Improvement of Power Efficiency in Phosphorescent White Organic Light-Emitting Diodes Using p-Doped Hole Transport Layer

Abstract

We investigated the optical and electrical properties of molybdenum trioxide- (MoO<sub >3</sub>-) doped (1,1-bis[(di-4-tolylamino)phenyl]cyclohexane) (TAPC) films with different doping concentrations. Based on our results, we have fabricated white organic light emitting diodes (WOLEDs) with multi-emitting layer structures that consist of 1,3-bis(9-carbazolyl)benzene as a host and three phosphorescent dopants: iridium(III) bis[4,6-difluorophenyl]-pyridinato-N,<svg style="vertical-align:-1.95624pt;width:24.725px;" id="M1" height="18.7875" version="1.1" viewBox="0 0 24.725 18.7875" width="24.725" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(1.25,0,0,-1.25,0,18.7875)"> <g transform="translate(72,-56.97)"> <text transform="matrix(1,0,0,-1,-71.95,58.97)"> <tspan style="font-size: 12.50px; " x="0" y="0">C</tspan> </text> <text transform="matrix(1,0,0,-1,-63.61,64.14)"> <tspan style="font-size: 8.75px; " x="0" y="0">2</tspan> </text> <text transform="matrix(1,0,0,-1,-59.23,67.71)"> <tspan style="font-size: 6.25px; " x="0" y="0">′</tspan> </text> <text transform="matrix(1,0,0,-1,-56.43,58.97)"> <tspan style="font-size: 12.50px; " x="0" y="0">]</tspan> </text> </g> </g> </svg> picolinate as a blue dopant, bis(2-phenylbenxothiozolato-N,<svg style="vertical-align:-0.17554pt;width:19.525px;" id="M2" height="16.575001" version="1.1" viewBox="0 0 19.525 16.575001" width="19.525" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(1.25,0,0,-1.25,0,16.575)"> <g transform="translate(72,-58.74)"> <text transform="matrix(1,0,0,-1,-71.95,58.97)"> <tspan style="font-size: 12.50px; " x="0" y="0">C</tspan> </text> <text transform="matrix(1,0,0,-1,-63.61,64.14)"> <tspan style="font-size: 8.75px; " x="0" y="0">2</tspan> </text> <text transform="matrix(1,0,0,-1,-59.23,67.71)"> <tspan style="font-size: 6.25px; " x="0" y="0">′</tspan> </text> </g> </g> </svg>)iridium(III) (acetylacetonate) as an orange dopant, and bis(1-phenylisoquinoline) (acetylacetonate) iridium(III) as a red dopant. We improved the power efficiency and decreased driving voltage of WOLEDs by employing a MoO<sub >3</sub>-doped TAPC layer as a hole transport layer. 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Furthermore, the WOLED has a high color-rendering index, which is about 86 with the Commission Internationale de l&#x2019;Eclairage 1931 chromatic coordinates of (0.4303, 0.3893) and correlated color temperature of 3008&#x2009;K.