Stanford Researchers Draw Inspiration from Insect Eyes to Create New Solar Cell

Scientists will now be able to resolve a major hurdle using a new solar cell inspired by the compound eyes of insects to create solar panels based on a promising material called perovskite.

Stanford University Researchers sat packing minute solar cells together, like micro-lenses in the compound eye of an insect, which could pave the way for a new generation of advanced photovoltaics.

In a recent research, these Researchers used the insect-inspired design to protect a delicate photovoltaic material called perovskite from being affected when exposed to moisture, heat or mechanical stress. The results are published in the Energy & Environmental Science (E&ES) journal.

Perovskites are promising, low-cost materials that convert sunlight to electricity as efficiently as conventional solar cells made of silicon. 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.

Reinhold Dauskardt, Senior Author of the study and a Professor of Materials Science and Engineering

A majority of solar devices, like rooftop panels, use a flat or planar design. But that method does not function well with perovskite solar cells.

Perovskites are the most fragile materials ever tested in the history of our lab. This fragility is related to the brittle, salt-like crystal structure of perovskite, which has mechanical properties similar to table salt.

Nicholas Rolston, Graduate Student and Co-lead Author of the E&ES study

Eye of the fly

To solve the durability challenge, the Stanford team looked at nature for answers.

“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 team developed a compound solar cell made up of a huge honeycomb of perovskite microcells, each encapsulated in a hexagon-shaped scaffold measuring just 0.02” (500 μm) in width.

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

Nicholas Rolston, Graduate Student and Co-lead Author of the E&ES study

Tests conducted during the research showed that the scaffolding had minimal effect on how efficiently perovskite changed 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 novel device tolerate the kind of humidity and heat that conventional rooftop solar panels withstand?

To test it, the encapsulated perovskite cells were exposed to temperatures of 185 °F (85 °C) and 85% relative humidity for six weeks. In spite of these extreme conditions, the cells continued to produce electricity at comparatively high rates of efficiency.

Dauskardt and his colleagues have filed a provisional patent for this technology. To enhance efficiency, they are exploring new ways to disperse 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.”

The other Co-lead Authors of the research are Stanford Postdoctoral Scholars Brian Watson and Adam Printz.

This study was supported by a grant from the Stanford Precourt Institute for Energy with further support from the National Science Foundation.