Growth mechanism, structure, stoichiometry and optical properties of electrochemically grown iron selenide and ferroselite thin films

[Display omitted] •Thin films of wurtzite FeSe and ferroselite FeSe2 with stoichiometry was deposited by simple, low temperature process.•The film at 30 and 70 °C have crystallinity without post annealing process at higher temperature.•Thickness of all the deposited film was found to be in the range 800 nm and 1500 nm.•The estimated band gap value was found to be ‘1.26 and 1.07 eV for FeSe and FeSe2 thin films deposited films at 70 °C. In this present work, FeSe and FeSe2 thin films were deposited on ITO substrate at different electrolytic bath temperatures at 30 °C and 70 °C by using electrodeposition method. The growth mechanism was investigated via cyclic voltammetry with the potential window was found to be −1600 to 1600 mV versus SCE and the formation of well adherent film was found to be higher bath temperature. XRD result shows the deposited FeSe and FeSe2 films found to exhibit stoichiometric wurtzite and orthorhombic phases respectively. The microscopic observation shows, the uniform particle growth of FeSe and FeSe2 was found to be higher electrolytic bath temperature at 70 °C. The EDX analysis shows the deposited FeSe and FeSe2 films at higher temperature elemental is stoichiometric ratio. The determined bandgap values for FeSe (1.26 eV) and FeSe2 (1.07 eV) deposited at 70 °C. Also, we observed that the refractive indices (n) values was increased for the film deposited from 30 °C to 70 °C resulting, the estimated refractive indices (n) for FeSe and FeSe2 are 3.16 and 3.45 respectively. Furthermore the most significant optical parameters extinction coefficient (k), optical conductivity (σoptical), real (Ɛ1) and imaginary (Ɛ1) dielectric constants and dissipation factor (tan δ) are determined in order to investigate their usefulness in photovoltaic applications.