Significant Lifetime Enhancement in QLEDs by Reducing Interfacial Charge Accumulation via Fluorine Incorporation in
Dong Seob Chung1, Tyler Davidson-Hall2, Giovanni Cotella3
1Department of Electrical and Computer Engineering, Waterloo Institute for Nanotechnology, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1, Canada. dschung@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.
