Influence of solution rate and substrate temperature on the properties of lead iodide films deposited by spray pyrolysis

Polycrystalline lead iodide (PbI₂) thin films have been deposited by spray pyrolysis method using N,N-dimethylformamide (DMF) as solvent as a function of several deposition parameters. DMF is used as an alternative to water due to the larger solubility limit of PbI₂ in this solvent. In this work, the solution rate during the deposition time of 3 h was varied in the range of 0.11 cm³/min up to 0.30 cm³/min. A growth rate varying from 19 Å s⁻¹ up to 47 Å s⁻¹ was obtained as a function of solution rate. Dark current as a function of temperature for the final films reveals that for larger solution rates smaller values of electrical resistivity is obtained. For a solution rate of 0.30 cm³/min, an electrical transport activation energy (E _a) of about 0.65 eV was measured for the whole temperature range. On the other hand, for the sample deposited with a solution rate of 0.11 cm³/min, two main transport mechanisms can be observed with an activation energy of about 1.23 eV for temperatures above 50 °C. The effect of substrate temperature is also discussed. Samples were deposited in the temperature range of 170 °C up to 250 °C with a fixed solution rate of 0.16 cm³/min. In addition, the films were exposed to X-ray irradiation in the mammography diagnosis region, using a molybdenum (Mo) anode and a peak tube potential between 26 and 36 kV (equivalent photon energies between 10 keV and 15 keV).