Boosting Total Conversion Efficiency of Hybrid Photovoltaic–Thermal via a Spectral Splitter/Absorber Based on Lossy Periodic Structured Media

A spectral splitter plays a crucial role in the hybrid photovoltaic (PV)–thermal design for efficient solar energy harvesting. Herein, the lossy medium periodic structure of ITO/Si is utilized to construct a novel spectral splitter/absorber that selectively reflects the solar energy in PV band while absorbing the rest of solar energy. The as-prepared spectral splitter/absorber demonstrates a weighted reflectance of 75.6% in the PV band, an absorptance of 83.1% in the photothermal (PT) band, as well as superior angular performance across a broad incident range of 0°–60°. The proposed hybrid photovoltaic–thermal (PVT) system assembled with the spectral splitter/absorber with 1100 nm long edge of the PV band enhances the total electrical efficiency to 26.5%, higher than that of the individual Si PV cell (19.1%), resulting from the precise modulation of solar spectrum via the splitter/absorber to realize efficient utilization of solar energy in different bands. The temperature of PV cells in a hybrid PVT system also declines by ≈25 °C compared with the single-Si PV cell. The PV band can be easily shifted to match other narrow-bandgap PV cells due to intrinsic properties of near-zero k of both ITO and Si at near-infrared wavelength range and the large difference in n between them.