Acta Phys. -Chim. Sin. ›› 2012, Vol. 28 ›› Issue (06): 1497-1501.doi: 10.3866/PKU.WHXB201203273

• PHOTOCHEMISTRY AND RADIATION CHEMISTRY • Previous Articles     Next Articles

Improving the Efficiency of Blue Organic Light-Emitting Diodes by Employing Cs-Derivatives as the n-Dopant

SHEN Li-Ying1, WU Xiao-Ming1, HUA Yu-Lin1, DONG Mu-Sen1, YIN Shou-Gen1, ZHENG Jia-Jin2   

  1. 1. Key Laboratory of Display Materials and Photoelectric Devices, Ministry of Education, Tianjin Key Laboratory of Photoelectric Materials and Devices, School of Materials Science and Engineering, Tianjin University of Technology, Tianjin 300384, P. R. China;
    2. College of Optoelectronics Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, P. R. China
  • Received:2011-12-28 Revised:2012-03-27 Published:2012-05-17
  • Contact: WU Xiao-Ming E-mail:wxm@mail.nankai.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (60906022, 60676051), Natural Science Foundation of Tianjin, China (10JCYBJC01100), Scientific Developing Foundation of Tianjin Education Commission, China (2011ZD02), and Jiangsu Natural Science Development Foundation for University, China (09KJB140006).

Abstract: The efficiency of organic light-emitting diodes (OLEDs) was markedly improved using the novel electron transporting material 2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (NBPhen) doped with Cs-derivatives including cesium carbonate (Cs2CO3) and cesium acetate (CH3COOCs) as the n-type dopant. The operating voltage of devices containing these materials as an n-type electron transporting layer (n-ETL) was significantly reduced. Optimized devices with Cs2CO3-doped or CH3COOCsdoped n-ETL (ITO/β-NPB/CBP:5%(w) N-BDAVBi/NBPhen/NBPhen:Cs2CO3 (or CH3COOCs)/Al) exhibited excellent electroluminescent performance with current densities of 551.80 and 527.88 mA·cm-2 at 14 V, corresponding brightnesses of 39750 and 39820 cd·m-2, and current efficiencies of 14.60 and 14.40 cd· A-1 at 10000 cd·m-2, respectively. These results were superior to that of conventional device (ITO/β-NPB/ CBP:5%(w)N-BDAVBi/NBPhen/Cs2CO3/Al) without an n-ETL, which exhibited a current density of 312.39 mA·cm-2 at 14 V, corresponding brightness of 25190 cd·m-2, and current efficiency of 9.45 cd·A-1 at 10000 cd·m-2. In addition, the reason for the increase in the efficiency of n-type doped devices has been analyzed based on the concept of the doping mechanism in organic semiconductors and the energy level scheme of the devices.

Key words: Organic light-emitting diodes, Cs2CO3, CH3COOCs, n-Type electron transporting layer, Electroluminescent performance

MSC2000: 

  • O644