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Photoluminescence characteristics of organic molecules in the accelerated aging organic light‐emitting diodes
Author(s) -
Lin Yang,
Guo Kunping,
Gao Zhixiang,
Wang Hua,
Li Chong,
Xu Tao,
Wei Bin
Publication year - 2013
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201330261
Subject(s) - oled , materials science , photoluminescence , optoelectronics , cathode , layer (electronics) , heterojunction , degradation (telecommunications) , delamination (geology) , composite material , chemistry , telecommunications , computer science , paleontology , biology , subduction , tectonics
We have employed the photoluminescent (PL) spectrum of an accelerated aging organic light‐emitting diode (OLED) to investigate the mechanisms of molecular decomposition in the whole and each organic functional layer using a bevel‐cutting and peel‐off method. The devices were operated at a constant current density of 37 mA/cm 2 and 70 °C until the luminance reached a half of the initial luminance. The results show a slight or even negligible degradation in PL intensity compared to unbiased devices, indicating that little cracked molecular structure and destroyed host–guest transfer mechanism occurred in organic materials of the biased device Scanning electron microscopy images of devices with bias demonstrated that the delamination at the interfaces of organic layers/Al and light‐emitting layer/hole transport layer occurs. We concluded that the charges accumulated at the interface of the heterojunction formed between adjacent organic layers with different energy barriers in or near the emissive layer, as well as the cathode/organic layer, should be mainly responsible for the degradation of OLEDs.