It was noted that the techniques of modulated and transient photoconductivity provided useful information concerning the density of traps and defects in the band-gap of semiconductors by using suitable equations to convert the measured data into a density of states. Two cases were considered here which were relevant to photovoltaic materials. These were a discrete set of trap states in the band-gap, and a continuous distribution. Partial occupancy of the states was achieved by the position of the Fermi energy or the quasi-Fermi energy, which resulted in a limitation on the validity of the analysis. Simulation results were also compared with experimental data.

Photoconductivity Techniques for Defect Spectroscopy of Photovoltaic Materials. R.Brüggemann, J.P.Kleider: Thin Solid Films, 2002, 403-404, 30-3