Growth and properties of lead iodide thin films by spin coating

Abstract

In this study, lead iodide (PbI2) thin films were deposited on glass substrates by spin coating a solution of 0.2 M PbI2 dissolved in dimethylformamide, varying the deposition time and the spin speed. The thickness of the thin films decreased with increase in spin speed and deposition time, as examined by profilometry measurements. The structure, morphology, optical and electrical properties of the thin films were analysed using various techniques. X-ray diffraction patterns revealed that the thin films possessed hexagonal structures. The thin films were grown highly oriented to [001] direction of the hexagonal lattice. Raman peaks detected at 96 and 136 cm−1 were corresponding to the characteristic vibration modes of PbI2. The X-ray photoelectron spectroscopy detected the presence of Pb and I with core level binding energies corresponding to that in PbI2. Atomic force microcopy showed smooth and compact morphology of the thin films. From UV–Vis transmittance and reflectance spectral analysis, the bandgap of the thin films ∼2.3 eV was evaluated. The dark conductivity of the thin films was computed and the value decreased as the deposition time and spin speed increased.