Band gap energy comparison of lead iodide excited by an Nd:YAG laser

Photon density versus charge (( I p versus Q ))/lux–ampere characteristics of PbI2 single crystals have been studied by using fundamental and frequency-doubled Nd:YAG lasers. The results are compared with those of similar photoconductivity studies of ZnS and CdI2 crystals. The studies show the involvement of the Franck–Condon principle-process-effect rather than opposite parity valence bands for the appearance of two different frequencies: one in the case of photoluminescence/photoacoustics and the other in the case of transmittance/photoconductivity.