Hybrid thermoelectric-photovoltaic (TE-PV) systems represent a promising approach to enhance energy harvesting by synergistically combining the complementary mechanisms of photovoltaic conversion and thermoelectric power generation. These systems aim to maximize the utilization of the solar spectrum while recovering waste heat from PV cells, thereby improving overall efficiency beyond the limits of standalone technologies. Key design strategies include tandem architectures, spectral splitting, and advanced thermal management, each contributing to performance optimization under varying operational conditions.

Tandem architectures integrate thermoelectric modules directly with photovoltaic cells to form a unified energy conversion system. In such configurations, the PV component absorbs high-energy photons to generate electron-hole pairs, while the TE module converts the residual thermal energy from the PV cell into additional electrical power via the Seebeck effect. A critical consideration in tandem designs is the thermal coupling between the PV and TE layers. Excessive heat can degrade PV performance, necessitating precise control over the temperature gradient across the TE module. Studies have demonstrated that optimal performance is achieved when the PV cell operates at elevated but stable temperatures, typically between 50°C and 100°C, allowing the TE module to maintain a sufficient ΔT for efficient power generation. For instance, a hybrid system using a silicon PV cell coupled with bismuth telluride TE modules achieved a combined efficiency of 15.2%, surpassing the standalone PV efficiency by approximately 2.3%.

Spectral splitting is another strategy employed in hybrid TE-PV systems to enhance energy harvesting. Unlike tandem designs, spectral splitters separate incoming sunlight into distinct wavelength bands, directing high-energy photons to the PV cell and lower-energy photons to a thermal absorber that drives the TE module. This approach minimizes thermalization losses in the PV cell while maximizing the utilization of infrared radiation for thermoelectric conversion. Dichroic mirrors, luminescent solar concentrators, and nanoparticle-based filters have been explored as spectral splitting mechanisms. Experimental setups using gallium arsenide PV cells with selective filters and skutterudite TE materials have reported system efficiencies exceeding 18%, leveraging the reduced thermal load on the PV component. The spectral splitting method is particularly advantageous in concentrated solar environments, where high photon flux can be precisely partitioned to optimize both conversion pathways.

Thermal management is a decisive factor in the performance and longevity of hybrid TE-PV systems. Effective heat dissipation from the PV cell is essential to prevent efficiency drops due to rising temperatures, while maintaining a controlled temperature gradient across the TE module is critical for sustained power output. Passive cooling techniques, such as heat sinks and radiative coolers, are often employed, but active cooling methods like microfluidic channels or thermosiphons may be necessary for high-power applications. Research on hybrid systems with integrated heat pipes demonstrated a 20% improvement in TE output compared to uncooled configurations, highlighting the importance of thermal regulation. Additionally, phase-change materials have been investigated for transient thermal buffering, stabilizing system performance under fluctuating solar irradiance.

The theoretical efficiency limits of hybrid TE-PV systems are influenced by the bandgap of the PV material, the thermoelectric figure of merit (ZT) of the TE module, and the spectral utilization efficiency. Under standard AM1.5 solar spectrum conditions, the maximum theoretical efficiency for an idealized tandem system with a single-junction PV cell and an optimized TE module approaches 35%, assuming a PV bandgap of 1.1 eV and TE ZT values above 2.0. However, practical systems face challenges such as optical losses, contact resistances, and parasitic heat conduction, which constrain real-world efficiencies to lower values. Recent modeling studies suggest that hybrid systems using multijunction PV cells and segmented TE materials could achieve efficiencies nearing 25% under non-concentrated sunlight, provided that spectral and thermal losses are minimized.

Field demonstrations of hybrid TE-PV systems have validated their potential in real-world conditions. A pilot installation in a sunbelt region utilized crystalline silicon PV cells paired with bismuth-antimony TE modules, achieving an annual average efficiency of 14.7% with a peak output of 18.2% during high-irradiance periods. Another project integrated cadmium telluride PV modules with skutterudite-based TE generators, demonstrating a 12% increase in energy yield compared to standalone PV arrays over a six-month operational period. These deployments underscore the importance of system-level optimization, including alignment with local solar profiles and adaptive thermal management strategies.

Challenges remain in scaling hybrid TE-PV systems for widespread adoption. Material compatibility issues, such as thermal expansion mismatches between PV and TE components, can lead to mechanical degradation over time. The cost-effectiveness of hybrid systems also requires further improvement, as high-performance TE materials like bismuth telluride and skutterudite remain expensive compared to conventional PV materials. Research into low-cost, earth-abundant TE materials, such as magnesium silicides and copper-based chalcogenides, could address this barrier. Additionally, standardization of hybrid system metrics and testing protocols is needed to facilitate fair comparisons with standalone technologies.

Future advancements in hybrid TE-PV systems are likely to focus on nanostructured materials and adaptive designs. Nanocomposite TE materials with reduced thermal conductivity and enhanced power factors could improve ZT values, while spectrally selective PV coatings might further minimize thermalization losses. Dynamic systems capable of reconfiguring their optical or thermal pathways in response to environmental conditions could also enhance robustness across diverse climates. The integration of hybrid systems with energy storage solutions, such as thermal batteries or supercapacitors, may further optimize energy delivery for off-grid applications.

In summary, hybrid thermoelectric-photovoltaic systems offer a viable pathway to higher solar energy conversion efficiencies by harnessing both electrical and thermal energy from sunlight. Tandem architectures, spectral splitting, and advanced thermal management techniques each contribute to performance gains, with field demonstrations confirming their practical feasibility. While challenges in cost, durability, and standardization persist, ongoing research into materials and system design continues to push the boundaries of what hybrid energy harvesting can achieve. The convergence of these technologies holds particular promise for applications requiring compact, high-efficiency power generation, such as remote sensors, aerospace systems, and distributed energy grids.