AuNRs attached TiO₂ NPs modified by cobalt-imidazolate frameworks as exceptional materials to improve the energy conversion efficiency of dye-sensitized solar cells

This work reports a significant improvement in both the open-circuit voltage (V_OC) and current density (J) of dye-sensitized solar cells (DSSCs) using gold nanorod-modified TiO₂ nanoparticles (TiO₂/AuNRs) together with a cobalt-imidazolate framework (ZIF-67) as an efficient photoanode. It was demonstrated that adding ZIF-67 (8 wt%) to TiO₂ NPs increased the V_OC by 160 mV and J by 2.5 times. This observation was described based on the significant increase in the amount of adsorbed dye in the presence of highly porous ZIF-67, which boosts the photoanode's light harvesting. Modifying TiO₂ NPs with AuNRs also caused a remarkable enhancement in J (∼ 2.8 times), which can be explained via electron transfer between the TiO₂ conduction band and AuNRs. It can result in a more efficient inhibiting effect on the interfacial charge recombination processes in TiO₂/AuNRs/ZIF-67 because of the formation of a Schottky barrier at the interface between TiO₂ and Au. These effects were confirmed by the reduction in the photoluminescence intensity of TiO₂ in the presence of AuNRs. More reduction in the photoluminescence intensity was observed when ZIF-67 was added. The prepared photoanode showed an outstanding improvement in the overall efficiency of the DSSC (η) to 8.38% compared to the bare TiO₂-based photoanode (1.83%). The notable improvement in the TiO₂/AuNRs/ZIF-67 performance confirmed its practicality for high-efficiency DSSCs.