Microstructural and electrical property changes of indium tin ozide anode induced by the variation of pulsed direct current frequency during face target sputtering and its influence on the J-V-L characteristic of organic light emitting diode
Investigations were carried out on the changes in the electrical and optical properties and surface roughness of the indium tin oxide (ITO) anode as a function of DC pulse frequency during facing-target sputtering. The current density-voltage-luminescence (J-V-L) characteristics of organic light emitting diodes (OLEDs) developed on the anodes were measured and analyzed in relation to the properties of ITO. When the pulsed DC frequency was less than 120 kHz, the resistivity of ITO was maintained well below 4.3× 10-4 Ω·cm and the optical energy band gap was greater than 4.1 eV, but these properties changed abruptly at 150 kHz with the morphological transition from columnar to equi-axed. Meanwhile, the surface roughness decreased continuously with increasing pulsed DC frequency up to 150 kHz. The J-V characteristics of the built-up OLED deteriorated slightly as the pulsed DC frequency increased to 120 KHz and then deteriorated rapidly at 150 kHz. The L-V curves, however, showed an improvement of luminescence as the frequency increased up to 120 kHz. These J-V-L characteristics imply that ITO which is more conductive and with a higher band gap can be obtained at the lower pulsed DC frequencies, which is desirable for higher current flow; however, better luminescence is closely related to smoother surfaces. Therefore, for the optimized J-V-L performance of OLEDs, a moderate pulse DC frequency, below the morphological transition of ITO, is desirable.
ITO OLED Pulsed DC frequency Facing target sputtering
Chul Yoon Sang Ho Kim
Dept.of Materials Engineering, Korea University of Technology and Education,1800 Chungjeol-ro, Byung Dept.of Materials Engineering, Korea University of Technology and Education, 1800 Chungjeol-ro, Byun
国际会议
The 11th Asian Symposium on Information Display(ASID09)(第11届亚洲信息显示会议)
广州
英文
146-151
2009-10-07（万方平台首次上网日期，不代表论文的发表时间）