Another possibility is that direct recombination within the pulse is still active after the pulse, but our fitting with a time-independent residue does not support this interpretation. In any case, an intricate numerical model seems necessary to fully resolve this question. It is noteworthy that upon sulfur treatment, the decay of the fast process is decelerated, indicating a slower loss of mobile charge carriers. The reason can be that the sulfur treatment reduces trap states or recombination.