High Efficiency White Organic Light-Emitting Diodes from One Emissive Layer

Abstract

In this study, two-wavelength white organic light-emitting devices (WOLEDs) were fabricated using a single doped layer, which was obtained by forming a recombination zone in a single emissive layer. In this emissive layer, both blue emission and yellow emission were obtained using a 4,4'-bis(2,2'-diphenylethen-1-yl)biphenyl (DPVBi) host doped with a red fluorescent dye, 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB). The white light resulted from the excitation in this single emissive layer by controlling the concentration of fluorescent dye in the emissive layer. In addition, a higher efficiency could be obtained using organic layers/Li/Al in the WOLED structure instead of organic layers/LiF/Al. The electroluminescent (EL) spectrum of the device was not sensitive to the driving voltage of the device. The obtained WOLEDs showed a maximum luminance of approximately 64,200 cd/m2 and the device began to emit light (at luminance of 0.1 cd/m2) at 3.4 V. At a luminance of approximately 100 cd/m2, the external quantum and the power efficiencies were 2.47% and 4.27 lm/W, respectively.