Thin-Film Thermoelectric Modules for Power Generation Using Focused Solar Light

We demonstrated the fabrication of thin-film thermoelectric generators and evaluated their generation properties using solar light as a thermal source. Thin-film elements of Bi 0.5 Sb 1.5 Te 3 ( p -type) and Bi 2 Te 2.7 Se 0.3 ( n -type), which were patterned using the lift-off technique, were deposited on glass substrates using radiofrequency magnetron sputtering. After annealing at 300°C, the average Seebeck coefficients of p - and n -type films were 150 μ V/K and −104 μ V/K, respectively, at 50°C to 75°C. A cylindrical lens was used to focus solar light to a line shape onto the hot side of the thin-film thermoelectric module with 15 p – n junctions. The minimum width of line-shaped solar light was 0.8 mm with solar concentration of 12.5 suns. We studied the properties of thermoelectric modules with different-sized p – n junctions on the hot side, and obtained maximum open voltage and power values of 140 mV and 0.7 μ W, respectively, for a module with 0.5-mm p – n junctions. The conversion efficiency was 8.75 × 10 −4 %, which was approximately equal to the value estimated by the finite-element method.