Enhanced photovoltaic performance dye-sensitized solar cells (DSSCs) employing α-GeO₂–TiO₂ bilayer and heterojunction photoanodes

In this study the bilayer and binary heterojunction film-based photoanodes were fabricated using α-GeO₂ and anatase-TiO₂ nanoparticles, aiming to explore their photovoltaic capabilities for DSSCs. Results demonstrated that binary TiO₂ – 0.3 wt% GeO₂ heterojunction film based DSSC exhibits the highest PCE of η ∼ 6.244%, accompanied by a current density (J_sc) of 11.570 mA cm^-2 under one sun illumination as compared to bilayer TiO₂ – GeO₂ and TiO₂ film based DSSCs which displayed a PCE of 3.350% and 4.011%, respectively. It should be attributed to α-GeO₂ analogous as a barrier that swift the separation and retard the backward recombination of photogenerated charge carriers at the interfaces of oxidized dye species/redox couple and TiO₂/redox couple, thereby boosting the kinetics of photogenerated electrons. Moreover, α-GeO₂ nanoparticles are expected to function as donors, so the donation of photogenerated electrons from the conduction band (E_CB=-3.5 eV) of α-GeO₂ would enhance the density of electrons in both of LUMO (E_LUMO=-3.8 eV) of N-719 dye molecules and the conduction band (E_CB=-4.28 eV) of anatase-TiO₂. The demonstrated favorable capabilities indicate that α-GeO₂ potentially serves as a viable option for DSSCs.