Photovoltaic-thermoelectric hybrid systems: Structural design, thermal management, control optimization and application expansion

Photovoltaic-thermoelectric generator (PV-TEG) hybrid systems have been widely investigated for cascade solar energy utilization, yet their practical advantages depend on the coupled balance among PV cooling, thermoelectric temperature-gradient formation, optical allocation and system-level losses. This review critically summarizes recent progress in PV-TEG systems, covering structural design, thermal and optical management, operational control, multi-objective optimization and application expansion. Recent studies show that advanced cooling and heat-transfer structures can reduce PV temperature by several to more than 20°C, but the net electrical gain remains strongly constrained by thermoelectric temperature difference, interfacial thermal resistance, parasitic pumping power and optical losses. Control strategies have evolved from conventional perturb-and-observe and incremental-conductance algorithms to hybrid, intelligent and data-driven maximum power point tracking methods, although outdoor implementation still requires improved sensing, embedded computation and validation under dynamic irradiance and temperature conditions. Application opportunities in building integration, green hydrogen production, wearable electronics and autonomous devices are further discussed, together with advances in thermoelectric materials and interfacial manufacturing. Key challenges include limited thermoelectric efficiency under low-grade heat, inconsistent performance metrics, uncertain cost-performance trade-offs and insufficient long-term reliability data. Finally, recommended evaluation metrics are proposed to support reproducible comparison, net-gain assessment and engineering translation of PV-TEG systems.