Effective thermoelectric performance in silicon by defect engineering

Silicon offers many advantages as a next generation thermoelectric material, meeting modern demands for earth abundance and non-toxicity while demonstrating compatibility with large scale manufacturing. Highly doped silicon has a thermoelectric power factor equal to current commercial materials; however the efficiency with which it can convert power and the effectiveness with which it can maintain the temperature gradients required for this conversion are negatively impacted by high thermal conductivity. Addressing this challenge typifies modern silicon thermoelectric research. Solutions have been found at the nanoscale, but nano-material dimensions introduce new challenges around translation to devices. In this work, large concentrations of vacancy defects are introduced to thin-film single crystalline silicon (c-Si) up to 2 μm thick for the first time and shown to reduce room temperature thermal conductivity by 97%. Effects have no nanodependence and material is visually indistinguishable from defect free bulk. Improvements in thermoelectric performance are investigated using ntype and p-type materials and comparative evaluation reveals an increase over benchmark bulk c-Si by a factor of 14. Best results return a value of z comparable with best results of SiGe. The first time for such a value in c-Si at these device-applicable material thicknesses.