Performance Improvement of Organic Light Emitting Diodes Using Poly(N-vinylcarbazole) (PVK) as a Blocking Layer |
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Authors: | Lee Joo-Won kim jai-Kyeong Yoon Young-Soo |
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Affiliation: | 1. OLED Lighting Team, Convergence and Components & Materials Research Laboratory, New Devices & Materials Research Department, Electronics and Telecommunications Research Institute, 138 Gajeongro, yuseong‐gu, Daejeon, 305‐700, Korea;2. Opto‐electronic Materials Research Laboratory, Korea Institute of Science and Technology, Seoul, 136‐791, Korea |
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Abstract: | High efficiency organic light‐emitting‐devices (OLED) have been fabricated by incorporation of a polymeric layer as a controller of the unbalanced charge. In device configuration of ITO/PEDOT:PSS/PVK/Alq3/LiF:Al, poly(N‐vinylcarbazole) (PVK) was selected as a block‐ing layer (BL) because it has a hole transporting property and a higher band gap, especially a lower LUMO level than the emitting layer (Alq3) and a higher HOMO level than the hole injection layer (PEDOT: PSS). As a result, the optimal structure with this bl layer showed a peak efficiency of 6.89 cd/A and 2.30 lm/W compared to the device without the PVK layer of 1.08 cd/A, 0.27 lm/W. This result shows that the PVK layer could effec‐tively block the electrons from metal cathode and confine them in the emitting layer and accomplish the charge balance, which leads to enhanced hole‐electron balance for achieving high recombination efficiency. |
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Keywords: | organic light emitting diode blocking layer charge balance poly(N‐vinylcarbazole) (PVK) electron‐hole balance hybrid structure |
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