A new design of perfect infrared absorber featuring optical transparency for enhanced performance in transparent solar cells

Abstract Transparent and semi-transparent photovoltaics enable seamless integration of solar panels into building elements, thereby advancing the adoption of renewable energy utilization in the built environment without compromising design or functionality. Metamaterials can absorb a broad spectrum of light in the mid-infrared range while remaining transparent in the visible spectrum (400–800 nm). This paper introduces a novel optically transparent perfect absorber (OTPA) utilizing an indium tin oxide (ITO) substrate as its foundation. The dual functionality of ITO, exhibiting strong absorption in the infrared while remaining transparent in the visible range, makes it an ideal candidate for integration into transparent solar cells (TSCs). The proposed metamaterial-based solar absorber comprises four identical square patches separated from the ITO ground plane by a Zinc Sulphide (ZnS) dielectric layer. The proposed structure employs geometrically optimized square patches to achieve broadband absorption, where nanoscale design modifications play a critical role in enhancing impedance matching and tuning resonant modes for maximum efficiency. The proposed ZnS/ITO-based Solar thermophotovoltaic (STPV) design achieves over 98% absorption in the mid-infrared spectrum (3000–14000 nm) while maintaining an average optical transmittance above 70% with a peak transmittance of 87% in the visible spectrum. Simulation results confirm broadband absorption under both transverse electric (TE) and transverse magnetic (TM) polarizations, maintaining high performance for incident angles up to 70° and polarization angles up to 90°. Infrared absorption efficiency, evaluated using the Fabry–Perot model, reveals a strong agreement with simulation results. The proposed ultrathin transparent absorber is of great potential for applications in building integrated photovoltaics (BIPV), radiative cooling and infrared imaging.