| CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY |
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Efficiency of Blue Organic Light-emitting Diodes Enhanced by Employing an Exciton Feedback Layer |
| Qian-Qian Yu, Xu Zhang, Jing-Xuan Bi, Guan-Ting Liu, Qi-Wen Zhang, Xiao-Ming Wu, Yu-Lin Hua, Shou-Gen Yin |
Key Laboratory of Display Materials and Photoelectric Devices of Ministry of Education, and Tianjin Key Laboratory of Photoelectric Materials and Devices, School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384
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Qian-Qian Yu, Xu Zhang, Jing-Xuan Bi et al 2016 Chin. Phys. Lett. 33 088503 |
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Abstract We report that a novel exciton feedback effect is observed by introducing the bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (BAlq) inserted between the emitting layer (EML) and the electron transporting layer in blue organic light emitting diodes. As an exciton feedback layer (EFL), the BAlq does not act as a traditional hole blocking effect. The design of this kind of device structure can greatly reduce excitons' quenching due to accumulated space charge at the exciton formation interface. Meanwhile, the non-radiative energy transfer from EFL to the EML can also be utilized to enhance the excitons' formation, which is confirmed by the test of photolumimescent transient lifetime decay and electroluminescence enhancement of these devices. Accordingly, the optimal device presents the improved performances with the maximum current efficiency of 4.2 cd/A and the luminance of 24600 cd/m$^{2}$, which are about 1.45 times and 1.75 times higher than those of device A (control device) without the EFL, respectively. Simultaneously, the device shows an excellent color stability with a tiny offset of the CIE coordinates ($\Delta x=\pm0.003$, $\Delta y=\pm0.004$) and a relatively lower efficiency roll-off of 26.2% under the driving voltage varying from 3 V to 10 V.
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Received: 10 March 2016
Published: 31 August 2016
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