Kimitaka Keya
Kyushu University
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Publication
Featured researches published by Kimitaka Keya.
Japanese Journal of Applied Physics | 2016
Susumu Toko; Yoshihiro Torigoe; Kimitaka Keya; Hyunwoong Seo; Naho Itagaki; Kazunori Koga; Masaharu Shiratani
The suppression of cluster incorporation into a-Si:H films is the key to better film stability, because incorporated clusters contribute to the formation of SiH2 bonds and hence lead to light-induced degradation of the films. To deposit stable a-Si:H solar cells at a high deposition rate (DR), we studied the effects of the gas flow rate on DR and the number of Si clusters incorporated into a-Si:H films with discharge power as a parameter, using a multihollow discharge-plasma chemical vapor deposition method. We succeeded in depositing high-quality a-Si:H films with the incorporation of few clusters at DR of 0.1 nm/s. We also found that, under a low gas flow rate and a high discharge power, high-density clusters exist in plasma and hence DR is reduced as a result of radical loss to the clusters.
Japanese Journal of Applied Physics | 2016
Kimitaka Keya; Takashi Kojima; Yoshihiro Torigoe; Susumu Toko; Daisuke Yamashita; Hyunwoong Seo; Naho Itagaki; Kazunori Koga; Masaharu Shiratani
We have measured the hydrogen content ratio I SiH2/I SiH associated with Si–H2 and Si–H bonds in p–i–n (PIN) a-Si:H solar cells by Raman spectroscopy. With decreasing I SiH2/I SiH, the efficiency, short-circuit current density, open-circuit voltage, and fill factor of PIN a-Si:H solar cells after light soaking tend to increase. Namely, I SiH2/I SiH correlates well with light-induced degradation of the cells. While a single I-layer has a low I SiH2/I SiH of 0.03–0.09, a PIN cell has I SiH2/I SiH = 0.18 because many Si–H2 bonds exist in the P-layer and at the P/I interface of the PIN solar cells. To realize PIN solar cells with higher stability, we must suppress Si–H2 bond formation in the P-layer and at the P/I interface.
The Japan Society of Applied Physics | 2017
Susumu Toko; Kazuma Tanaka; Takashi Kojima; Kimitaka Keya; Daisuke Yamashita; Hyunwoong Seo; Naho Itagaki; Kazunori Koga; Masaharu Shiratani
The Japan Society of Applied Physics | 2017
Susumu Toko; Takashi Kojima; Kimitaka Keya; Kazuma Tanaka; H Seo; Naho Itagaki; Kazunori Koga; Masaharu Shiratani
Surface & Coatings Technology | 2017
Susumu Toko; Yoshihiro Torigoe; Kimitaka Keya; Takashi Kojima; Hyunwoong Seo; Naho Itagaki; Kazunori Koga; Masaharu Shiratani
応用物理学会九州支部学術講演会講演予稿集(Web) | 2016
T Kojima; Susumu Toko; Kimitaka Keya; H Seo; Naho Itagaki; K. Koga; Masaharu Shiratani
The Japan Society of Applied Physics | 2016
Takashi Kojima; Susumu Toko; Kimitaka Keya; Kazumaa Tanaka; H Seo; Naho Itagaki; Kazunori Koga; Masaharu Shiratani
The Japan Society of Applied Physics | 2016
Kimitaka Keya; Kazuma Tanaka; Takashi Kojima; Susumu Toko; Daisuke Yamashita; Hyunwoong Seo; Nao Itagaki; Kazunori Koga; Masaharu Shiratani
Japanese Journal of Applied Physics | 2016
Kimitaka Keya; Takashi Kojima; Yoshihiro Torigoe; Susumu Toko; Daisuke Yamashita; Hyunwoong Seo; Naho Itagaki; Kazunori Koga; Masaharu Shiratani
Bulletin of the American Physical Society | 2015
Yoshihiro Torigoe; Kimitaka Keya; Susumu Toko; Hyunwoong Seo; Haho Itagaki; Kazunori Koga; Masaharu Shiratani