A team of scientists from Stanford University has discovered a method of constructing perovskite solar cells with enhanced durability by taking inspiration from the honeycomb structure of insect eyes. The cells, which use a crystalline material called perovskite, are cheaper and easier to produce than traditional silicon cells, and their efficiency has increased significantly since they were introduced in 2009.
One of the problems with the material is that the salt-like crystal structure of perovskite make it extremely fragile when compared to a conventional solar cell made with silicon. The vast majority of solar energy devices, including rooftop mounted panels, are flat in design. The inherent fragility and relative inability to cope with moisture and heat means that a traditional planar device made of perovskite solar cells would have a short shelf life.
To solve the problem, the team looked to nature, or, more specifically, to the eyes of insects. The eye of a fly is composed of thousands of individual photoreceptor units arranged hexagonally, and shielded by a kind of scaffold.
The team from Stanford University decided to follow this model, and constructed a honeycomb of compound perovskite microcells protected by hexagon-shaped scaffold 0.02 inches (500 microns) wide, constructed from a cheap, readily available epoxy resin. The cells are connected by electrodes on the back and front of the cells.
"We got nearly the same power-conversion efficiencies out of each little perovskite cell that we would get from a planar solar cell," said professor of materials science and engineering at Stanford University, and senior author of the study, Reinhold Dauskardt. "So we achieved a huge increase in fracture resistance with no penalty for efficiency."
It was found that the scaffold made the cells far more resistant to fracturing, and had little effect on the efficiency of the cells converting light to electricity.
The team also tested the honeycomb solar cell's ability to withstand extreme conditions by exposing it to temperatures of 185 ºF (85 ºC) and 85 percent humidity for a period of six weeks.
The new design stood up to the pressure, allowing the cells to survive, and to continue to generate electricity with a relatively high rate of efficiency. Looking forward, the team members plan to further enhance their design by researching ways to scatter light into the core of the microcells – a measure they believe will improve the efficiency of the technique.
A paper on the research has been published in the journal Energy & Environmental Science.
Source: Stanford University
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