Researchers are working to uncover the secrets of crystalline materials called hybrid perovskites in hopes of achieving cheap, super-efficient solar power.
In only five years of development, hybrid perovskite solar cells showed the same power conversion efficiencies that took decades to achieve with other types of top-performing materials, the University of Utah reported. In the past scientists have had an unclear idea of what occurred in the hybrid perovskite solar cells on a molecular level, this new study could help answer some of the puzzling questions. The recent study also demonstrated a rapid testing method that uses magnetic fields to determine the performance of different prototypes of hybrid perovskite materials.
A team of researchers applied magnetic fields to the material to look at how it influence the behavior of electrons and "holes" in semiconductor compounds. Contrary to previous belief, the researchers discovered there were significant magnetic field effects, and the magnetic properties of heavy atoms of lead and iodine were observed to minimize these effects in hybrid perovskite solar cells.
The researchers identified a mechanism, dubbed delta-g, that could help explain how a magnetic field influences the spin configuration of electron-hole pairs. The spin configuration changes the rate at which electron-hole pairs split apart or recombine, which has an effect on the electrical conductivity and photoluminescence of the perovskite. The scientists were able to measure delta-g directly using a technique called field-induced circular polarized emission, they also used a spectroscopy technique to observe the lifetimes of electron-hole pairs created by light absorption in the hybrid perovskite solar cells. All of these measurements proved to line up with the idea of delta-g.
The research helped answer the question of whether hybrid perovskite devices behaved more like silicon solar cells or were closer to xcitonic solar cells made of organic polymers.
"This material is not excitonic. If it were, we would not see this effect. It is not like organic photovoltaic materials," said senior author Z. Valy Vardeny, a distinguished professor of physics at the University of Utah.
The perovskite photovoltaic devices can convert sunlight into electrical power with an efficiency of almost 20 percent; this is not as impressive as the 26 percent achieved by the best silicon cells, but perovskite photovoltaic devices can be manufactured at a fraction of the cost. The researchers believe harnessing solar energy through photovoltaic cells has become easier with the development of hybrid perovskite.
"This is important since the gasoline price at the pumps would not stay that low forever," Vardeny concluded.
The findings were published in a recent edition of the journal Nature Physics.