Fishnet metastructure for IR band trapping for enhancement of photovoltaic–thermoelectric hybrid systems

• Embedding a fishnet metastructure in a photovoltaic–thermoelectric hybrid system is proposed.
• The geometry and material properties of the fishnet metastructure are the most critical parameters.
• Pitch, width and thickness of the fishnet metastructure should be optimized.
• Solar thermal absorption in the near infrared spectrum is increased.
• The electromagnetic response of the system is simulated with one unit cell by assuming infinite periodic extensions.

We propose embedment of a fishnet metastructure for a photovoltaic–thermoelectric (PV–TE) hybrid system to produce more electrical power of a thermoelectric generator by absorbing more solar thermal energy. The hybrid system consists of a hydrogenated amorphous silicon (a-Si:H) thin film solar cell as a top cell and a thermoelectric generator as a bottom cell. A planar fishnet structure is embedded in a back passivation layer of the solar cell to enhance solar thermal absorption near the infrared band of the solar spectrum. The absorbed thermal energy by the fishnet embedded solar cell is transferred to the TE generator, which increases temperature difference between hot and cold sides of the TE generator that enables to produce more electric power. The fishnet structure is optimized through the parametric simulation in terms of pitch, width and thickness. To calculate the total solar thermal energy of the hybrid system, the solar power spectrum is modeled by using the power spectral density of blackbody radiation. The total absorbed solar energy over infrared band is calculated by windowing absorption of the hybrid system to the modeled power spectral intensity. The hybrid system with the optimized fishnet structure absorbs more solar thermal energy than the system without fishnet by around 12 folds. This study would provide some enlightenment for the high performance of PV–TE hybrid systems.

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