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Enhanced Hole Injection in Phosphorescent Organic Light-Emitting Diodes by Thermally Evaporating a Thin Indium Trichloride Layer

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journal contribution
posted on 24.10.2012, 00:00 by Chun-Hong Gao, Shi-Duan Cai, Wei Gu, Dong-Ying Zhou, Zhao-Kui Wang, Liang-Sheng Liao
An ultrathin layer of indium trichloride (InCl3) is thermally evaporated on the indium tin oxide (ITO) anode to enhance the hole injection in simplified phosphorescent organic light-emitting diodes (PHOLEDs). Comparing with the device with ultraviolet (UV)-ozone treatment, the device modified by InCl3 exhibits a maximum current efficiency of 82.2 cd/A measured at about 2000 cd/cm2 and 36% improvement in power efficiency measured at 20 mA/cm2. More importantly, more than three times improvement in half lifetime estimated at an initial luminance of 1000 cd/cm2 is achieved. The investigations using ultraviolet photoelectron spectroscopy, X-ray photoelectron spectroscopy, and the bias- and temperature-dependent current density–voltage characteristics in the related hole-dominated devices have revealed that the improved device performance is mainly attributed to the enhanced hole injection resulting from the lowered hole injection barrier height in the InCl3-modified devices.