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Effect of halogenated impurities on lifetime of organic light emitting diode
Author(s): Hayato Yamawaki; Kunihiko Suzuki; Tomohiro Kubota; Takeyoshi Watabe; Ayumi Ishigaki; Rina Nakamura; Hideko Inoue; Harue Nakashima; Nozomi Horikoshi; Hiromi Nowatari; Riho Kataishi; Toshiki Hamada; Toshiki Sasaki; Tsunenori Suzuki; Satoshi Seo
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Paper Abstract

We investigated a correlation between lifetime and the halogen element concentration in an organic light-emitting diode (OLED) and conducted experiments and simulations to discuss degradation mechanisms due to the halogen. OELD is generally formed of high-purity materials. Since the synthesis of high-purity materials takes time and cost, quantitative understanding of the kind, amount, and influence of impurities in OLED devices is expected. The results of combustion ion chromatography show that, if the chlorine concentration in the host material is more than several parts per million, the lifetime of the device is drastically reduced. The chlorine element, which is derived from the chlorinated by-product of the host material, is found to be transferred from the chloride to other materials (e.g., an emissive dopant) according to the results of LC-MS analysis. In addition, the electron transport layer including such impurities is also found to adversely affect the lifetime. The results of TOF-SIMS analysis suggest that the dissociated chlorine element diffuse to the light-emitting layer side when the device is driven. The results of simulations (Gaussian 09) and electrochemical analyses (cyclic voltammetry and electrolysis) reveal that the halogen element is easy to dissociate from halide by excitation or reduction. The halogen element can repeat reactions with the peripheral materials by excitation or reduction and cause damages, e.g., generate radicals or further reaction products due to the radicals. The results of simulation suggest that, such compounds have low energy level and become quenchers.

Paper Details

Date Published: 23 September 2016
PDF: 15 pages
Proc. SPIE 9941, Organic Light Emitting Materials and Devices XX, 99410P (23 September 2016); doi: 10.1117/12.2237544
Show Author Affiliations
Hayato Yamawaki, Semiconductor Energy Lab. Co., Ltd. (Japan)
Kunihiko Suzuki, Semiconductor Energy Lab. Co., Ltd. (Japan)
Tomohiro Kubota, Semiconductor Energy Lab. Co., Ltd. (Japan)
Takeyoshi Watabe, Semiconductor Energy Lab. Co., Ltd. (Japan)
Ayumi Ishigaki, Semiconductor Energy Lab. Co., Ltd. (Japan)
Rina Nakamura, Semiconductor Energy Lab. Co., Ltd. (Japan)
Hideko Inoue, Semiconductor Energy Lab. Co., Ltd. (Japan)
Harue Nakashima, Semiconductor Energy Lab. Co., Ltd. (Japan)
Nozomi Horikoshi, Semiconductor Energy Lab. Co., Ltd. (Japan)
Hiromi Nowatari, Semiconductor Energy Lab. Co., Ltd. (Japan)
Riho Kataishi, Semiconductor Energy Lab. Co., Ltd. (Japan)
Toshiki Hamada, Semiconductor Energy Lab. Co., Ltd. (Japan)
Toshiki Sasaki, Semiconductor Energy Lab. Co., Ltd. (Japan)
Tsunenori Suzuki, Semiconductor Energy Lab. Co., Ltd. (Japan)
Satoshi Seo, Semiconductor Energy Lab. Co., Ltd. (Japan)


Published in SPIE Proceedings Vol. 9941:
Organic Light Emitting Materials and Devices XX
Franky So; Chihaya Adachi; Jang-Joo Kim, Editor(s)

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