Transparent conductive electrode deposited by Cs-incorporated RF magnetron sputtering and evaluation of the damage in OLED organic layer

• Published in: Thin solid films 2008-07, Vol.516 (17), p.5907-5910
• Main Authors: Uchida, Takayuki, Kasahara, Yoshihiro, Otomo, Toshio, Seki, Shigeyuki, Wang, Meihan, Sawada, Yutaka
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Cross-disciplinary physics: materials science; rheology; Deposition by sputtering; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Electronics; Exact sciences and technology; Indium-tin-oxide; Low work function; Materials science; Methods of deposition of films and coatings; film growth and epitaxy; Optoelectronic devices; Organic light emitting device; Physics; Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; Surface double layers, schottky barriers, and work functions; Top emission
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2007.10.042

Top-emission organic light emitting devices (TE-OLEDs) and transparent OLEDs (TOLEDs) can be fabricated by employing a transparent cathode with a low work function instead of Mg:Ag or Al:Li films. However, most transparent conductive oxides (TCOs) have a high work function (WF). Therefore, we proposed a new sputtering method for fabricating a novel transparent conductive film. Generally, the sputtering process is a plasma process involving high-energy particles. It cannot avoid bombardment-induced damage to the organic layer. We fabricated ITO:Cs films and evaluated the damage to the organic layers. The turn-on threshold voltages of TOLEDs with such low WF (4.1 eV) ITO:Cs films decreased from 8.5 V to 3.5 V and higher efficiencies were obtained; however, large leak currents were observed.