Suppressing Charge Recombination in DSSCs with ZrO2 Compact Layers: Experimental Validation and Mathematical Modeling

Since their breakthrough development, dye-sensitized solar cells (DSSCs) have emerged as highly promising third-generation photovoltaics; however, interfacial charge carrier recombination remains a persistent bottleneck. This study investigates the application of a wide bandgap ZrO2 electron blocking layer (EBL) to mitigate this recombination. A 48 nm ZrO2 EBL was deposited on fluorine-doped tin oxide (FTO) via hydrothermal treatment. Empirical results demonstrate a remarkable 43.9% enhancement in overall power conversion efficiency (6.77%) and a 69% improvement in total Incident Photon-to-Current Efficiency (IPCE) compared to bare FTO architectures. To theoretically validate the role of an insulating material as an EBL, the empirical data is supported by mathematical modeling, specifically utilizing Wentzel–Kramers–Brillouin (WKB) quantum tunneling probabilities and 1D diffusion–recombination kinetics. The models confirm that at nanoscale thicknesses, ZrO2 acts as a selective physical barrier that shifts the surface Fermi level and extends the electron lifetime to 0.0146 s. Furthermore, potential optimization pathways utilizing machine learning algorithms for ideal thickness prediction and IPCE clustering are discussed, paving the way for next-generation predictive device engineering. Ultimately, this dual empirical–theoretical approach provides a comprehensive understanding of the interfacial charge transport mechanisms, establishing a robust framework for designing highly efficient, leak-free photoanode architectures in next-generation photovoltaics.