A group of scientists from the University of Virginia is seeking to improve the lack of stability in the crystal structure of hybrid organic-inorganic perovskites (HOIPs), in order to extend the durability of their performance; an achievement that may be particularly interesting for the development of more efficient solar cells.
In a paper published on the scientific journal Proceedings of the National Academies of Sciences, the research team claims that it has found a new way to better manipulate HOIPS for greater efficiency, as well as for longer-lasting efficiency under changing conditions.
According to the scientists, the key for extending the electron lifetimes would be the rotation of the molecules in the HOIPs, which would allow charged electrons not to dissipate and to better endure, thus resulting in the higher energy-conversion efficiency of these materials.
The researchers used microscopic detection devices and measurement techniques with high-performance computer modeling to observe the mutating molecular structures of the materials.
“Our results,” the UVA scientists said, “reveal that the band-edge carrier lifetime increases when the system enters from a phase with lower rotational entropy to another phase with higher entropy. These results imply that the recombination of the photoexcited electrons and holes is suppressed by the screening, leading to the formation of polarons and thereby extending the lifetime. Thus, searching for organic–inorganic perovskites with high rotational entropy over a wide range of temperatures may be key to achieving superior solar cell performance.”
According to the research team, the current record efficiency of HOIP-based solar cells has reached above 22%, an efficiency comparable to that of standard polycrystalline silicon solar cells.