<p>Heterojunction solar cells (HSCs) prepared on <i>n</i>-Si and organic materials have attracted momentous attention due to their cost-effectiveness and potential for high efficiency. HSCs feature thin amorphous silicon layers deposited on crystalline silicon wafers, with metal contacts separated from the absorber by a wider bandgap layer. However, charge recombination at the rear interface remains a critical challenge that hinders their power conversion efficiency (PCE). Previous studies utilizing materials such as TiO₂ and ZnS to enhance the efficiency of HSCs have been limited by issues related to the Schottky barrier and contact resistance, which hinder their overall performance. The present study introduces a novel approach to enhance HSC performance by incorporating a zinc oxide (ZnO) thin layer at the rear interface using a low-temperature, spin-coating technique. The results demonstrate that the ZnO layer effectively reduces the Schottky barrier and contact resistance, leading to considerable suppression of charge recombination, as confirmed by measurements of minority carrier lifetime, electrochemical impedance spectroscopy, and external quantum efficiency. The optimized device achieved a PCE of 13.7% and a <i>V</i>_oc of 0.603&#xa0;V, indicating significant performance improvement. The improvement is based on the idea that a ZnO layer can modify the interface properties reducing barriers and resistance, thereby facilitating better charge collection and reducing recombination, leading to higher efficiency. Future work will focus on further optimizing the ZnO layer thickness and exploring additional interface modifications to enhance efficiency and stability, ultimately facilitating the implementation of these findings in commercial solar cell applications.</p>