Researchers in Australia have resolved a fundamental challenge preventing the wide uptake of next-generation perovskite solar cells.
Metal-halide perovskites, a class of hybrid organic-inorganic materials, provide a cheap, flexible and highly promising pathway for efficient solar photovoltaics, as well as light emissive devices and fast X-ray detectors.
However, since gaining prominence over the last decade, perovskite materials have presented scientists and engineers with several problems precluding their widespread use in commercial applications.
Among these is light-induced phase segregation, in which illumination, such as sunlight, disrupts the carefully arranged composition of elements within mixed-halide perovskites.
This in turn leads to instability in the material’s bandgap, interfering with the wavelengths of light absorbed, while reducing charge-carrier conduction and the efficiency of devices.
Now, though, an unlikely solution has been identified.
Members of the ARC Centre of Excellence in Exciton Science have shown that high-intensity light will undo the disruption caused by light at lower intensities, and that this approach can be used to actively control the material’s bandgap.
The results have been published in the journal Nature Materials.
Dr. Chris Hall, a member of Professor Trevor Smith’s team at The University of Melbourne, and Dr. Wenxin Mao of Professor Udo Bach’s group at Monash University, first noticed the potential to explore this avenue of investigation during a separate experiment.
“It was one of those unusual discoveries that you sometimes hear about in science,” Chris said.
“We were performing a measurement, looking for something else, and then we came across this process that at the time seemed quite strange. However, we quickly realised it was an important observation.”
They enlisted the help of Dr. Stefano Bernardi, a member of Dr. Asaph Widmer-Cooper’s group at the University of Sydney, who led the computational modelling work to better understand their surprising solution to the issue.
Stefano said: “What we found is that as you increase the excitation intensity, the local strains in the ionic lattice, which were the original cause of segregation, start to merge together. When this happens, the local deformations that drove segregation disappear.
“On a normal sunny day, the intensity is so low that these deformations are still localised. But if you find a way