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Resonant photothermal bending spectroscopy (RPBS) at various measurement temperatures has been developed for estimating absorption coefficient (α) spectra of thin film semiconductors. The experimentally obtained sensitivity of RPBS was about ten times larger than nonresonant PBS. In vacuum, this technique has been applied to estimate the α spectrum of hydrogenated microcrystalline silicon (μc-Si:H) films at the measurement temperatures from 25 to 150 °C. It is demonstrated that the temperature coefficient of an indirect optical absorption at 1.2–1.8 eV caused by Si microcrystallite is almost the same as that of single crystalline silicon, and the temperature coefficient of below-gap absorption intensity is negative. The reason for the negative temperature coefficient and the energy level of the localized state resulting in the below gap absorption are discussed.

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A very high deposition rate for high-quality microcrystalline silicon (lJc-Si) films has been achieved under very high-pressure conditions (> 1,000 Pa) using a Localized Plasma Confinement (LPC)-CVD method which has a special cathode.The uniformity of the IJc-Si film thickness was 2.4% on a 55x65 cm 2 glass substrate with a deposition rate of 2.7 nm/s. We also achieved maximum conversion efficiency of 11.4% for an a-Si/lJc-Si tandem solar cell (1 cm 2 ) on a 20x20 cm 2 glass substrate and average conversion efficiency of 9.84% for a-Si/lJc-Si tandem solar cells (1 cm 2 ) on a 55x65 cm 2 glass substrate with a deposition rate (Rd) of 1.8 nm/s. These results indicate that LPC-CVD method is a good candidate as an effective production technology for large-area, high-performance IJc-Si thin-film solar cells.

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A resonant photothermal bending spectroscopy (PBS) is demonstrated for the measurement of absorption coefficient spectra in hydrogenated microcrystalline silicon (µc-Si:H) and hydrogenated microcrystalline cubic silicon carbide (µc-3C–SiC:H) films. The resonant vibration technique utilized in PBS establishes the sensitivity as αd∼5×10-5 in a vacuum measurement. Appling resonant PBS to µc-Si:H films, a new extra absorption coefficient αex spectrum is observed from 0.6 to 1.2 eV. The αex spectrum has a peak at ∼1.0 eV, and the localized states inducing the αex are located ∼0.35 eV below the conduction band edge of µc-Si:H. A possible explanation for the observed localized state is that an oxidation produces weak bonds at the grain boundaries and/or amorphous silicon tissues. In µc-3C–SiC:H film, an optical band-gap energy of ∼2.2 eV was demonstrated assuming an indirect optical transition. The temperature coefficient of the optical band-gap energy was ∼2.3×10-4 eV K-1. The αex spectrum of µc-3C–SiC:H film is plateau-shaped and its magnitude is in accord with an increase in grain size.