Biomimetic omnidirectional broadband structured surface for photon management in photovoltaic-thermoelectric hybrid systems

An advanced photon management approach is developed for a photovoltaic-thermoelectric hybrid system to increase the solar energy utilization efficiency. A biomimetic parabolic-shaped structure on the Si film and a thin SiO₂ film at the bottom of the Si film as back-antireflection coating improves the absorptance of photons with wavelengths of 0.3-1.1 μm, which can generate electron-hole pairs. Photons with wavelengths of 1.1-2.5 μm transmit through the structured surface and are absorbed by the thermoelectric modules, which improves the conversion efficiency of the entire hybrid system. The structured surface with graded refractive index can effectively harvest photons with wavelengths of 0.3-2.5 μm. The effects of the structural parameters and the incident angle on the spectral features of the structured surface are analyzed. The results indicate that the structured surface provides high omnidirectional absorptance for wavelengths of 0.3-1.1 μm and high transmittance for wavelengths of 1.1-2.5 μm as well as favorable polarization-insensitive features over a good incident angle range as a good candidate for the photovoltaic-thermoelectric hybrid systems.