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We have fabricated high-efficiency a-Si/µc-Si tandem solar cells and modules with a very high µc-Si deposition rate using Localized Plasma Confinement CVD to give very high-rate deposition (>2.0 nm/s) of device-grade µc-Si layers. For further progress in productive plasma-CVD techniques, we have studied plasma phenomena by combining newly developed plasma simulation and plasma diagnosis techniques that reveal the importance of non-emissive atomic hydrogen. We also have proposed a model of defective µc-Si formation on highly textured substrates in which the atomic H in plasma is assumed to play an important role. We are also developing a non-vacuum deposition technique that we term “Liquid Si Printing.” A new record conversion efficiency for HIT solar cells of 24.7% has been achieved using a very thin c-Si wafer (Thickness: 98 µm, Area: 102 cm2).

The aggregation of dyes in an aqueous or alcoholic solution has been studied spectroscopically by a method named the "maximum slope method."The method can ascertain the molar absorptivity and formation constant of dye aggregate when a simple equilibrium model between a monomer and an n-mer is assumed to be operative, and when the absorptivity of monomer is given.Further, the molar absorptivities of the monomer and the polymers and the formation constants of the polymers are adjusted, in order to minimize the mean deviation, by an other method, named the "minimum deviation method." Using the latter method, the parameters of an equilibrium system including a monomer and several polymers can also be calculated.Aggregations of Benzopurprine 4B and Sky Blue FF in aqueous salt solutions were studied by the above two methods.Aggregations of these dyes in aqueous alcoholic solutions were also discussed.

The film properties and solar cell performances of hydrogenated amorphous silicon (a-Si:H) fabricated by a newly developed non-vacuum process "Liquid-Si printing method" were systematically investigated by comparing to the conventional plasma-chemical vapor deposition method. The as-printed a-Si:H films showed relatively high Urbach-tail characteristic energy (E ch ), high [Si-H 2 ]/[Si-H], and low photoconductivity (~10 −7 S/cm). However, the [Si-H 2 ]/[Si-H] decreased, and the photoconductivity was improved to the device grade level (~10 −5 S/cm) after appropriate catalytic-generated atomic hydrogen treatment. It was also found that the light-induced degradation of the photoconductivity and solar cell efficiency of the printed samples were less than half of the conventional a-Si:H case.