Enhancing solar energy conversion by hybrid photovoltaic thermoelectric cells

Photovoltaic (PV) efficiency is intrinsically limited, since a relevant fraction of the available solar power is either transmitted (unconverted) or is partially degraded into heat by carrier relaxation in the PV absorber. However, the significant amount of heat made available thereof might be reused and partially converted into electricity by thermoelectric generators (TEGs), an opportunity made even more attractive by the increasing efficiency of thermoelectric (TE) materials. This talk will focus on the research aimed at developing hybrid photovoltaic−thermoelectric generators (HPVTEGs), namely tandem solar converters wherein a TE stage partially converts into electricity both the heat released by the PV stage and the sub-gap part of the solar spectrum. Strategies being developed to pair PV cells to TEGs will be discussed, addressing the role played by their thermal coupling and by the impact of heat dissipation on the efficiency of the HPVTEG. TEG layout in hybrid cells will be shown to require an ad hoc design critically depending on the PV material. The conclusion will be reached that HPVTEGs could enable the use of low-cost, non-critical PV materials, currently not considered for solar conversion technologies because of their marginal efficiency.