Temperature dependence of the optical absorption coefficient of microcrystalline silicon

The optical absorption coefficient of amorphous and microcrystalline silicon was determined in a spectral range 400–3100 nm and a temperature range 77–350 K. Transmittance measurement and Fourier transform photocurrent spectroscopy were used. The measured data served as an input for our optical model of amorphous/microcrystalline tandem solar cell. Differences in the current generated in the amorphous and microcrystalline parts were computed, for an operating temperature between −20 °C and +80 °C. Optical spectra of microcrystalline silicon were compared to the spectrum of silicon on sapphire (without hydrogen and hydrogenated) and the observed difference was interpreted in terms of a different density of defects and higher disorder of microcrystalline Si.