Nebulizer-assisted spray deposited Mn3O4 films: Study the substrate temperature influenced electrochromic properties cycled in neutral aqueous electrolyte system

Abstract

In this work, we report the impact of substrate temperature effect on the electrochromic characteristics of trimanganese tetraoxide (Mn3O4) films prepared by nebulizer-assisted simple spray pyrolysis technique. The deposited films are in tetragonal Mn3O4 crystal-phase as realized by XRD study. The A1g, T2g and Eg Raman active modes of spinel-Mn3O4 phase are observed well in micro-Raman study. The electronic states and surface topology of the deposited Mn3O4 films were examined by XPS and FE-SEM analyses. From the optical study, the blue shift in transmittance edges and the systematic improvement of optical band gap are visualized when increasing the substrate temperature. The electrochromic performance of deposited samples was examined in 0.5 M Na2SO4 neutral aqueous system at room temperature. This neutral electrolyte offers lesser H+ and OH− concentrations and low corrosion effect, which make the window potential range wider. The optical blue-shift was observed in maximum peak positions of electrochromic parameters. The obtained result revealed that the amorphous films have superior electrochromic behavior than the crystalline one. The sample prepared at 350°C substrate temperature reaches a maximum absorbance modulation efficiency (AMEm (CEm)) of 9.626 cm2/C (at 431.61 nm), whereas, after the 100th cycle, the AMEm value increases from 9.626 to 11.154 cm2/C.