Proportionality between Photoconductance and Time Constant in Lead Sulfide Films

Relative humidity variation, aging, vacuum overcoating, and background light change the signal, the resistance, and the time constant of lead sulfide films at room temperature. Yet the relative change in photoconductance is proportional to the relative change in time constant. This result is taken as evidence that the time constant of photoconductivity is identical to the lifetime of the holes. It is shown that the ratio of signal to the product of resistance and time constant is useful in interpreting data taken on films whose properties are changed by ambient conditions.