Abstract
In this paper, efficient phosphorescent white organic light-emitting diodes (WOLEDs) were fabricated based on ultrathin doping-free emissive layers and mixed bipolar interlayers. The energy transfer processes were proved via the research of WOLEDs with different interlayer thicknesses and transient photoluminescence lifetime. WOLEDs with optimized thickness of doping-free emissive layers show maximum current efficiency of 47.8 cd/A and 44.9 cd/A for three-colors and four-colors WOLEDs, respectively. The Commission Internationale de L’Eclairage coordinates shows a very slight variation of ( ± 0.02, ± 0.02) from 5793 cd/m2 to 11370 cd/m2 for three-colors WOLEDs and from 3038 cd/m2 to 13720 cd/m2 for four-colors WOLEDs, respectively. The stability of the spectra is attributed to the stable and sequential energy transfer among the various dyes. The color temperature of four-colors WOLEDs can be obtained from 2659 to 6636 by adjusting the thickness of ultrathin emissive layer.
Highlights
White organic light-emitting diodes (WOLEDs) have attracted much attention because of their advantages of low-cost, light weight, high-contrast, flexible and full-color[1,2,3,4]
The power efficiency of white organic light-emitting diodes (WOLEDs) based on the ultrathin doping-free emission layer (EML) is far from the requirement of practical lighting applications and lower than the traditional WOLEDs29,30, which is urgent to further improve
The high efficiency phosphorescent WOLEDs can be achieved by use of doping-free phosphorescent EMLs and mixed bipolar interlayers
Summary
White organic light-emitting diodes (WOLEDs) have attracted much attention because of their advantages of low-cost, light weight, high-contrast, flexible and full-color[1,2,3,4]. The traditional method to fabricate WOLEDs is co-evaporation the EMLs, which significantly improves electroluminescent (EL) efficiency[18]. It brings some problems in entire fabrication process. The co-evaporation technology increases the cost, which is an adverse factor of commercialization To solve these problems, there is a method to simplify the structures of devices by employing doping-free EMLs instead of the co-evaporation system. The power efficiency of WOLEDs based on the ultrathin doping-free EMLs is far from the requirement of practical lighting applications and lower than the traditional WOLEDs29,30, which is urgent to further improve. The high efficiency phosphorescent WOLEDs can be achieved by use of doping-free phosphorescent EMLs and mixed bipolar interlayers
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