‘Two decades after the rapid expansion of photovoltaics (PVs), the number of solar panels reaching end-of-life is increasing,’ observes the National University of Singapore. Its claims it has found a way to transform discarded solar cells into ‘thermo-electronics’.
While precious metals such as silver and copper are typically recycled from used solar panels, silicon, which makes up the bulk of a solar cell, goes to landfill. The impurities of most silicon-based technologies mean it is uneconomic to purify waste silicon.
Thermo-electrics could be a game-changer, according to Ady Suwadi, assistant professor in the department of materials science and engineering. His team has been conducting tests on the PV module material for the past two years have found that polycrystalline silicon can be pulverised into powder and pelletised into ingots.
The novel process uses spark plasma sintering to dope the silicon with 1% germanium and 4% phosphorus. Suwadi’s team processed 16 cm fragment at 1 150° Celsius for five minutes.
The upcycling of silicon, present in about 90% of decommissioned PV modules, from PV waste into thermos-electrics is said to be possible for all types of silicon-based panels.
Suwadi explains that thermo-electric material has a dual function: converting waste heat into electricity and electricity into cooling. The researcher further points out that thermo-electronics represent 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.’
Suwadi is confident the innovative work represents ‘an important piece of the puzzle’ in realising a circular economy for PV and electronic waste.
The research, which was published in the journal Advanced Materials, was named as one of the university’s ten best Youth Sustainable Projects of 2022.