1.Photonics Center, Nankai University, Tianjin 300071, China 2.Institute of Polymer Optoelectronic Material & Devices(IPOM), South China University of Technology, Guangzhou 510640, China
Abstract：In the present paper electroluminescence spectrum and Raman spectrum were used to study electro-degradation of polymer light emitting devices (PLEDs) of PFO-BT15, a new and high-efficiency emitting polymer synthesized by the institute of polymer optoelectronic material & devices(IPOM) in South China University of Technology.The PLEDs with a configuration of ITO glass/PEDOT(120 nm)/PFO-BT15(80 nm)/Ba(4 nm)/Al(200 nm) emitted green light at 550 nm when 5 V dc voltage was applied.Three of those devices were used to study the electro-degradation mechanism of PLEDs.Device A was deposited in vacuum box in dark room to keep sample fresh；Device B was first lighted with current of 1 mA·0.25 cm-2 for 200 minutes, then with current of 5 mA·0.25 cm-2 for 60 minutes, finally with current of 10 mA·0.25 cm-2 for 40 minutes；Device C was lighted with current of 20 mA·0.25 cm-2 until the electroluminescence failure.Our experimental results indicate that the degradation speeds highly depend on the current through the devices.The stressed devices show the decrease in electroluminescence efficiency.However, the luminescence spectrum of the stressed device did not change compared with the fresh device, which suggest that the structure of the luminescent polymer did not change with the electro-stress.Raman spectrum was employed to probe the structure changes of the materials used in the device.We found that the PEDOT Raman peak disappeared and the PFO-BT15 Raman peak still existed in electro-stress device.The results confirmed that it was the breakage of the PEDOT layer instead of degradation of emitting polymer, that led to the final failure of the PLEDs device.This work gives some valuable information for the design and development of highly stable organic light-emitting device.
[1] Cao Yong, Parker I D, Yu Gang.Advanced Display, 2001,(2)：3. [2] Do L M，Han E M，Niidome Y.J.Appl.Phys., 1994, 76(9)：5118. [3] Parker I D, Cao Y.J.Appl.Phys., 1999, 85(4)：2441. [4] Lim Shuang Fang, Ke Lin, Wang Wei.Appl.Phys.Lett., 2001, 78(15)：2116. [5] Me Elvain J, Antoniadis H, Hueschen M R.J.Appl.Phys., 1996, 80(10)：6002. [6] Lin Haibo, Xu Xiaoxuan, Yu Gang.Proceedings of SPIE, 2004, 5632：11. [7] LIN Hai-bo, XU Xiao-xuan, WU Hong-bin, et al(林海波，徐晓轩，吴宏滨，等).Chinese Journal of Luminescence(发光学报)，2005, 26(4)：469. [8] Adachi C, Nagai K, Tamoto N.Appl.Phys.Lett., 1995, 66：2679. [9] Han E M, Do L M, Niidome Y, et al.Chemistry Letters, 1994，(5)：969. [10] Fujihira M, Do L M, Koike A, et al.Appl.Phys.Lett., 1996, 68(13)：1787. [11] Burrows P, Bulovic F, Forrest S, et al.Appl.Phys.Lett., 1994, 65(23)：2922. [12] Slyke S V, Chen C, Tang C.Appl.Phys.Lett., 1996, 69(15)：2160. [13] TANG Ai-wei, TENG Feng, GAO Yin-hao, et al(唐爱伟, 滕 枫, 高银浩, 等).Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2006，26(12)：2169. [14] LIN Hai-bo, XU Xiao-xuan，WU Hong-bin, et al(林海波，徐晓轩，吴宏滨, 等).Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2004，24(6)：701. [15] YU Ge, XU Xiao-xuan, L Shu-hua, et al(于 舸, 徐晓轩, 吕淑华, 等).Spectroscopy and Spectral Analysis(光谱学与光谱分析)，2006，26(5)：869. [16] Kim Ji-seon, Ho Peter K H, Murphy Craig E, et al.Adv.Mater., 2002, 14：2006.
