A visibly clear radiative cooling film with high sub-bandgap reflectance for enhancing solar cell performance

The performance of solar cells (SCs), including the photoelectric conversion efficiency and lifespan, significantly degrades with increasing operating temperature. Spectral-selective radiators with high visible transparency and strong infrared thermal emission offer a practical way to reduce temperatures and enhance SC performance. However, conventional radiators for SCs generally exhibit high transmittance across the entire solar spectrum (0.38–4.0 μm), thereby failing to reflect sub-bandgap (1.1–4.0 μm) irradiance, which can lead to parasitic heating. Herein, we propose a tri-band modulated film (TMF) that is visibly clear, highly reflective under sub-bandgap irradiation, and exhibits strong radiative cooling, thereby enhancing the performance of SCs. The proposed TMF exhibits 90.1% transmittance in the 0.38–1.1 μm range, 81.3% reflectivity the in 1.1–4.0 μm range, and an emissivity of 0.95 in the 6–20 μm range, enabling reduced temperatures and enhanced SC performance. Theoretical analysis and numerical modelling results demonstrate that, compared to glass encapsulation, the TMF reduces the SC operating temperature by 6.13 K and improves the relative photoelectric conversion efficiency by 2.40%, while maintaining stable performance across a wide range of incident angles of solar irradiation. Under practical weather conditions, the TMF reduces the bare-cell temperature by 15.22 K, accompanied by a 4.55% increase in power output. The current TMF provides a highly efficient spectral engineering-based thermal management strategy to enhance SC performance.