Researchers from the University of Melbourne, Monash University and IEK-5 Photovoltaik in Germany have developed a large-area laser beam induced current microscope that has been adapted to perform intensity modulated photocurrent spectroscopy (IMPS) in an imaging mode. The new imaging tool could reportedly spot previously undetectable defects in solar cells.
The team's IMPS microscopy was used to study the spatial dependence of moisture-related degradation in a back-contact PSC. Using diffusion-recombination theory, the researchers modeled the IMPS response from which ambipolar diffusion length maps can be extracted from low-frequency experimental data. Apart from this important metric, they illustrated how other frequency bands can be used to study the degradation of a PSC.
The new system was applied to study degradation effects in back-contact perovskite cells where it was found to differentiate areas based on their markedly different frequency response. Using the diffusion-recombination model, the IMPS response was modeled for a sandwich structure and extended for the special case of lateral diffusion in a back-contact cell. In the low-frequency limit, the model was used to calculate spatial maps of the carrier ambipolar diffusion length.
It was said that the newly developed machine worked so well, that a team from Oxford University has decided to use it to test prototype solar cells, while a University of Sydney team is also working with the developers to use the machine to analyze solar cells for space technology.
The new imaging tool can analyze any solar material, but specializes in perovskites. By identifying various problems in these materials, the team hopes the new machine can go some way to solving them, allowing scientists to utilize the low-cost material in solar panels. The new device uses a special laser and microscope to map the problems that cause a perovskite solar cell to break down, in a way that no other machine has achieved thus far, according to the team.
“This machine is doing things a bit differently compared to other machines,” said Jamie Laird, a research fellow at the ARC Centre of Excellence in Exciton Science and the University of Melbourne.
