Sunny alternatives

Perovskite crystal
Courtesy Rob Lavinsky, – published under CC-BY-SA-3.0
13 December 2017

The Australian Renewable Energy Agency is investing $29.2 million in 20 solar photovoltaic (PV) research projects, which together with further contributions from project partners will have a total value of around $102 million.

It is ARENA's third round of R&D funding to support early-stage solar PV projects, from flexible solar devices to semi-transparent, high-efficiency solar cells for integrating into windows.

While most of the projects focus on silicon technologies, the funding will also support new alternative materials, such as organic photovoltaics and perovskites, which would be lower cost to manufacture, printable or more sustainable.

Perovskite solar cells aim to increase the efficiency and lower the cost of solar energy.

The technology holds great promise, as perovskite PVs can efficiently convert a broad spectrum of wavelengths into electricity.

The material also offers flexibility, semi-transparency, and is light-weight. But a present overall costs of efficient perovskite solar cells are high, also because of gold often used in the electrodes, while cheaper cells tend to have short lifespan.

Another issue may be toxicity, as one of the breakdown products of perovskite is suspected to be carcinogenic, and many cells contain lead.

It includes two projects from researchers at the Australian National University, one of which is concerned with the development of so called tandem cells. This technology uses a layer of perovskite material on top of a silicon cell.

The advantage of this is that perovskite can convert the high-energy wavelengths in the blue spectrum of light much more efficiently into high-voltage electricity than silicon. Wavelengths in the red spectrum of light passing through are then converted to electricity by the underlying silicon layer.

But there is a catch: perovskite, while cheap to manufacture, is also quite unstable.

Professor Kylie Catchpole's team holds the world record for the most efficient perovskite tandem cell. And he is now working with Jinko Solar to develop a stable, mass-producible product by optimising large-scale manufacturing techniques.

A second funded ANU project is targeting new types of electrodes for perovskite solar cells. This could make an important contribution towards commercially viable perovskite cells as many metals react with the material.

Gold is at present used with the most efficient perovskite cells, but it is costly, and eventually also diffuses, rendering the cell unstable.

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