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Vol. 14 (2022)

Significant Lifetime Enhancement in QLEDs by Reducing Interfacial Charge Accumulation via Fluorine Incorporation in the ZnO Electron Transport Layer

https://doi.org/10.1007/s40820-022-00970-x
Dong Seob Chung
Department of Electrical and Computer Engineering, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
https://orcid.org/0000-0002-7376-7689
Tyler Davidson‑Hall
Department of Electrical and Computer Engineering, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
http://orcid.org/0000-0002-1319-9579
Giovanni Cotella
Ipswich Research Centre, Huawei Technologies Research & Development (UK) Ltd., Phoenix House (B55), Adastral Park, Ipswich IP5 3RE, UK
Quan Lyu
Ipswich Research Centre, Huawei Technologies Research & Development (UK) Ltd., Phoenix House (B55), Adastral Park, Ipswich IP5 3RE, UK
Peter Chun
Ottawa IC Laboratory, Huawei Canada, 19 Allstate Parkway, Markham, ON L3R 5B4, Canada
Hany Aziz
Department of Electrical and Computer Engineering, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON N2L 3G1, Canada
http://orcid.org/0000-0002-5973-4979

Corresponding Author: Hany Aziz

h2aziz@uwaterloo.ca

Nano-Micro Letters, Vol. 14 (2022), Article Number: 212

Abstract

ZnO nanoparticles are widely used for the electron transport layers (ETLs) of quantum dots light emitting devices (QLEDs). In this work we show that incorporating fluorine (F) into the ZnO ETL results in significant enhancement in device electroluminescence stability, leading to LT50 at 100 cd m−2 of 2,370,000 h in red QLED, 47X longer than the control devices. X-ray photo-electron spectroscopy, time-of-flight secondary ion mass spectroscopy, photoluminescence and electrical measurements show that the F passivates oxygen vacancies and reduces electron traps in ZnO. Transient photoluminescence versus bias measurements and capacitance–voltage-luminance measurements reveal that the CF4 plasma-treated ETLs lead to increased electron concentration in the QD and the QD/hole transport layer interface, subsequently decreasing hole accumulation, and hence the higher stability. The findings provide new insights into the critical roles that optimizing charge distribution across the layers play in influencing stability and present a novel and simple approach for extending QLED lifetimes.


Highlights:


1 Quantum dots light emitting devices (QLEDs) with extremely long half-lifetimes at 100 cd m−2, 2,370,000 h were successfully fabricated using CF4 plasma-treated ZnO nanoparticle electron transport layers.
2 A new experimental approach that probes changes in exciton lifetime under current flow was used to investigate the changes in carrier concentration in QLEDs.
3 Evidence of the dependence of QLED stability on electron and hole concentrations at the QD/HTL interface was revealed.

Keywords

Colloidal quantum dots Quantum dots light emitting device Device stability Zinc oxide nanoparticles Fluorine
Chung, Dong Seob, Tyler Davidson‑Hall, Giovanni Cotella, Quan Lyu, Peter Chun, and Hany Aziz. 2022. “Significant Lifetime Enhancement in QLEDs by Reducing Interfacial Charge Accumulation via Fluorine Incorporation in the ZnO Electron Transport Layer”. Nano-Micro Letters 14 (November):212. https://doi.org/10.1007/s40820-022-00970-x.
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