Highly Stable Inverted CdSe/ZnS-Based Light-Emitting Diodes by Nonvacuum Technique ZTO as the Electron-Transport Layer

Sajid Hussain,Ahmad Raza,Wei Lei,Qasim Khan,Jing Chen,Fawad Saeed,Nasrud Din,Ali Asghar,Abida Parveen,Zhang Chao

doi:10.3390/electronics10182290

Sajid Hussain, Ahmad Raza + Show 8 more

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https://doi.org/10.3390/electronics10182290

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Journal: Electronics	Publication Date: Sep 17, 2021
Citations: 4	License type: CC BY 4.0

Affiliation: Southeast University, Shenzhen University

Abstract

CdSe/ZnS quantum dots (QDs) have attracted great consideration from investigators owing to their excellent photo-physical characteristics and application in quantum dot light-emitting diodes (QD-LEDs). The CdSe/ZnS-based inverted QD-LEDs structure uses high-quality semiconductors electron transport layers (ETLs), a multilayered hole transporting layers (HTLs). In QD-LED, designing a device structure with a minimum energy barrier between adjacent layers is very important to achieve high efficiency. A high mobility polymer of poly (9,9-dioctylfluorene-co-N-(4-(3-methylpropyl)) diphenylamine (TFB) was doped with 4,4′-bis-(carbazole-9-yl) biphenyl (CBP) with deep energy level to produce composite TFB:CBP holes to solve energy mismatch (HTL). In addition, we also improved the QD-LED device structure by using zinc tin oxide (ZTO) as ETL to improve device efficiency. The device turn-on voltage Vt (1 cd m−2) with ZTO ETL reduced from 2.4 V to 1.9 V significantly. Furthermore, invert structure devices exhibit luminance of 4296 cd m−2, current-efficiency (CE) of 7.36 cd A−1, and external-quantum efficiency (EQE) of 3.97%. For the QD-LED based on ZTO, the device efficiency is improved by 1.7 times.

Highlights

In recent years, Quantum dots (QDs) have attracted considerable attention as an active material because of their excellent optoelectrical properties, such as broadband absorption, bandgap turnability, narrow full-width half maximum (FWHM), high photoluminescence (PL), inherent photo-physical stability, and their advanced optoelectronic application in QD based light-emitting diodes (QD-LEDs) [1,2,3,4,5]
Coated glass has been used as a bottom substrate, zinc oxide nanoparticles (ZnO NPs) act as electron transport layer (ETL), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) acts as hole injection layer (HIL) [12,13], poly(9-vinlycarbazole) (PVK) [14]
Metal oxides such as zinc tin oxide (ZTO), titanium dioxide (TiO2 ), and zinc oxide nanoparticles (ZnO NPs) have been utilized as ETLs to enhance electron injection and charge balance in the QD EML [19,20]

Summary

Introduction

Quantum dots (QDs) have attracted considerable attention as an active material because of their excellent optoelectrical properties, such as broadband absorption, bandgap turnability, narrow full-width half maximum (FWHM), high photoluminescence (PL), inherent photo-physical stability, and their advanced optoelectronic application in QD based light-emitting diodes (QD-LEDs) [1,2,3,4,5]. Coated glass has been used as a bottom substrate, zinc oxide nanoparticles (ZnO NPs) act as electron transport layer (ETL), poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) acts as hole injection layer (HIL) [12,13], poly(9-vinlycarbazole) (PVK) [14]. Used for hole transporting layer (HTL), CdSe/ZnS QD acts as light-emissive layer (EML), and Au is deposited as top electrode [17,18]. Metal oxides such as zinc tin oxide (ZTO), titanium dioxide (TiO2 ), and zinc oxide nanoparticles (ZnO NPs) have been utilized as ETLs to enhance electron injection and charge balance in the QD EML [19,20]. There are still some difficulties with solution-processed metal oxide ETLs; through the solution processing of two consecutive layers, an intermix might develop, resulting in a leakage current inside the structure [21,22]

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