Upcycling Silicon Photovoltaic Waste into Thermoelectrics

Abstract Two decades after the rapid expansion of photovoltaics, the number of solar panels reaching end‐of‐life is increasing. While precious metals such as silver and copper are usually recycled, silicon, which makes up the bulk of a solar cells, goes to landfills. This is due to the defect‐ and impurity‐sensitive nature in most silicon‐based technologies, rendering it uneconomical to purify waste silicon. Thermoelectrics represents a rare class of material in which defects and impurities can be engineered to enhance the performance. This is because of the majority‐carrier nature, making it defect‐ and impurity‐tolerant. Here, the upcycling of silicon from photovoltaic (PV) waste into thermoelectrics is enabled. This is done by doping 1% Ge and 4% P, which results in a figure of merit ( zT ) of 0.45 at 873 K, the highest among silicon‐based thermoelectrics. The work represents an important piece of the puzzle in realizing a circular economy for photovoltaics and electronic waste.