Highly efficient blue organic light-emitting diodes employing exciplex host

Abstract

The combination of relatively high efficiency and sky blue emission from co-host system phosphorescent organic light-emitting diodes (PhOLEDs) is essential for both display and lighting applications. Here, we provide a route to improve the efficiency of blue-emission organic molecules that forms exciplex in emission layer. The authors report efficient PhOLEDs using a highly transparent indium tin oxide (ITO) anode with high work function, which was prepared by DC sputtering under room temperature condition at chamber pressure of 2×10-3 Torr. The sputtered ITO anode shows a sheet resistance of 80 ω/sq, favorable injection work function of ∼ 5.20 eV, and high optical transmittance of ∼ 90% at the wavelength range of 400 to 500 nm in the visible light. In addition, electrical characterizations reveal the efficient transport property in di-[4-(N,N-ditolyl-Amino)-phenyl]cyclohexane (TAPC) and Tris(4-carbazoyl-9-ylphenyl)amine (TCTA) layers. The blue PhOLED based on exciplex forming host materials exhibits maximum external quantum efficiency of 28.5% along with a bottom emission brightness of 10,000 cd/m2, current efficiency of 58.6 cd/A , and power efficiency of 61.3 lm/W.