Photoelectric and spectral properties of ZnO thin films

An optimization of transparent conductive coatings to increase efficiency is very important for solar cell applications. The developed technique has allowed to obtain both transparent high conductive and dielectric ZnO films doped by different impurities. Measurements of dark and photoconductivity were carried out in a wide frequency range. Photoelectric property studies have shown that with Li doping it is possible to achieve a significant increase of the photoconductivity. The current-voltage characteristics, current-optical power sensitivity and kinetics of rise and decay times of slow and fast components of the photoresponse were studied. It was found that the dark current and photocurrent in Li doped ZnO films have different conductivity mechanisms: hopping mechanism or charge transfer in a Hubbard-model impurity band for dark conductivity current, and drift mechanism of charge transfer in the conduction band for photoconductivity current.