Spectral Selective Filtering for Thermal Mitigation and Efficiency Enhancement of Crystalline Silicon Photovoltaic Modules under Tropical Climatic Conditions: Experimental Investigation

High solar irradiance during pre-monsoon conditions in tropical regions increases photovoltaic energy generation potential but simultaneously elevates module operating temperature, which adversely affects electrical performance and long-term reliability. Crystalline silicon photovoltaic modules exhibit a negative temperature coefficient of approximately −0.4 to −0.5 %/°C, making thermal management an important consideration for sustained operation. This study experimentally investigates the influence of selective spectral filtering on the thermal and electrical performance of 20 W monocrystalline and polycrystalline photovoltaic modules under natural outdoor conditions in Pune, India (18.9876°N, 73.9651°E). Spectral bands of 400–450 nm, 450–570 nm, 570–750 nm, and 750–1100 nm were evaluated and compared with full-spectrum exposure at 1000 W/m². The 570–750 nm spectral band transmitted 436 W/m² and produced a maximum output power of 15.49 W from the monocrystalline module. Under this condition, a band-limited photon utilization efficiency of 25% was obtained when referenced to the transmitted irradiance. However, this metric differs from conventional photovoltaic conversion efficiency, which is defined using total incident solar irradiance. When referenced to the full incident irradiance of 1000 W/m², the corresponding system-level efficiency was approximately 11.06%, compared with 14.06% under full-spectrum exposure. Selective filtering reduced module surface temperature by approximately 10°C, corresponding to an estimated power retention benefit of about 4.5% based on temperature coefficient analysis. Monocrystalline modules exhibited superior spectral response and lower recombination sensitivity than polycrystalline modules. The results indicate that selective spectral filtering functions primarily as a thermal mitigation and spectral optimization strategy rather than a power enhancement technique. The findings are based on a short-term experimental campaign conducted under pre-monsoon conditions in Pune and should be interpreted within the context of the prevailing seasonal and atmospheric conditions.