Power/Performance Bits: Aug. 19

Scientists at the University of Sheffield have pioneered spray-on solar cells using perovskite; MIT researchers propose diverting a dangerous waste stream at the same time producing low-cost photovoltaics.

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Spray-on power
In a discovery that could help cut the cost of solar electricity, a team of scientists at the University of Sheffield has fabricated perovskite solar cells using a spray-painting process.

The researchers had used the spray-painting method previously to produce solar cells using organic semiconductors – but using perovskite is a major step forward, they asserted.

Efficient organometal halide perovskite based photovoltaics were first demonstrated in 2012 and are now a promising new material for solar cells as they combine high efficiency with low materials costs.

This class of material offers the potential to combine the high performance of mature solar cell technologies with the low embedded energy costs of production of organic photovoltaics, the researchers explained.

The best certified efficiencies from organic solar cells are around 10%, where perovskite cells now have efficiencies of up to 19%, which is not so far behind that of silicon at 25% – the material that dominates the world-wide solar market.

From old batteries to solar cells
A system proposed by MIT researchers recycles materials from discarded car batteries, which are a potential source of lead pollution, into new, long-lasting solar panels that provide emissions-free power.

The system is based on a recent development in solar cells that makes use of a compound called perovskite — specifically, organolead halide perovskite — a technology that has rapidly progressed from initial experiments to a point where its efficiency is nearly competitive with that of other types of solar cells.
This material went from initial demonstrations to good efficiency in less than two years, and already, perovskite-based photovoltaic cells have achieved power-conversion efficiency of more than 19%, which is close to that of many commercial silicon-based solar cells.

Initial descriptions of the perovskite technology identified its use of lead, whose production from raw ores can produce toxic residues, as a drawback. But by using recycled lead from old car batteries, the manufacturing process can instead be used to divert toxic material from landfills and reuse it in photovoltaic panels that could go on producing power for decades, the researchers said.

And because the perovskite photovoltaic material takes the form of a thin film just half a micrometer thick, the MIT teams’ analysis showed that the lead from a single car battery could produce enough solar panels to provide power for 30 households.