Acta Phys. -Chim. Sin. ›› 2010, Vol. 26 ›› Issue (10): 2752-2756.doi: 10.3866/PKU.WHXB20100949

• PHOTOCHEMISTRY AND SPECTROSCOPY • Previous Articles     Next Articles

Efficient Polymer White-Light-Emitting Devices Based on Two Complementary Phosphorescent Colors

LI Yan-Hu1, FANG Yuan2, ZOU Jian-Hua1, WANG Biao2, WU Hong-Bin1,3, PENG Jun-Biao1,3   

  1. 1. Institute of Polymer Optoelectronic Material and Devices, South China University of Technology, Guangzhou 510640,P. R. China;
    2. State Key Laboratory of Optoelectronic Materials and Technologies, Sun Yat-Sen University, Guangzhou 510275, P. R. China;
    3. Key Laboratory of Specially Functional Materials, Ministry of Education, South China University of Technology, Guangzhou 510640, P. R. China
  • Received:2010-05-10 Revised:2010-06-07 Published:2010-09-27
  • Contact: PENG Jun-Biao E-mail:psjbpeng@scut.edu.cn
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (U0634003, 60937001) and State Key Research Programof China (2009CB930604, 2009CB623604, 2008AA03A335, 20090325).

Abstract:

White polymer light -emitting diodes (WPLEDs) were fabricated by spin coating method using two complementary colors. The device structure used here is ITO/PEDOT (40 nm)/emitting layer (80 nm)/Ba (4 nm)/Al (120 nm). When the mass ratio of PVK:OXD -7:iridium bis(2 -(4,6 -difluorophenyl) -pyridinato -N,C2)picolinate (Firpic):tris(3 -(2,6 -dimethylphenoxy) -6-(thiophen -2-yl)pyridazine)iridium (Fs-1) was 63:27:10:0.25, white light with Commission Internationale deL 'Eclairage (CIE) coordinates of (0.30, 0.39) was obtained. The maximum current efficiency was 10.8 cd·A -1 and the maximum brightness was 4200 cd·m -2. To improve the hole -electron injection balance and the device 's character, a thin layer of water -soluble electronic transporting material was used to modify the cathode. In this case, efficient white light emission with a maximum current efficiency of 13.1 cd·A-1 anda maximum brightness of 6069 cd·m-2 was obtained. Using poly[(9,9 -bis(3 '-(N,N-dimethylamino) propyl) -2,7 -fuorene) -alt -2,7 -(9,9 -dioctylfuorene)] (PFN) (20 nm)/Al (120 nm) as the cathode resulted in CIE coordinates of (0.33, 0.39) and the EL spectrum was also found to be quite stable. The effects of charge trapping and energy transfer on device performance were discussed by considering the photoluminescence (PL) and electroluminescence (EL) spectra as well as the energy band diagramof the device.

Key words: Polymer light emitting diode, Two complementary white light, Energy transfer, Cathode modification

MSC2000: 

  • O644