Efficient nondoped blue organic light-emitting diodes based on phenanthroimidazole-substituted anthracene derivatives Shaoqing Zhuang a,c , Ronggang Shangguan a , Jiangjiang Jin a , Guoli Tu a , Lei Wang a,⇑ , Jiangshan Chen b,⇑ , Dongge Ma b , Xunjin Zhu c,⇑ a Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, People’s Republic of China b State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People’s Republic of China c Centre for Advanced Luminescence Materials, Department of Chemistry, Hong Kong Baptist University, Waterloo Road, Hong Kong, People’s Republic of China article info Article history: Received 31 May 2012 Received in revised form 12 July 2012 Accepted 20 August 2012 Available online 6 September 2012 Keywords: Blue material Anthracene Phenanthroimidazole Organic light-emitting devices abstract A series of new blue materials based on highly fluorescent di(aryl)anthracene and electron- transporting phenanthroimidazole functional cores: 2-(4-(anthracen-9-yl)phenyl)-1-phe- nyl-1H-phenanthro[9,10-d]imidazole (ACPI), 2-(4-(10-(naphthalen-1-yl)anthracen-9- yl)phenyl)-1-p-henyl-1H-phenanthro[9,10-d]imidazole (1-NaCPI), 2-(4-(10-(naphthalen- 2-yl)anthracen-9-yl)phenyl)-1-phenyl-1H-phenanthro[9,10-d]imidazole (2-NaCPI) were designed and synthesized. These materials exhibit good film-forming and thermal proper- ties as well as strong blue emission in the solid state. To explore the electroluminescence properties of these materials, three layer, two layer and single layer organic light-emitting devices were fabricated. With respect to the three layer device 4 using ACPI as the emitting layer, its maximum current efficiency reaches 4.36 cd A 1 with Commission Internationale del’Eclairage (CIE) coordinates of (0.156, 0.155). In the single layer device 10 based on ACPI, maximum current efficiency reaches 1.59 cd A 1 with Commission Internationale del’Eclai- rage (CIE) coordinates of (0.169, 0.177). Interestingly, both device 4 and 10 has low turn on voltage and negligible efficiency roll off at high current densities. Ó 2012 Elsevier B.V. All rights reserved. 1. Introduction Since the pioneering work by Tang and Van Slyke [1], significant progresses in materials and device engineering have led to the potential application of full-color OLEDs and solid-state lighting [2]. For full-color displays, it is essential to have the three primary colors, red, green and blue. Red and green phosphorescent electroluminescent devices with high efficiencies, long lifetimes, and proper CIE coordinates have been well developed. However, blue phosphorescent devices are still the bottleneck for the high CIE coordinates (y-coordinate value >0.30) and short de- vice lifetime [3]. Therefore, to achieve marketable OLEDs, the hunt for blue fluorescent materials and devices are still a subject of current interest [4]. Based on anthracene, an well-known building block and starting material in OLEDs, new diverse of blue material and corresponding devices have been reported previously [5]. For example, Park group [6] have synthesized carba- zole-based anthracene derivatives 3,6-di(anthracen-9-yl)- 9-phenyl-9H-carbazole (P-DAC) and attained device effi- ciency of 3.14 cd A 1 , color coordinates (0.16, 0.14), and threshold voltage 3.8 V. Li’s team [7] have shown fluorene based naphthylanthracene derivatives with a maximum luminance efficiency of 4.04 cd A 1 , CIE coordinates of (0.15, 0.13) and a turn on voltage of 4.1 V. Recently, phen- anthroimidazole derivatives have attracted great attention as electroluminescent materials because of their high thermal stability and efficient electron transporting ability. Huang’s group [8] reported bis(phenanthroimidazolyl)biphenyl 1566-1199/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.orgel.2012.08.032 ⇑ Corresponding authors. Tel./fax: +86 27 87793032 (L. Wang). E-mail addresses: wanglei@mail.hust.edu.cn (L. Wang), jschen@- ciac.jl.cn (J. Chen), xjzhu@hkbu.edu.cn (X. Zhu). Organic Electronics 13 (2012) 3050–3059 Contents lists available at SciVerse ScienceDirect Organic Electronics journal homepage: www.elsevier.com/locate/orgel