Scientists are researching a new crystal, that could lead to cheaper solar power than currently offered by silicon.

Research is being carried out into the qualities of perovskite cells, with the FT reporting that it could reduce costs to pennies per watt.

Certain perovskites have been shown to be particularly adept at absorbing light, with a power conversion efficiency of 22 per cent, outperforming all other alternative materials being researched at the present time.
Since first being tested a decade ago, scientists have been enthused by the rapid rate of progress, but on the downside, there is still work to be done on overall viability.

The crystals dissolve easily, and so far are unable to handle humid conditions and must be protected from moisture with sealed glass plates. Also, while scientists have achieved high efficiency with very small perovskite cells, they have not been able to replicate the effect with larger cell areas.

“The perovskites are certainly not as stable as silicon,” says Michael McGehee, professor of materials science at Stanford University told the FT. “So that’s the main challenge. The other is just that it is so new — it hasn’t been scaled yet, and factories haven’t been built. It will take some time.” No company manufactures commercial perovskite solar cells at large scale yet, although one, Oxford PV, an offshoot of Oxford university, has a pilot production facility for perovskite solar cells in Germany.

The academics and small companies researching perovskites will, for the time being, struggle to match the high levels of funding going into silicon research. “It is hard right now to go head to head with silicon and beat it,” says Prof McGehee. “The reason is that they already have massive economies of scale.” In the near term, one solution advocated by Prof McGehee is the use of “tandem” solar cells, which layer a perovskite on top of traditional silicon.

The perovskite cell, which is semi-transparent, captures certain wavelengths in the visible spectrum of light, allowing other wavelengths to pass through and be captured by the silicon cell underneath. Prof McGehee’s research has shown that a tandem cells are 10 per cent more efficient than silicon cells alone. It could be a way for the new material to break into the silicon-dominated market. A solar cell on which the crystalline material perovskite is applied

“If you go on top of silicon, you are essentially upgrading something that is a $30bn per year market and offering silicon companies something that can improve [their output],” he explains. If the hurdles of scale and stability can be overcome, perovskite solar cells have the potential to change the economics of solar power, as they are much cheaper to produce than silicon cells. Perovskite crystals can be produced at relatively low temperatures, unlike silicon which requires a tremendous amount of heat to make a wafer.

Last year more than 90 GW of solar power were installed globally, and there is now a drive to research new materials and produce the energy even more cheaply.