title: Influence of vacuum chamber impurities on the lifetime of organic light-emitting diodes.
abstract: We evaluated the influence of impurities in the vacuum chamber used for the fabrication of organic light-emitting diodes on the lifetime of the fabricated devices and found a correlation between lifetime and the device fabrication time. The contact angle of the ITO substrates stored the chamber under vacuum were used to evaluate chamber cleanliness. Liquid chromatography-mass spectrometry was performed on Si wafers stored in the vacuum chamber before device fabrication to examine the impurities in the chamber. Surprisingly, despite the chamber and evaporation sources being at room temperature, a variety of materials were detected, including previously deposited materials and plasticizers from the vacuum chamber components. We show that the impurities, and not differences in water content, in the chamber were the source of lifetime variations even when the duration of exposure to impurities only varied before and after deposition of the emitter layer. These results suggest that the impurities floating in the vacuum chamber significantly impact lifetime values and reproducibility.
authors.affiliation: Fukuoka i3-Center for Organic Photonics and Electronics Research (i3-OPERA), 5-14 Kyudai-shinmachi, Nishi, Fukuoka 819-0388, Japan.|Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Fujimoto
authors.affiliation: Technology Innovation Center, Sumika Chemical Analysis Service, Ltd. (SCAS), 7-5, Kikumoto-cho 1-chome, Niihama, Ehime, 792-0801, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Suekane
authors.affiliation: Technology Innovation Center, Sumika Chemical Analysis Service, Ltd. (SCAS), 1-135, Kasugade-Naka 3-chome, Konohana-ku, Osaka, 554-0022, Japan.
authors.forename: Katsuya
authors.initials: K
authors.lastname: Imanishi
authors.affiliation: Fukuoka i3-Center for Organic Photonics and Electronics Research (i3-OPERA), 5-14 Kyudai-shinmachi, Nishi, Fukuoka 819-0388, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Yukiwaki
authors.affiliation: Osaka Laboratory, Sumika Chemical Analysis Service, Ltd. (SCAS), 1-135, Kasugade-Naka 3-chome, Konohana-ku, Osaka, 554-0022, Japan.
authors.forename: Hong
authors.initials: H
authors.lastname: Wei
authors.affiliation: Fukuoka i3-Center for Organic Photonics and Electronics Research (i3-OPERA), 5-14 Kyudai-shinmachi, Nishi, Fukuoka 819-0388, Japan.
authors.forename: Kaori
authors.initials: K
authors.lastname: Nagayoshi
authors.affiliation: Fukuoka i3-Center for Organic Photonics and Electronics Research (i3-OPERA), 5-14 Kyudai-shinmachi, Nishi, Fukuoka 819-0388, Japan.|Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan.|Institute of System, Information Technology and Nanotechnology (ISIT), 2-1-22 Momochihama, Sawara, Fukuoka 819-0395, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Yahiro
authors.affiliation: Fukuoka i3-Center for Organic Photonics and Electronics Research (i3-OPERA), 5-14 Kyudai-shinmachi, Nishi, Fukuoka 819-0388, Japan.|Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan.|Institute of System, Information Technology and Nanotechnology (ISIT), 2-1-22 Momochihama, Sawara, Fukuoka 819-0395, Japan.|Japan Science and Technology Agency (JST), ERATO, Adachi Molecular Exciton Engineering Project, Fukuoka 819-0395, Japan.|International Institute for Carbon Neutral Energy Research (WPI-I2CNER), Kyushu University, 744 Motooka, Nishi, Fukuoka 819-0395, Japan.
authors.forename: Chihaya
authors.initials: C
authors.lastname: Adachi