Perovskite crystals are one of the most promising new solar photovoltaic technologies, they’ve already proved highly efficient at converting sunlight into electricity and promise to be cheap to produce. But researchers are trying to figure out how to best make these into durable, long-lasting solar panels and devices. Stanford researchers think they may have found an answer in an unlikely place—fly eyes.
"Perovskites are promising, low-cost materials that convert sunlight to electricity as efficiently as conventional solar cells made of silicon," explained Reinhold Dauskardt, senior author of the research, which appeared in the journal Energy & Environmental Science (E&ES). Dauskardt is a professor of materials science and engineering at Stanford. "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."
Dauskardt and fellow authors Nicholas Rolston, Brian Watson and Adam Printz created a tiny hexagonal scaffold made from an epoxy resin that’s cheap and used in microelectronics to encapsulate perovskite solar cells. They’ve already applied for a provisional patent for the new technology and are now investigating ways to reflect or scatter more light from the epoxy into the solar cell.
"Perovskites are the most fragile materials ever tested in the history of our lab," said Rolston, co-lead author of research. "This fragility is related to the brittle, salt-like crystal structure of perovskite, which has mechanical properties similar to table salt."
To counteract that fragility, the researchers made miniature solar solar cells. "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.”
The hexagonal epoxy structure allows the microcells, which are 500 microns wide, to operate and conduct electricity even if neighboring microcells are damaged. Rolston added, ”It's resilient to mechanical stresses and thus far more resistant to fracture."
"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.”
The researchers also conducted various stress tests on the cells. The tests included keeping the cells exposed to temperatures of 185 degrees Fahrenheit and 85 percent relative humidity for six weeks. They maintained high rates of efficiency throughout the testing.Tweet