Title: Combine Influences of Nanoparticulate Hematite Thin Film Thickness, Roughness, and Weight on Its Photoelectrochemical Performance and Viscous/ Thermal Characteristics of Source Precursor

Abstract: The objective of this work was to investigate the photoelectrochemical (PEC) performance of nanoparticulate hematite thin film photoelectrodes prepared by a soft-chemistry route. Two cost-effective thin film fabrication techniques were employed to deposit the hematite film. First, the film was deposited on conducting glass substrates by dip coating of the organic precursor containing fatty acid derivatives of iron salts. Process parameters such as the concentration of iron oleic acid derivative precursor solution, the thickness of the organic film, before annealing and the number of deposited layers along with their weight and roughness were studied. In the second approach, the influence of the spin coating process on film formation and respective photoelectrochemical (PEC) performance have been discussed. It was found that the PEC performance of spin-coated samples was lower than that of dip coated samples due to the effect of films rough and smooth characteristics. It is found that the rough surface of the photoelectrode is a prerequisite to achieving good photocurrent values. Here, three-layer samples with roughness between 600nm to 800nm and bulk thickness up to 700nm provided photocurrent densities of 0.6mA/cm2. In part 2 of the manuscript, we have elaborately discussed the roughness and smooth behavior of thin films using X-ray reflectometry technique. Followed by this, a detailed account of the viscous and thermal properties of the fatty acid derivatives of iron precursor have been discussed.