Zheng-Hong Lu

Department of Materials Science and Engineering, University of Toronto

Organic Light-Emitting Diodes for Solar Grade Lighting

In addition to retain high efficiency at high luminance, white OLEDs have to produce a color rendering index (CRI) suitable as general illumination sources. Over the last two decades, traditional inorganic semiconductor device physics has guided the OLED research community in device structure design and selection of materials. Various types of organic and inorganic materials have been progressively introduced in device fabrication. Many of these multilayered device structures have worked well, in particular for low luminance applications such as flat-panel displays. However, efficiency roll off (similar to efficiency droop in LED) at high luminance has become a major challenge for OLED lighting applications. In this talk I will review potential problems in these multilayered devices and its correlation with efficiency droop. In order to reduce this efficiency droop, considerations in design of device structure and in selection of materials will be discussed. This talk will also review the various device structures used in constructing WOLED, and will discuss the pros and cons of these device structures in addressing two equally important parameter, device efficiency and color rendering index (CRI). Device engineering methods using inter-zone and intra-zone exciton harvesting for improved efficiency and CRI will also be presented.