Upon comparing the light intensity dependence of the maximum of the photoconductance signal, it is observed that the TRMC signal is relatively constant at lower light intensities and then decreases with increasing light intensity >10 photons/cm 2 /pulse (Figure ). Based on the slope of the log plot ΦΣμ vs I0 α-1 , the order of the mobile charge carrier loss process could be deduced (where α is the reciprocal of the order of the recombination process). At lower light intensities, the concentration of photogenerated electrons and holes is relatively low and trapping is the dominant loss process for mobile charge carriers. At light intensities above 10 11 photons/cm 2 /pulse α was ~ 0.63, showing that second order recombination dominates. At these increased light intensities, the bands are populated by a high density of photogenerated charge carriers leading to increased second order recombination-probably due to direct electron and hole recombination-and a reduction in the TRMC signal height (Figure ) already during the laser pulse. Moreover, it is interesting to note that the onset for second order recombination occured at lower photon flux in sulfur-treated films (as indicated by extrapolation in Figure ). The explanation for this phenomenon is that the sulfur treatment reduces the amount of defect/trap states, which enables the accumulation of a higher concentration of photogenerated charge carriers in the bands at lower laser intensities as compared to the untreated sample. Therefore, the second order recombination process sets in at a lower light intensity. Usually, the TRMC decays are either fitted with a single or a double exponential function.