Are perovskite PVs the new blue sky thinking on solar panels?

The simple answer to that is maybe, but there are a few buts clouding the perovskite horizon. However, there is no doubt about the excitement perovskite photovoltaics (PV) is causing within the solar power industry.

It shows very promising performance with some tests producing efficiency levels in the region of 30%, although levels of 22% are more regularly achieved and could therefore be considered as more realistic. Nevertheless, even 22% is impressive compared to the usual average of 15% for existing PV technology.

But lurking behind that promise of impressive efficiency levels lies some good, bad and potentially nasty operational characteristics so ultimately the question is do the positives outweigh the negatives?

But before delving into those characteristics what is a perovskite solar cell? Fundamentally it is a type of solar cell which includes a perovskite compound which typically is a lead or tin halide-based material working as the light-harvesting layer within a solar cell.

Cheap to produce

Perovskite materials such as the methylammonium or formamidinium lead halides are cheap to produce and simple to manufacture and, in addition to these advantages, perovskite is very simple to process. Traditional silicon cells need costly multistep processes involving very high temperatures and vacuums in clean room facilities to produce flawless silicon wafers. In comparison perovskite material can be manufactured with uncomplicated wet chemistry and processing techniques in a conventional lab environment So processing perovskite is easier and it can be made into lightweight, thin, flexible and possibly stretchable cells. Unsurprisingly, electronics designers and researchers are certain that those characteristics will open up many more applications for solar cells.

But perovskite does have its disadvantages. It can struggle under certain ambient and climatic conditions. A major concern is it decomposes in the presence of water and substantial encapsulation to protect perovskite from moisture can add to the cell cost and weight. Water vapour penetrating the perovskite can produce reactive iodides that quickly corrode the metal electrodes. However, progress is being made to resolve this fundamental problem and stable cells that are resistant to moisture have been developed and these are achieving efficiencies of 16%.

Toxicity concerns

But one of the major negatives relating to perovskite concerns a substance called PbI which is one of the breakdown products of perovskite. This is known to be toxic and there are concerns that it may be carcinogenic although in fairness there is still considerable debate on this yet unproven point.

However, these factors do suggest that additional cost and weight would have to be added to the design of solar cells using perovskite by designing in a glass panel to fully seal the product. Although considered to be heavier, glass would be preferable to plastic because it is considered more durable and also because plastic is susceptible to piercing.

Manufacturers of solar panels would do well to heed this warning on toxicity relative to perovskite. The industry has already had to address many disconcerting environmental issues that partially deplete the environmental good that solar cells can offer.

There are different types of PV technology that use different manufacturing processes that involve caustic substances like sodium hydroxide and hydrofluoric acid. And crystalline PV cell silicon is made using silane gas, the production of which results in waste silicon tetrachloride which is toxic.

So yes perovskite does have real potential but only when some of the practical problems involving its use have been genuinely resolved.