<p>Graphene–silicon (Gr–Si) Schottky heterojunction solar cells provide a promising solution for radiation-tolerant and efficient photovoltaic devices. The present study provides the combined predictive modelling and physical characterization to evaluate the degradation assessment of Gr–Si solar cells. The results show Gr–Si devices successfully retain over 84% of their original power conversion efficiency (PCE) at a radiation intensity in terms of fluence in the order of 10¹⁵ particles cm⁻², compared to only 55% for silicon cells alone. X-ray diffraction (XRD), Raman spectroscopy, and Atom Probe Tomography (APT) showed that graphene retains the interface integrity and is efficient in suppressing radiation-induced imperfections. A physics-informed semi-empirical digital twin (DT) assessment carried out using synthetic degradation datasets and Random Forest Regression, performing prediction efficiency above 96% (R² &gt; 0.96). Degradation mathematical models were also formulated to describe the characteristics of open-circuit voltage (V_oc), short-circuit current density ​(J_sc)​, Fill Factor (FF), and Power Conversion Efficiency (PCE) for defined duration. The experimental validation and machine learning combined assessment provides a robust methodology for real-time monitoring and life-cycle prediction of photovoltaic devices in rich-radiation environments.</p>