Abstract: The rapid advancement of micro-electro-mechanical system (MEMS) has imposed increasingly stringent demands on integrated energy devices, particularly in terms of miniaturization, long operational lifetime, and high structural and operational stability. In this context, radioisotope photovoltaic batteries have attracted sustained interest as long-lived power sources capable of operating in environments where conventional energy harvesting technologies are ineffective. However, despite their high radiation tolerance and technological maturity, traditional inorganic radiophotovoltaic isotope batteries remain fundamentally limited by their rigid device architectures, complex and energy-intensive fabrication processes, and insufficient spectral compatibility with the narrowband and extremely low-intensity radioluminescence emitted by tritium-based light sources. These intrinsic constraints significantly hinder their application in flexible, lightweight, and weak-light energy harvesting systems required for next-generation MEMS and self-powered microsystems. To address these challenges, this study proposed an alternative material and device strategy for radiophotovoltaic isotope batteries based on wide-bandgap organic photovoltaic (OPV) materials. Owing to their tunable absorption spectra, solution processability, low cost and compatibility with flexible and miniaturized device architectures, wide-bandgap organic semiconductors provide a promising pathway for enhancing spectral matching with radioluminescent sources while maintaining structural adaptability. In this work, particular emphasis was placed on the narrowband and ultra-weak emission characteristics of a ³H/ZnS∶Cu tritium radioluminescence source. Two representative wide-bandgap non-fullerene OPV systems, namely PM6∶Y6 and D18∶L8-BO, were fabricated and systematically investigated as active layers for radiophotovoltaic energy conversion. Device performances were evaluated under both standard AM1.5G solar illumination and radioluminescent excitation from the ³H/ZnS∶Cu source, enabling a direct comparison of their photovoltaic behaviors across vastly different photon flux regimes. The experimental results demonstrate that wide-bandgap organic systems exhibit pronounced advantages in radioluminescence-driven energy harvesting. Under an ultra-low irradiance of 8.00×10⁻⁴ mW/cm² provided by the ³H/ZnS∶Cu tritium source, the PM6∶Y6 device achieves a power conversion efficiency of 16.03%. More notably, the D18∶L8-BO device, benefiting from superior optical absorption capability and enhanced spectral matching with the dominant radioluminescent emission peak, delivers an output power density of 1.32×10⁻⁴ mW/cm² and achieves a conversion efficiency of 16.51%. Based on this organic photovoltaic system, the overall efficiency of the constructed radiophotovoltaic isotope battery reaches 1.52%. These findings clearly indicate that precise alignment between the absorption spectrum of the organic active layer and the emission profile of radioluminescent sources is a critical factor for improving photoelectric conversion efficiency under ultra-weak light conditions. In addition to spectral compatibility, organic semiconductors exhibit stable built-in electric field utilization under low photon flux, along with inherent advantages including low material cost, mechanical flexibility, and suitability for scalable and miniaturized fabrication. Collectively, these attributes render organic photovoltaic materials highly competitive alternatives to conventional inorganic systems for radiophotovoltaic isotope batteries. As experimentally validated in this study, the D18∶L8-BO system emerges as one of the most promising organic active layer candidates for tritium-driven radiophotovoltaic applications. Overall, the incorporation of wide-bandgap organic photovoltaic materials provides a viable and effective technological route for powering MEMS, self-sustained microsystems, and flexible energy devices, offering critical material solutions and design strategies for overcoming the spectral and structural limitations inherent to traditional inorganic radiovoltaic technologies.