“The basis of the technique is microscopy but merging it with frequency analysis. We use a laser beam and we focus on a spot and scan across the device to measure the quality of the solar cell. This new method allows us to do imaging analysis of whole or complete solar cells and look at how they perform, how they change with time and aging, and how good a solar cell they are,” Laird said in a release.
Other than partners at Monash University, a team from Oxford University has already sent samples of cutting-edge prototypes to be tested by Laird’s machine. Members of the University of Sydney working on experimental solar cells for satellites and other space vehicles are also on the waiting list.
“You can’t have a solar cell that decomposes quickly when it’s meant to last 20 years in the field. This is a missing link in the repertoire of techniques we have to throw at that problem,” Laird added.
In this report, a large-area laser beam-induced current microscope that has been adapted to perform intensity modulated photocurrent spectroscopy (IMPS) in an imaging mode is described. Microscopy-based IMPS method provides a spatial resolution of the frequency domain response of the solar cell, allowing correlation of the optoelectronic response with a particular interface, bulk material, specific transport layer, or transport parameter. The system is applied to study degradation effects in back-contact perovskite cells where it is found to readily differentiate areas based on their markedly different frequency response. Using the diffusion-recombination model, the IMPS response is 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 is used to calculate spatial maps of the carrier ambipolar diffusion length. The observed frequency response of IMPS images is then discussed.