Efficiency enhancement of a-Si and CZTS solar cells using different thermoelectric hybridization strategies

The performances of two hybrid thermoelectric photovoltaic systems are compared. In the first instance, a photovoltaic (PV) device and a thermoelectric generator (TEG) are optically coupled using a vacuum-sealed compound parabolic concentrator (CPC). As an alternative, PV and TEG devices are thermally coupled putting them directly in contact to each other. Single-junction a-Si and heterojunction Cu2ZnSnS4 (CZTS) have been considered as PV systems. The two systems are studied by varying the heat transfer coefficient of the cooling system between the TEG cold side and the ambient, the TEG device fill factor, and the optical concentration. Hybridization, in both configurations, always enhances the efficiencies, up to ≈ 57% for single-junction a-Si and up to ≈ 35% for the heterojunction CZTS. It will be shown that while direct thermal contact enables larger efficiencies, optical coupling grants lower temperatures at the PV side, enhancing reliability and lifetime. Further advantages and limitations of both configurations will be discussed.