Time-Resolved Investigation of PhotocurrentRelaxation in Ionic Conductor Beta-AgI forDifferent Temperatures

Time-resolved measurements of photoirradiation effects provide an intimate understanding of the processes involved in photoexcited systems. In this work, we measured time-resolved photocurrents of KI-treated -AgI polycrystals, which provide information about the primary process underlying the photoinduced change in the ionic conductivity of -AgI. Two excitation wavelengths, 450 nm and 532 nm, corresponding to excitation at the band-gap edge and in the sub-band-gap region, respectively, were used to photoirradiate the samples. The transient photocurrents measured by shining -AgI pellets with a nanosecond pulsed laser show fast and slow decay components in the nanosecond and microsecond time regions at both room temperature (298 K) and liquid nitrogen temperature (77 K). The remarkable photocurrent observed at room temperature was significantly suppressed at 77 K. The photocurrent relaxation also showed a clear temperature dependence: the photocurrent relaxation time (the averaged decay time) observed at room temperature was in the range of 2-3 s, while a faster photocurrent relaxation in the range of 0.3-0.4 s was observed at 77 K. Although the decrease in average relaxation time at 77 K does not represent a uniform decrease across all relaxation processes, the component 3 (3) process shows a significant increase at 77 K compared to 298 K.