Increasing the electrical anisotropy of solution-grown PbI2 thin films by addition of CdI2

In the present study up to 20% CdI2 has been added to a lead iodide-water solution, which is used to grow PbI2 polycrystalline thin films. As a result, a significant increase in the anisotropy of the lead iodide film's electrical properties has been observed: the resistivity in the direction parallel to the c-axis reached 1015 Ω cm but did not change significantly in the orthogonal direction. This behavior can be explained by the modification of the transport properties related to the crystallographic structure of the films along the c-axis. As suggested by thermally stimulated current measurements, only a small number of the Cd atoms incorporated into the PbI2 lattice could behave as dopants.