Physical modeling of the electrical properties of PbI2 films

PbI2 polycrystalline films were grown on glass substrates with an indium-tin-oxide coating by a physical vapor deposition method using PbI2 raw materials purified by a zone refining technique.Numerous dark current–voltage, dark current–temperature, and dark current–time measurements were taken to study the bulk and surface electrical properties of the film. The impurity level which is responsible for dark current behavior of PbI2 films, Ea=0.79±0.11 eV in energy gap, was calculated from dark current–temperature dependencies. The motions of ions (impurities) determine a film's dark bulk and surface conductivity. The suggested polarization model, based on orientational polarization explains the films dark current decay over time. A surface defects model, which attributes the film's surface as the source and sink of defects, describes the features of PbI2 films I–V curves behavior. These physical hypotheses are in good agreement with currently available experimental data. The instability of the measured film's properties is determined by surface morphology that leads to the immense free surface of PbI2 films.