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Giant Enhancement of External Quantum Efficiency in Near‐UV Organic Light‐Emitting Diodes via Device Aging and Impedance Spectroscopy Analysis
Author(s) -
Li Dongliang,
Yuan Yongfang,
Xu Jiwen,
Wang Hua,
Liu Liming,
Yi Zichuan,
Wang Lihui,
Lu Zongliu,
Li Haiou,
Zhang Xiaowen
Publication year - 2021
Publication title -
physica status solidi (rrl) – rapid research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.786
H-Index - 68
eISSN - 1862-6270
pISSN - 1862-6254
DOI - 10.1002/pssr.202100041
Subject(s) - oled , materials science , electroluminescence , optoelectronics , dielectric spectroscopy , current density , quantum efficiency , diode , light emitting diode , layer (electronics) , chemistry , nanotechnology , electrode , physics , quantum mechanics , electrochemistry
The issue of device durability is scarcely reported for state‐of‐the‐art UV organic light‐emitting diodes (UV OLEDs), but it is of theoretical interest and plays a key role in commercial products. Herein, the effects of aging time on current density and radiance of near‐UV OLEDs are investigated. Devices are fabricated with 9‐(4′‐(4,5‐diphenyl‐4H‐1,2,4‐triazol‐3‐yl)‐(1,1′‐biphenyl)‐4‐yl)‐9H‐carbazole as the fluorescent molecule, poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonate) as the hole injection layer, and LiF as the electron injection layer. It is found that the current density decays much faster than radiance, and accordingly promotes the device external quantum efficiency from 2.5% initially to a giant value of 8.2% after a certain period of aging. Impedance spectroscopy is performed to study the carrier injection/transport capability by configuring a hole‐only cell (HOC) and an electron‐only cell (EOC). The transition curves of the impedance, phase, and capacitance as a function of voltage indicate that carrier injection/transport gradually decreases during aging, which accounts for the reduced current density and radiance. The electroluminescence spectra are independent of the decay process. The results provide a new approach for analyzing durability and advancing applications of UV OLEDs.