Oxford and lead free Perovskite solar cells

Solar cells made from ‘perovskite’ materials have been causing a storm – reaching 17% efficiency from a standing start only a few years ago. They are made by deposition, and can be made over large areas without the cost of wafer processing.

Pb-free perovskite solar Credit: Oxford University

A team led by researchers at the University of Oxford has demonstrated that the Pb in solar cells based on Pb halide perovskites can be replaced with tin.

Although the amount of lead in each cell is tiny, the presence of a toxic metal could still be a barrier to commercialisation.

“We wanted to try and replace the lead with something similar but non-toxic. Tin has been reported in perovskites before, but not in a solar cell, so we decided to see if it would work,” said Oxford physicist Nakita Noel. “We found that by using tin we managed to keep everything that is good about lead in a solar cell but use a metal that is safe, cheap, and abundant.”

The prototype achieved 6% efficiency, with 20% theoretically possible.

Now tin has replaced Pb, other metals could be found to work in the perovskite structure.

One large disadvantage is that the tin perovskite degrades in the presence of oxygen and moisture. The researchers are confident that further work will enable them to create cells that are stable and can operate in air for long periods of time.

The work is to be published in the journal Energy & Environmental Science in a paper ‘Lead-free organic-inorganic tin halide perovskites for photovoltaic applications’.

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