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Stable efficiency roll-off in phosphorescent organic light-emitting diodes

2008; American Institute of Physics; Volume: 92; Issue: 2 Linguagem: Inglês

10.1063/1.2836270

1520-8842

Sung Hyun Kim, Jyongsik Jang, Kyoung Soo Yook, Jun Yeob Lee,

Luminescence and Fluorescent Materials

Origin of efficiency roll-off in phosphorescent organic light-emitting diodes was investigated with triplet mixed host devices and stable devices with little efficiency roll-off was developed. Efficiency roll-off was significant in the device with narrow recombination zone (RZ) and charge leakage out of emitting layer at high luminance was critical to efficiency roll-off. Efficiency roll-off could be reduced in triplet mixed host device with broad RZ and little charge leakage at high driving voltage. Triplet mixed host devices with an exciton blocking layer showed a quantum efficiency over 90% of maximum quantum efficiency at a luminance of 20000cd∕m2.