Enhanced performance of organic light-emitting diodes by inserting wide-energy-gap interlayer between hole-transport layer and light-emitting layer |
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Authors: | Yusuke Honda Toshinori Matsushima Hideyuki Murata |
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Affiliation: | aSchool of Materials Science, Japan Advanced Institute of Science and Technology, 1–1 Asahidai, Nomi, Ishikawa 923-1292, Japan |
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Abstract: | We demonstrated that driving voltages, external quantum efficiencies, and power conversion efficiencies of organic light-emitting diodes (OLEDs) are improved by inserting a wide-energy-gap interlayer of (4,4′-N,N′-dicarbazole)biphenyl (CBP) between a hole-transport layer of N,N-di(naphthalen-1-yl)-N,N′-diphenyl-benzidine (α-NPD) and a light-emitting layer of tris(8-hydroxyquinoline)aluminum. By optimization of CBP thicknesses, the device with a 3-nm-thick CBP layer had the lowest driving voltage and the highest power conversion efficiency among the OLEDs. We attributed these improvements to enhancement of a carrier recombination efficiency and suppression of exciton–polaron annihilation. Moreover, we found that the degradation of the OLEDs is caused by decomposition of CBP molecules and excited-state α-NPD molecules. |
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Keywords: | Organic light-emitting diode Singlet-polaron annihilation Carrier recombination efficiency Degradation Unstable α -NPD excitons |
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