Insect eyes inspire new solar cell design from Stanford

August 31, 2017

Packing tiny solar cells together, like micro-lenses in the compound eye of an insect, could pave the way to a new generation of advanced photovoltaics, say Stanford University scientists.

In a new study, the Stanford team used the insect-inspired design to protect a fragile photovoltaic material called perovskite from deteriorating when exposed to heat, moisture or mechanical stress. The results are published in the journal Energy & Environmental Science (E&ES).

"Perovskites are promising, low-cost materials that convert sunlight to electricity as efficiently as conventional solar cells made of silicon," said Reinhold Dauskardt, a professor of materials science and engineering and senior author of the study. "The problem is that perovskites are extremely unstable and mechanically fragile. They would barely survive the manufacturing process, let alone be durable long-term in the environment."

Most solar devices, like rooftop panels, use a flat, or planar, design. But that approach doesn't work well with perovskite solar cells.

"Perovskites are the most fragile materials ever tested in the history of our lab," said graduate student Nicholas Rolston, a co-lead author of the E&ES study. "This fragility is related to the brittle, salt-like crystal structure of perovskite, which has mechanical properties similar to table salt."

Eye of the fly

To address the durability challenge, the Stanford team turned to nature.

"We were inspired by the compound eye of the fly, which consists of hundreds of tiny segmented eyes," Dauskardt explained. "It has a beautiful honeycomb shape with built-in redundancy: If you lose one segment, hundreds of others will operate. Each segment is very fragile, but it's shielded by a scaffold wall around it."

Using the compound eye as a model, the researchers created a compound solar cell consisting of a vast honeycomb of perovskite microcells, each encapsulated in a hexagon-shaped scaffold just 0.02 inches (500 microns) wide.

"The scaffold is made of an inexpensive epoxy resin widely used in the microelectronics industry," Rolston said. "It's resilient to mechanical stresses and thus far more resistant to fracture."

Tests conducted during the study revealed that the scaffolding had little effect on the perovskite's ability to convert light into electricity.

"We got nearly the same power-conversion efficiencies out of each little perovskite cell that we would get from a planar solar cell," Dauskardt said. "So we achieved a huge increase in fracture resistance with no penalty for efficiency."

Durability

But could the new device withstand the kind of heat and humidity that conventional rooftop solar panels endure?

To find out, the researchers exposed encapsulated perovskite cells to temperatures of 185 degrees Fahrenheit (85 degrees Celsius) and 85 percent relative humidity for six weeks. Despite these extreme conditions, the cells continued to generate electricity at relatively high rates of efficiency.

Dauskardt and his colleagues have filed a provisional patent for the new technology. To improve efficiency, they are studying new ways to scatter light from the scaffold into the perovskite core of each cell.

"We are very excited about these results," he said. "It's a new way of thinking about designing solar cells. These scaffold cells also look really cool, so there are some interesting aesthetic possibilities for real-world applications."
-end-
The other co-lead authors of the E&ES study are Stanford postdoctoral scholars Brian Watson and Adam Printz.

Stanford University

Related Insect Articles from Brightsurf:

Solving global challenges using insect research
IRD researchers and their partners have published a special issue in the Current Opinion in Insect Science journal.

'Insect apocalypse' may not be happening in US
Scientists have been warning about an 'insect apocalypse' in recent years, noting sharp declines in specific areas -- particularly in Europe.

Global changes in insect populations reflect both decline and growth
The widely reported 'insect apocalypse' is far more nuanced than previous studies have suggested, according to a new study, which reports the findings of a meta-analysis featuring data from 166 long-term surveys across 1,676 sites worldwide.

Scientists' warning to humanity on insect extinctions
As the human race continues to battle the COVID-19 pandemic, scientists have found that the planet's insects are also facing a crisis after accelerating rates of extinction have led to a worldwide fall in insect numbers.

Insect decline more extensive than suspected
Compared to a decade ago, today the number of insect species on many areas has decreased by about one third.

Insect evolution: Insect evolution
Scientists at Ludwig-Maximilians-Universitaet (LMU) in Munich have shown that the incidence of midge and fly larvae in amber is far higher than previously thought.

Insect food webs
Biological diversity stabilizes species interactions.

Insect antibiotic provides new way to eliminate bacteria
An antibiotic called thanatin attacks the way the outer membrane of Gram-negative bacteria is built.

Taste is key in promoting insect-based food
Eating insects, instead of meat, could have significant environmental and health benefits.

Seeing pesticides spread through insect bodies
Osaka University-led team provides insights into the distribution of pesticides within insects using a newly developed method of insect sample preparation.

Read More: Insect News and Insect Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.