The optimal hybridization of photovoltaic (PV) and thermoelectric (TE) devices has long been considered ideal for the efficient harnessing solar energy. Our hybrid approach uses full spectrum solar energy via lossless coupling between PV and TE devices while collecting waste energy from thermalization and transmission losses from PV devices. Achieving lossless coupling makes the power output from the hybrid device equal to the sum of the maximum power outputs produced separately from individual PV and TE devices. TE devices need to have low internal resistances enough to convey photo-generated currents without sacrificing the PV fill factor. Concomitantly, a large number of p-n legs are preferred to drive a high Seebeck voltage in TE. Our simple method of attaching a TE device to a PV device has greatly improved the conversion efficiency and power output of the PV device (~30% at a 15°C temperature gradient across a TE device).

We describe n-type nanostructured bulk thermoelectric La-doped SrTiO₃ materials produced by spark plasma sintering of chemically synthesized colloidal nanocrystals. The La doping levels could be readily controlled from 3 to 9.0 at% by varying the experimental conditions. We found that nanoscale interfaces were preserved even after the sintering process, and the thermoelectric properties of the nanostructured bulk La-doped SrTiO₃ were characterized. An enhanced thermoelectric efficiency was observed and attributed to the large decrease in thermal conductivity obtained with no significant change in the Seebeck coefficient or electrical conductivity. The nanostructured bulk of the La-doped SrTiO₃ exhibited a maximum ZT of ∼0.37 at 973 K at 9.0 at% La doping, which is one of the highest values reported for doped SrTiO₃. Furthermore, the materials showed high thermal stability, which is important for practical high-temperature thermoelectric applications. This report demonstrates the high potential for low-cost thermoelectric energy production using highly stable and inexpensive oxide materials.

In this study, the effect of Ag or Sb addition on the thermoelectric properties of PbTe including the Seebeck coefficient, the electrical resistivity, and the thermal conductivity, was studied in the temperature range from 323 to 723 K. The major carriers in the Ag-doped and the Sb-doped PbTe are holes and electrons, respectively. A degenerate semiconductor behavior in the electrical transport properties was observed in the Ag-doped, whereas the semi-metallic in the Sb-doped. It was suggested from the results of the Hall effect measurement and the Seebeck coefficient that the effective mass was significantly altered by the Sb-doping. The maximum dimensionless figure of merit, $ZT$ , of ${\text{Pb}}_{1-\text{x}}{\text{Ag}}_{\text{x}}\text{Te}$ and ${\text{Pb}}_{1-\text{x}}{\text{Sb}}_{\text{x}}\text{Te}$ $\left(\text{x}=0.1\right)$ alloys showed 0.27 and 0.62 at 723 K, respectively. Based on the analysis of the Seebeck coefficient of the Ag or the Sb-doped PbTe, the interaction between Ag and Sb in PbTe, as expected in the ${\text{AgPb}}_{\text{m}}{\text{SbTe}}_{\text{m}+2}$ (LAST-m), may be supposed.