TiO2 Content Effects on Magnetism and Photoresponse in Mn0.25Fe2.75O4/PEG/TiO2 Nanocomposite DSSC Photoelectrodes

Abstract

Fabrication of thin films based on Mn_0.25Fe_2.75O₄/PEG/TiO₂ nanocomposite photoelectrodes was successfully achieved using the doctor blade method. The objective of this study is to evaluate the influence of TiO₂ composition on the magnetic properties and photoresponse of thin films utilizing Mn_0.25Fe_2.75O₄/PEG/TiO₂ nanocomposite photoelectrodes. The crystal structure, functional groups, morphology, and magnetic properties of the Mn_0.25Fe_2.75O₄/PEG/TiO₂ nanocomposites were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and vibrating sample magnetometry (VSM), respectively. Meanwhile, the optical properties and photoresponse of thin films based on Mn_0.25Fe_2.75O₄/PEG/TiO₂ nanocomposite photoelectrodes were investigated using a UV–Vis spectrometer and a photoresponse instrument, respectively. The XRD characterization indicates that the sample consists of cubic spinel (Mn_0.25Fe_2.75O₄) and tetragonal spinel (TiO₂) nanoparticles, with particle sizes of 7.54–10.21 nm and 10.79–14.47 nm, respectively. Based on characterization using TEM, the morphology of the Mn_0.25Fe_2.75O₄/PEG/TiO₂ nanocomposite is spherical, with porous cavities, and the particle sizes range from 10.57 to 13.26 nm. Mn_0.25Fe_2.75O₄/PEG/TiO₂ nanocomposites exhibit superparamagnetic properties, with a saturation magnetization value decreasing from 41.90 to 9.04 emu/g as the TiO₂ nanoparticles increase. That magnetic behavior supports enhanced power conversion efficiency. This is due to the bound magnetic polarons that can absorb dye molecules in DSSC. This result is also consistent with the absorbance of the Mn_0.25Fe_2.75O₄/PEG/TiO₂ nanocomposite, which decreases from 3.69 to 3.28 eV with increasing TiO₂ nanoparticle content. That shift in the band gap enhances photon absorption. The photo-response test results show that the light response time during rise time (τ_r) is 1.53–0.45 s, and the light response time during decay time (τ_d) is 1.01–0.26 s. Based on the result of this report, the faster photoresponse at τ_r = 0.45 s and τ_d = 0.26 s was observed with the higher TiO₂ content in Mn_0.25Fe_2.75O₄/PEG/TiO₂ nanocomposite. That means the relatively fast photo-response time indicates that the Mn_0.25Fe_2.75O₄/PEG/TiO₂ nanocomposite has the potential to serve as a photoelectrodes material that can conduct electron flow quickly.