Hindawi Publishing Corporation International Journal of Photoenergy Volume 2013, Article ID 831765, 7 pages http://dx.doi.org/10.1155/2013/831765 Research Article Highly Efficient White Organic Light-Emitting Diodes with Controllable Excitons Behavior by a Mixed Interlayer between Fluorescence Blue and Phosphorescence Yellow-Emitting Layers Chun-Hong Gao, Xiao-Bo Shi, Dong-Ying Zhou, Lei Zhang, Zhao-Kui Wang, and Liang-Sheng Liao Jiangsu Key Laboratory for Carbon-Based Functional Materials & Devices, Institute of Functional Nano & Sot Materials (FUNSOM), Soochow University, Suzhou, Jiangsu 215123, China Correspondence should be addressed to Zhao-Kui Wang; zhaokuiwang@hotmail.com and Liang-Sheng Liao; lsliao@suda.edu.cn Received 7 January 2013; Revised 18 March 2013; Accepted 19 March 2013 Academic Editor: K. N. Narayanan Unni Copyright © 2013 Chun-Hong Gao et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. A highly eicient hybrid white organic light-emitting diode (HWOLED) has been demonstrated with a mixed interlayer between luorescent blue and phosphorescent yellow-emitting layers. he device structure is simpliied by using a controllable luorescence- mixed interlayer-phosphorescence emission layer structure. he electroluminance (EL) performance can be modulated easily by adjusting the ratio of the hole-predominated material to the electron-predominated material in the interlayer. It is found that the HWOLED with a ratio of 3 : 2 exhibits a current eiciency of 34 cd/A and a power eiciency of 29 lm/W at 1000 cd/m 2 with warm white Commission Internationale de l’Eclairage (CIE1931) coordinates of (0.4273, 0.4439). he improved eiciency and adaptive CIE coordinates are attributed to the controllable mixed interlayer with enhanced charge carrier transport, optimized excitons distribution, and improved harvestings of singlet and triplet excitons. 1. Introduction Since irstly reported by Tang and Vanslyke in 1980s [1], organic light-emitting diodes (OLEDs) especially the white OLEDs (WOLEDs) [2] have drawn increasing attention for wide commercial applications in displays and solid-state lighting, owing to their thinness, lexibility, low operation voltage, wide-viewing angle, high resolution, and a fast response time. Several kinds of structures have been developed for the WOLED fabrications, such as single emitting layer (EML) [3–5], multi EML [6, 7], blue EML with down conversion layer [8], and tandem structures [9–12] employing luores- cent and/or phosphorescent emissive materials. Phospho- rescent materials are the outstanding candidates because of their potential for almost 100% internal quantum eiciency [13]. However, few blue phosphorescent materials could be considered as an appropriate candidate for WOLEDs until now owing to their short lifetime and high energy gap which causes diiculties in keeping color stability and in inding suitable host materials. Hybrid WOLEDs (HWOLEDs) with an architecture of luorescence blue- interlayer-phosphorescence complementary color (s)-inter- layer-luorescence blue (F-I-P-I-F), proposed by Sun et al. in 2006 [14], have been paid increasing attention due to the long-term stability of luorescence blue materials and the long lifetime of the color complementary phosphorescent dopants. he interlayer between luorescent blue-emitting layer (EML) and complementary phosphorescent EML plays an important role in the eiciency, brightness, and lifetime since it prevents the singlet energy transfer from the blue luores- cent emitter to the complementary phosphorescent emitters and minimizes the exchange energy losses. Various organic materials with hole-predominated property [15–17], electron- predominated property [18], ambipolar properties [19–22], and mixed interlayer (MI) with hole-predominated material and electron-predominated material [23–32] have been used as the interlayer. he MI is a simple way to efectively