystals were used to increase the electron injection and improve charge balance in devices …”