Optimizing Thermoelectric Power Factor in p-Type Hydrogenated Nano-crystalline Silicon Thin Films by Varying Carrier Concentration

Most approaches to silicon-based thermoelectrics are focused on reducing the lattice thermal conductivity with minimal deterioration of the thermoelectric power factor. This study investigates the potential of p-type hydrogenated nano-crystalline silicon thin films (c-Si:H), produced by plasma-enhanced chemical vapor deposition, for thermoelectric applications. We adopt this heterogeneous material structure, known to have a very low thermal conductivity (similar to 1W/mK), in order to obtain an optimized power factor through controlled variation of carrier concentration drawing on stepwise annealing. This approach achieves a best thermoelectric power factor of similar to 3x10(-4)W/mK(2) at a carrier concentration of similar to 4.5x10(19)cm(3) derived from a significant increase of electrical conductivity similar to x8, alongside a less pronounced reduction of the Seebeck coefficient, while retaining a low thermal conductivity. These thin films have a good thermal and mechanical stability up to 500 degrees C with appropriate adhesion at the film/substrate interface.