Effect of fabrication process on the microstructure and the efficiency of organic light-emitting diode

• Published in: Organic electronics Vol. 10; no. 3; pp. 459 - 464
• Main Authors: Lin, Wei-Chun, Lin, Yu-Chin, Wang, Wei-Ben, Yu, Bang-Ying, Iida, Shin-ichi, Tozu, Miyako, Hsu, Mao-Feng, Jou, Jwo-Huei, Shyue, Jing-Jong
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.05.2009; Elsevier
• Subjects: Applied sciences; C60 cluster ion beam; Electronics; Exact sciences and technology; Optoelectronic devices; Organic light-emitting diode; Secondary ion mass spectrometry (SIMS); Semiconductor electronics. Microelectronics. Optoelectronics. Solid state devices; X-ray photoelectron spectrometry (XPS); 85.60.Jb; Organic light-emitting diode; X-ray photoelectron spectrometry (XPS); C60 cluster ion beam; 81.70.Jb; 85.65.+h; Secondary ion mass spectrometry (SIMS); Performance evaluation; In situ; X ray spectrometry; Secondary ion mass spectrometry; Fabrication property relation; Manufacturing process; Spin-on coatings; Organic light emitting diodes; Optoelectronic device; Fullerenes; Microstructure; Vacuum deposition; Organic electronics; Concentration gradient; Charge carrier injection
• ISSN: 1566-1199; 1878-5530
• DOI: 10.1016/j.orgel.2009.01.013

Small molecular organic light-emitting diodes (OLEDs) can be fabricated by spin-coating and thermo-evaporation of organic materials. In this work, X-ray photoelectron spectrometry (XPS) and secondary ion mass spectrometry (SIMS) are used to examine the microstructure of emissive layers in organic LEDs prepared with different technique using in situ C 60 + sputtering. It is found that the Ir-containing guest molecule is enriched at the bottom-interface and a concentration gradient results from spin-coating while the opposite molecular distribution is observed with thermo-evaporation. Such a difference in microstructure affects the carrier-injection and carrier-transportation and is key to the dramatic difference (∼3.5×) in the efficiency of the resultant OLED devices.