Carrier recombination in Cu doped CdS thin films: Photocurrent and optical studies

Quenching of photocurrent in Cu doped CdS prepared by Spray pyrolysis technique is reported. Anomalous changes in surface morphology are seen at 2% of Cu in CdS. Surface morphology of pure CdS film shows rod like structure. Aspect ratio of such rods has a maximum around 2% Cu substitution. This in turn produces anomalous changes in photoconductivity, which is further supported by marked changes seen in mean crystallite size, strain and grain size, roughness, transmittance, optical band gap, activation energy and finally in the photocurrent. Pronounced effects are seen in transmittance as a broad profile centered on 590 nm. The observed effects are explained in terms of carrier recombination mechanisms.