Control of the Color Coordinates of Blue Phosphorescent Organic Light-Emitting Diodes by Emission Zone

The mechanisms of charge balance and tuning of the color coordinates in blue phosphorescent organic light-emitting diodes were studied by controlling the emission- zone and electroluminescence (EL) spectrum. On the basis of the findings, this paper discusses different hole-injection and mobility factors such as the thickness of the hole injection layer (HIL), the HIL materials, the surface treatment, and the insertion of a buffer layer, which mainly enabled tuning of the color coordinates. The approximately 500-nmwavelength shoulder peak in the EL spectrum was influenced by the width and location of the emission zone, following the optical micro-cavity effect. Different emission zones were created by different types of hole injection and mobility, which simultaneously enhanced the device efficiency and tuning of the color coordinates. (C) 2013 The Electrochemical Society. All rights reserved.