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Journal of the Optical Society of Korea

Journal of the Optical Society of Korea


  • Vol. 13, Iss. 1 — Mar. 25, 2009
  • pp: 65–74

Parametric Studies of Pulsed Laser Deposition of Indium Tin Oxide and Ultra-thin Diamond-like Carbon for Organic Light-emitting Devices

Teck-Yong Tou, Thian-Khok Yong, Seong-Shan Yap, Ren-Bin Yang, Wee-Ong Siew, and Ho-Kwang Yow  »View Author Affiliations

Journal of the Optical Society of Korea, Vol. 13, Issue 1, pp. 65-74 (2009)

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Device quality indium tin oxide (ITO) films are deposited on glass substrates and ultra-thin diamond-like carbon films are deposited as a buffer layer on ITO by a pulsed Nd:YAG laser at 355 nm and 532 nm wavelength. ITO films deposited at room temperature are largely amorphous although their optical transmittances in the visible range are > 90%. The resistivity of their amorphous ITO films is too high to enable an efficient organic light-emitting device (OLED), in contrast to that deposited by a KrF laser. Substrate heating at <TEX>$200^{\circ}C$</TEX> with laser wavelength of 355 nm, the ITO film resistivity decreases by almost an order of magnitude to <TEX>$2{\times}10^{-4}\;{\Omega}\;cm$</TEX> while its optical transmittance is maintained at > 90%. The thermally induced crystallization of ITO has a preferred <111> directional orientation texture which largely accounts for the lowering of film resistivity. The background gas and deposition distance, that between the ITO target and the glass substrate, influence the thin-film microstructures. The optical and electrical properties are compared to published results using other nanosecond lasers and other fluence, as well as the use of ultra fast lasers. Molecularly doped, single-layer OLEDs of ITO/(PVK+TPD+<TEX>$Alq_3$</TEX>)/Al which are fabricated using pulsed-laser deposited ITO samples are compared to those fabricated using the commercial ITO. Effects such as surface texture and roughness of ITO and the insertion of DLC as a buffer layer into ITO/DLC/(PVK+TPD+<TEX>$Alq_3$</TEX>)/Al devices are investigated. The effects of DLC-on-ITO on OLED improvement such as better turn-on voltage and brightness are explained by a possible reduction of energy barrier to the hole injection from ITO into the light-emitting layer.

© 2009 Optical Society of Korea

OCIS Codes
(250.3680) Optoelectronics : Light-emitting polymers
(310.1860) Thin films : Deposition and fabrication
(310.7005) Thin films : Transparent conductive coatings

Original Manuscript: December 16, 2008
Revised Manuscript: April 2, 2009
Manuscript Accepted: February 6, 2009
Published: March 25, 2009

Teck-Yong Tou, Thian-Khok Yong, Seong-Shan Yap, Ren-Bin Yang, Wee-Ong Siew, and Ho-Kwang Yow, "Parametric Studies of Pulsed Laser Deposition of Indium Tin Oxide and Ultra-thin Diamond-like Carbon for Organic Light-emitting Devices," J. Opt. Soc. Korea 13, 65-74 (2009)

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