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

Dong Seob Chung; Tyler Davidson-Hall; Giovanni Cotella; Quan Lyu; Peter Chun; Hany Aziz

doi:10.1007/s40820-022-00970-x

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

Nanomicro Lett. 2022 Nov 4;14(1):212. doi: 10.1007/s40820-022-00970-x.

Authors

Dong Seob Chung¹, Tyler Davidson-Hall², Giovanni Cotella³, Quan Lyu³, Peter Chun⁴, Hany Aziz⁵

Affiliations

¹ Department of Electrical and Computer Engineering, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada. dschung@uwaterloo.ca.
² Department of Electrical and Computer Engineering, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada.
³ Ipswich Research Centre, Huawei Technologies Research & Development (UK) Ltd., Phoenix House (B55), Adastral Park, Ipswich, IP5 3RE, UK.
⁴ Ottawa IC Laboratory, Huawei Canada, 19 Allstate Parkway, Markham, ON, L3R 5B4, Canada.
⁵ Department of Electrical and Computer Engineering, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada. h2aziz@uwaterloo.ca.

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.

Keywords: Colloidal quantum dots; Device stability; Fluorine; Quantum dots light emitting device; Zinc oxide nanoparticles.