In this study, we designed a packaging process for organic photovoltaics (OPVs) using an ultraviolet-curable polymer encapsulant for improved stability against oxidation. We investigated the chemical and physical properties of polyurethane acrylates (PUA) without reactive diluents, PUA with 2-hydroxyethyl methacrylate (PUA-HEMA), and PUA with 2,2,2-trifluoroethyl methacrylate (PUA-TFMA) through Fourier-transform infrared spectroscopy, X-ray diffraction analysis, and differential scanning calorimetry. Among the three types of resins, PUA-HEMA provided the most effective oxygen barrier and possessed improved mechanical properties. These desirable properties originated from strong intermolecular packing induced by hydrogen bonding between hydroxyl groups in HEMA segments. Because of its advantages, PUA-HEMA was adopted as the encapsulant in the packaging process for OPVs. We confirmed the anti-oxidation behaviour and the resulting OPV performance through various analyses. The PUA-HEMA encapsulant allowed long-term OPV operation by preventing the corrosion of aluminum electrodes in ambient air.