Determination of the Density of States in Semiconductors from Transient Photoconductivity

This paper discusses the techniques we have developed to analyse the photo-response of amorphous semiconductors to transient optical excitation to determine the energy distribution of gap states (DOS). We highlight the difficulties arising from a direct ‘single point’ approach using the instantaneous transient photocurrent i(t) when there is significant structure in the DOS or in the presence of recombination. Frequency domain methods which …