Hierarchical Bi–Te based flexible thin-film solar thermoelectric generator with light sensing feature

Thin-film solar thermoelectric generators show much promise in effective use of solar energy as a power supply for microscale devices. In this paper, we fabricated a flexible thin-film solar thermoelectric generator on the polyimide substrate using simple mask-assisted deposition process. The p-type Bi0.5Sb1.5Te3 and n-type Bi2Te2.7Se0.3 thermoelectric films with special hierarchical nanostructure were prepared, resulting in substantial improvement in the electrical conductivity. The solar thermoelectric generator with the hierarchical Bi–Te thin films is able to generate 220 mV of the output voltage and 80 μW of the maximum power for a temperature difference of 100 K. We also analyzed the optimized design for the solar thermoelectric generator. By employing a package for the thermoelectric legs and a perforated structure, the heat flow was restricted along the thermoelectric legs and a larger temperature difference was achieved. A fast electrical response to the on–off simulated solar light irradiation was also observed, indicating light sensing feature of the fabricated thin-film solar thermoelectric generator. Our results revealed that a remarkably enhanced output power has been achieved in the flexible thin-film solar thermoelectric generator due to the introduction of the improved thermoelectric films and the optimized thermal design.