Simplified phosphorescent organic light-emitting diodes with a WO3-doped wide bandgap organic charge transport layer |
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| Affiliation: | 1. Department of Chemistry, CICECO, University of Aveiro, Campus Universitário de Santiago, 3810-193 Aveiro, Portugal;2. Laboratory of Separation and Reaction Engineering, Associate Laboratory LSRE/LCM, Department of Chemical Engineering, Faculty of Engineering, University of Porto, Rua Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal;1. University of Limerick, V94T9PX, Limerick, Ireland;2. University of Genoa, 16145, Genova, Italy |
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| Abstract: | The effects of p-type doping of wide bandgap ambipolar 4,4′-N,N′-dicarbazolebiphenyl (CBP) with WO3 were investigated through detailed electrical device characterization. It was found that, to achieve effective doping for improved hole injection and transport, the doping level should be greater than 20 mol% and the doped layer should be at least 10 nm thick. A large downward shift of the Fermi level in WO3-doped CBP causes band bending and depletion at the doped/undoped CBP interface, resulting in an additional energy barrier which hampers hole transport. Simplified green phosphorescent organic light-emitting diodes (PhOLEDs) with CBP as the hole transport and host material were fabricated. With a WO3-doped hole transport layer, the PhOLEDs attained brightness of 11,163 cd/m2 at 20 mA/cm2, and exhibited an improved reliability under constant-current stressing as compared to undoped PhOLEDs. |
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| Keywords: | Electrical doping Electroluminescence Metal oxide Organic light-emitting diode |
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