403 citations · 1k across the 11 of their papers we have counts for
11 papers
Fully automated spectroscopic ellipsometry analyses of crystalline-phase semiconductors based on a new algorithm
Sara Maeda, Kohei Oiwake, Yukinori Nishigaki +8
One significant drawback of a spectroscopic ellipsometry (SE) technique is its time-consuming and often complicated analysis procedure necessary to assess the optical functions of…
Fully automated spectroscopic ellipsometry analyses: Application to MoOx thin films
Kohei Oiwake, Yukinori Nishigaki, Shohei Fujimoto +2
In spectroscopic ellipsometry, the optical properties of materials are obtained indirectly by generally assuming dielectric function and optical models. This ellipsometry analysis,…
Highly accurate prediction of material optical properties based on density functional theory
Mitsutoshi Nishiwaki, Hiroyuki Fujiwara
Theoretical material investigation based on density functional theory (DFT) has been a breakthrough in the last century. Nevertheless, the optical properties calculated by DFT gene…
Giant oscillator strength in the band-edge light absorption of zincblende, chalcopyrite and kesterite solar cell materials
Masato Kato, Mitsutoshi Nishiwaki, Hiroyuki Fujiwara
In semiconducting solar-cell absorbers, high absorption coefficient (alpha) near the band-edge region is critical to maximize the photocurrent generation and collection. Neverthele…
Maximum efficiencies and performance limiting factors of inorganic and hybrid perovskite solar cells
Yoshitsune Kato, Shohei Fujimoto, Masayuki Kozawa +1
The Shockley and Queisser limit, a well-known efficiency limit for a solar cell, is based on unrealistic physical assumptions and its maximum limit is seriously overestimated. To u…
Tail state formation in solar cell materials: First principles analyses of zincblende, chalcopyrite, kesterite and hybrid perovskite crystals
Mitsutoshi Nishiwaki, Keisuke Nagaya, Masato Kato +6
Tail state formation in solar cell absorbers leads to a detrimental effect on solar cell performance. Nevertheless, the characterization of the band tailing in experimental semicon…
Carrier loss mechanisms in textured crystalline Si-based solar cells
Akihiro Nakane, Shohei Fujimoto, Hiroyuki Fujiwara
A quite general device analysis method that allows the direct evaluation of optical and recombination losses in crystalline silicon (c-Si)-based solar cells has been developed. By…
Universal rules for visible-light absorption in hybrid perovskite materials
Masato Kato, Takemasa Fujiseki, Tetsuhiko Miyadera +5
A variety of organic-inorganic hybrid perovskites (APbX3) consisting of mixed center cations [A = CH3NH3+, HC(NH2)2+, Cs+] with different PbX3- cages (X = I, Br, Cl) have been deve…
Quantitative determination of optical and recombination losses in thin-film photovoltaic devices based on external quantum efficiency analysis
Akihiro Nakane, Hitoshi Tampo, Masato Tamakoshi +6
In developing photovoltaic devices with high efficiencies, quantitative determination of the carrier loss is crucial. In conventional solar-cell characterization techniques, howeve…
Degradation mechanism of CH3NH3PbI3 perovskite materials upon exposure to humid air
Masaki Shirayama, Masato Kato, Tetsuhiko Miyadera +7
Low stability of organic-inorganic perovskite (CH3NH3PbI3) solar cells in humid air environments is a serious drawback which could limit practical application of this material seve…
Optical transitions in hybrid perovskite solar cells: Ellipsometry, density functional theory, and quantum efficiency analyses for CH3NH3PbI3
Masaki Shirayama, Hideyuki Kadowaki, Tetsuhiko Miyadera +10
We report artifact-free CH3NH3PbI3 optical constants extracted from ultra-smooth perovskite layers without air exposure and assign all the optical transitions in the visible/ultrav…