December 22, 2017

Flies shine light on path to cheaper solar energy

December 22, 2017

Curated by Hansong Xue

Scientists inspired by flies' eyes have come up with a hack to make solar cell materials easier to produce and more durable.

In 10 seconds? Can anyone see this? The geometry of a fly’s eye will be the key to push next-generation perovskite-based solar panels to the market, helping us reduce greenhouse gas emissions. (Read the science behind perovskite cells)


Pero…what? Perovskites – organic, inorganic or hybrid – are soft materials that share the same molecular structure as calcium titanium oxide. Some of them are ideal for solar cells, because they absorb light and produce electrical charge. (Read more about high-performance perovskite cells)

And what’s the rage about them? They are more sensitive than currently used silicone and can absorb light from the complete visible spectrum of light. Thanks to this, they can be used to create low-cost, highly efficient and lightweight solar cells for consumer use. In a short period of time their conversion efficiency jumped from 4% to over 20%… but there is one problem.

Oh no! What problem? Fear not – keep calm and carry on reading. Perovskite solar cells (PSCs) are instable and suffer irreversible degradation in high temperatures. They also crack easily. So, if you live in a sunny country – where you’d gain most from solar panels – they aren't much use... or weren't, until now. (Find out about their degradation here)

Oh, please, you sound like Dan Brown, just tell me the solution! All right. Stanford University researchers spotted the intricate structure of flies’ eyes – which contain thousands of ommatidia, or simple eyes. These are vulnerable, but are protected by a scaffold of hexagonal shapes. So, they applied the same structure to perovskites, and pronto, they got mechanically sturdy solar cells. Compartmentalising the cells improved their chemical stability too, making them last for up to six weeks in a hot and humid environment. (Read more here)

What else is being done to make these cells more stable? Scientists have taken to mathematical modelling of the four standard types of perovskite solar cells. This is done to analyse how much energy is lost, providing insights into improving cell device architecture and efficiency. They have also experimented by adding caesium or iodine ions into the solar cells, achieving 19% efficiency and lasting for 1,000 hours in direct sunlight. So, it sounds like the future of solar is bright!

What is solar cell efficiency?

Solar cell efficiency describes how much energy from sunlight can be converted by photovoltaic compounds in the cell into electricity. It is expressed in percentage.

The best solar cells in the world are capable of 40–50% efficiency, but these are too expensive for homeowners.

The average, respectable efficiency is currently around 20–24%, however Australian engineers managed to create cells that can harvest solar energy at a rate of 34.5%.

Psst, Hansong distilled 11 research papers to save you 582.8 minutes.

Curated by

Hansong Xue

Hansong is a PhD candidate, at the National University of Singapore, specialising in perovskite-based solar cells.

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