Efficient fluorescence/phosphorescence hybrid white organic light-emitting diodes (OLEDs) with single doped co-host structure have been fabricated. Device using 9-Naphthyl-10 -(4-triphenylamine)anthrancene as the fluorescent dopant and Ir(ppy)3 and Ir(2-phq)3 as the green and orange phosphorescent dopants show the luminous efficiency of 12.4% (17.6 lm/W, 27.5 cd/A) at 1000 cd/m2. Most important to note that the efficiency-brightness roll-off of the device was very mild. With the brightness rising up to 5000 and 10 000 cd/m2, the efficiency could be kept at 11.8% (14.0 lm/W, 26.5 cd/A) and 11.0% (11.8 lm/W, 25.0 cd/A). The Commission Internationale de L'Eclairage (CIE) coordinates and color rending index (CRI) were measured to be (0.45, 0.48) and 65, respectively, and remained the same in a large range of brightness (1000–10 000 cd/m2), which is scarce in the reported white OLEDs. The performance of the device at high luminance (5000 and 10 000 cd/m2) was among the best reported results including fluorescence/phosphorescence hybrid and all-phosphorescent white OLEDs. Moreover, the CRI of the white OLED can be improved to 83 by using a yellow-green emitter (Ir(ppy)2bop) in the device.
In this study, colloidal ternary ZnxCd1-xS white light quantum dots (WQDs) were prepared, which have the characteristics of broad emission window. We used epoxy, styrene ethylene butylene styrene block copolymer (SEBS), and silicone as encapsulate materials to pack the device. The results show that the Zn0.5 and Zn0.8 have band edge and surface state emission. The quantum yield (QY) and particle size of Zn0.5 and Zn0.8 WQDs is 19, 32 % and 4.5±0.5 and 3.1±0.5 nm, respectively. The white light-emitting diodes (WLEDs) were obtained by mixing WQDs with different resins, and pumping by UV chip. The luminous efficacy is 6.7 and 8.5 lm/W for Zn0.5 and Zn0.8-based WLED by using epoxy resin as encapsulate material. Moreover, the long period test can maintain 201 and 184 h for Zn0.5 and Zn0.8-based WLED, respectively. The results of this study present that the device encapsulated by epoxy resin can improve the luminous efficacy and stability of device. This outstanding finding may contribute to the future development of solid-state lighting (SSL).
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