Photoacoustic spectroscopy of photovoltaic materials

A photoacoustic spectrometer is described which has been constructed to measure the spectra of photovoltaic materials in the ultra violet, visible and near infra red regions. The range of this photoacoustic spectrometer is from 0.3 to 1.8 mu m. This technique has the advantage of being non-intrusive and non-destructive. Measurements have been made of a variety of photovoltaic materials, including a CdS/CuIn1-zGazSe2 heterojunction and an InP/InGaAsP quantum well layer system. Bands arising from intrinsic impurity subgap levels were observed beyond the band edges.