Transient Photoinduced Absorption Research Articles

Effects of recombination on trap-limited dispersive transport

The effects of monomolecular and bimolecular recombination on dispersive transport for a system with an exponential distribution of traps have been simulated using a Monte Carlo technique. Both the concentration of photo-excited carriers and the photocurrent fall off similarly for the two recombination modes, although the overall decay is somewhat slower for the bimolecular process. In each mode, the carrier concentration exhibits a power-law decay at long times, with the exponent proportional to the absolute temperature. We conclude that transient photoconductivity and photo-induced absorption measurements cannot determine the predominant recombination kinetics without a study of the dependence of the results on the incident light intensity. Furthermore, if the recombination mode is unknown, the conventional approach can give an erroneous result for the extent of the trap distribution.

Photocurrent Transient Spectroscopy: Measurement of the Density of Localized States ina-As2Se3

Measurements of transient photoinduced optical absorption in $a$-${\mathrm{As}}_{2}$${\mathrm{Se}}_{3}$ show that carriers thermalize within a distribution of localized states in the band gap. Photocurrent as well as photoinduced optical absorption transients are explained in a unified way with the multiple-trapping mechanism. Under such circumstances, transient photoconductivity provides a spectroscopy of the density of localized states.