The optical absorption coefficient α of doped and undoped hydrogenated amorphous silicon (a-Si:H) has been measured for photon energies from 2.2 to 1.0 eV using photo-pyroelectric spectroscopy (PPES). A simplified experimental setup and analysis for extracting α from the PPES data are described. In PPES the temperature rise induced in the a-Si:H thin film due to weakly absorbed light is detected via a pyroelectric polymer in thermal contact with the sample. This technique presently has a sensitivity of αd≳10-3, where d is the sample thickness.
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