Multiple emissive layers white organic light emitting device with nanoplatforms patterning structure for improved current efficiency and color balance

摘要

In this paper, white organic light-emitting device (WOLED) with the structure of ITO/NPB/EML (blue)/CBP/EML (red)/CBP/EML (blue)/TPBi/LiF/Al was selected as reference. Then, the reference device was modified by nanoplatforms patterning structure at the TPBi/LiF or NPB/EML interface. The electroluminescence performance of above two kinds of devices was carefully investigated. The results indicate that WOLED with nanoplatforms at TPBi/LiF interface exhibits an enhanced current efficiency relative to reference device, and the enhancement factor is 1.52, which is due to improved light extraction efficiency. When nanoplatforms are located at the NPB/EML interface, WOLED shows more significantly improved current efficiency relative to reference device, and the enhancement factor is 1.80. Here, the improvement in current efficiency is attributed to increased light extraction efficiency and broadened carrier recombination zone. In addition, it is also found that WOLED with oanoplatforms located at the NPB/EML interface exhibits remarkably strengthened red light intensity in electroluminescence spectrum and good color balance, in which the intensity ratio of red-light to blue-light (I-red/I-blue) is 0.68, higher than that of reference WOLED (I-red/I-blue = 0.5). The implanting process of nanoplatforms patterning structure introduced in this paper is very simple and low-cost, which can be scaled up to large area WOLED manufacturing. (C) 2015 Elsevier B.V. All rights reserved.