Improved out-coupling efficiency of organic light emitting diodes by manipulation of optical cavity length |
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| Affiliation: | 1. Department of Display Engineering, Pukyong National University, Busan 608-737, Republic of Korea;2. OLED Research Center, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700, Republic of Korea;3. Department of Materials Science and Engineering, Yonsei University, Seoul 120-749, Republic of Korea;4. Center for Nano-Photonics Convergence Technology, Korea Institute of Industrial Technology, Gwangju 500-480, Republic of Korea;1. Istituto di Nanotecnologia CNR-NANOTEC, Via Monteroni, 73100, Lecce, Italy;2. Dipartimento di Matematica e Fisica “Ennio De Giorgi”, Università Del Salento, Via per Arnesano, 73100, Lecce, Italy;3. State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and Engineering, Jilin University, Jilin, 130012, China;4. College of Science, Changchun University of Science and Technology, Changchun, 130012, China |
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| Abstract: | The relationship between thickness of electron transport layer (ETL) and device performance of organic light-emitting diodes (OLEDs) was investigated. Especially, we prepared various OLEDs by varying the thickness of ETL to investigate the difference of device performance. Very interestingly, the device efficiency of green phosphorescent organic light emitting diodes (PHOLEDs) was significantly improved when the thickness of ETL was optimized even though we did not change any materials for such devices except that we applied highly conductive Li doped ETL. This means that the only one factor which is associated with an improvement of device efficiency could be originated from the constructive optical interference. As a result, the simple modification of PHOLEDs only by changing the optical thickness condition causes a dramatic improvement of current efficiency (up to 82.4 cd/A) as well as external quantum efficiency (EQE, up to 23.8%), respectively. Those values correspond to the much more improved ones (by ∼34.4%) compared to those obtained from the normal devices with thin ETL as a reference. |
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| Keywords: | Green phosphorescent OLED Li doped ETL Efficiency Cavity effect Charge balance |
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