Dye-sensitized solar cells achieved with multi-layered SnO₂/ZnO composite photoanodes through precise control of thickness and composition

The spin coating is cost-effective, straightforward, and highly suitable for the large-scale production of solar cells. In this study, we report the fabrication of SnO₂/ZnO composite films for dye-sensitized solar cells (DSCs) using a simplified and cost-effective spin-coating technique on fluorine-doped tin oxide glass substrates. This study introduces a new way of preparing a multi-layered composite thin film using a suspension containing colloidal SnO₂ nanoparticles and ZnO nanoparticles followed by sonication and aging of TiO₂-free high-efficiency DSCs. Our approach provides a facile way of obtaining a uniform film of tunable thickness with high reproducibility by adjusting the total number of coating cycles. The spin-coating process achieved a nano-sized SnO₂-covered ZnO layer, contributing to enhanced conversion efficiency in DSCs. A specific number of seven coating cycles was identified as optimal for achieving the aspirational performance. Under standard AM 1.5 irradiation with an intensity of 100 mW/ cm², the fabricated SnO₂/ZnO composite films revealed an overall energy conversion efficiency of 6.5% with a thickness of 2.06 µm which is impressive for a TiO₂-free DSC. This achievement indicates the potential of the developed fabrication process for cost-effective and scalable production of efficient DSCs with SnO₂/ZnO composite.