Fool’s Gold in Solar Cells

Scientists at the University of California at Berkeley are developing new solar cells based on pyrite, otherwise known as fool’s gold. Fool’s gold is four or five times more plentiful than the silicon most commonly used in solar cells and should be an excellent material for photovoltaics – in theory, it absorbs more wavelengths of light using less material than silicon – but that promise has not previously been realized in practical use.
An iron pyrite (fool's gold) sample from Elba, Italy. (Source: Hannes Grobe)
An iron pyrite (fool’s gold) sample from Elba, Italy. (Source: Hannes Grobe)

Pyrite has been explored as a source of photovoltaic material for years, but has only turned about 3% of the light that strikes it into electrical power. Silicon, gallium arsenides, and other materials used in current commercial cells achieve many times that level of efficiency. Theoretically it should also be more efficient at converting light to power, but slight variations in the physical structure or phase of the mineral significantly degrade that efficiency.

Professor Cyrus Wadia and his team of researchers at Berkeley are overcoming this problem by integrating nanocrystals into the pyrite at the atomic level. These crystals should regulate the consistency of the mineral structure and reduce power lost from phase differences. The crystals also increase the number of wavelengths the mineral can capture, another key factor in increasing efficiency.

Wadia’s research is still in the early stages. He currently has two pyrite-based cells which only achieve an efficiency of 1.6%, about half of the earlier failed attempts to use fool’s gold for photovoltaics. Wadia’s current cells incorporate cadmium in addition to the pyrite, a material he hopes to remove in later iterations of the design.

Others are also researching the use of pyrite-based solar cells. NLV Solar and Swedish car designer Koenigsegg incorporated pyrite-based solar cells into their Quant concept car. They claim their version of the photovoltaic cell converts 50% of sunlight striking it into usable electricity. The car is experimental and likely will never be sold commercially. It is unknown whether its solar cells are appropriate or available for other uses.

TFOT has previously reported on other solar cells and photovoltaic technology, including glitter-sized photovoltaic cells, an organic solar concentrator capable of replacing windows or skylights, rollable solar panels that could be used with portable electronics or on irregularly shaped surfaces, and solar cells manufactured from plant material instead of plastics.

Read more about Cyrus Wadia and his research at his website or at his profile page at the Energy Institute at Berkeley’s Haas School of Business.