χ-Anderson type polyoxometalates and anhydride based polyimides: Synthesis, characterization and photovoltaic response in dye sensitized solar cells

Abstract

Efficient electron transport and minimizing recombination losses are crucial for optimizing DSSC performance, necessitating strategies to improve electron diffusion and reduce charge recombination. Two new eco-friendly polyimides based on χ-type polyoxometalates namely Tris@ZnPOM, and Tris@NiPOM, one with the Zn-containing Anderson-type POM(ADP), and the other with the Ni-containing Anderson-type POM, respectively have been synthesized and characterized by FT-IR, UV–vis. spectral analysis, TGA,1H NMR, fluorescence and cyclic voltametric analysis. The fluorescence quenching in Tris@ZnPOM, and Tris@NiPOM was observed as98% and 99.7% as compared to Tris@anhydride, referring the photo-induced transfer of electrons between POM and Tris@anhydrides. The dielectric loss is found to be higher in Tris@anhydride as compared to the Tris@NiPOM, and Tris@ZnPOM. From the MEP analysis it has been seen that POM act as an electron with drawing subunit when conjugated with the anhydride. Different global reactivity parameters (μ, η and ω) were estimated from the frontier molecular orbitals (FMO) analysis, and the order of reactivity for Tris@anhydride, Tris@NiPOM, and Tris@ZnPOM is determined to be in accordance with their increasing band gap i.e., Tris@anhydride > Tris@NiPOM > Tris@ZnPOM. The increase in efficiency (η) of photovoltaics response for Tris@ZnPOM (2.35) is found to be higher as compared to Tris@NiPOM (1.25) and Tris@anhydride(0.62). The presence of Zn in ADP is responsible for increasing the efficiency of Tris@ZnPOM due to its low band gap that causes the easiest transfer of electron.