The effects of sodium in ITO by pulsed laser deposition on organic light-emitting diodes

• Published in: Applied physics. A, Materials science & processing Vol. 101; no. 4; pp. 621 - 626
• Main Authors: Yong, Thian-Khok, Kee, Yeh-Yee, Tan, Sek-Sean, Yap, Seong-Shan, Siew, Wee-Ong, Tou, Teck-Yong
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.12.2010
• Subjects: Aluminum; Characterization and Evaluation of Materials; Condensed Matter Physics; Electric potential; Etching; Heating; Indium tin oxide; Machines; Manufacturing; Nanotechnology; Optical and Electronic Materials; Organic light emitting diodes; Physics; Physics and Astronomy; Processes; Secondary ion mass spectroscopy; Sodium; Surfaces and Interfaces; Thin Films; Pulse Laser Deposition; Pentacene; Aquaregia Solution; Brightness Performance
• ISSN: 0947-8396; 1432-0630
• DOI: 10.1007/s00339-010-5913-8

The depth profile of ITO on glass was measured by the time-of-flight secondary ion mass spectroscopy (TOFSIMS) which revealed high sodium (Na) ion concentration at the ITO surface as well as at the ITO–glass interface as a result of out diffusion with substrate heating. Effects of Na ions on the performance of organic light-emitting diode (OLED) were studied by etching away a few tens of nanometers off the ITO surface with a dilute aquaregia solution of HNO 3 :HCl:H 2 O. A single-layer, molecularly doped ITO/(PVK+TPD+Alq 3 )/Al OLEDs were fabricated on bare and etched ITO samples. Although the removal of a 10-nm layer of ITO surface increased the voltage range, brightness, and lifetime, it was insufficient to correlate these improvements with solely to the Na ion reduction without considering the surface roughness.