  While producing comparable efficiencies and showing similar properties when
probed by conventional techniques, such as Raman, photoluminescence and X-ray
diffraction, two thin film solar cell materials with complex structures, such
as quaternary compound CZTSe, may in fact differ significantly in their
microscopic structures. In this work, laser induced modification Raman
spectroscopy, coupled with high spatial resolution and high temperature
capability, is demonstrated as an effective tool to obtain important structure
information beyond that the conventional characterization techniques can offer,
and thus to reveal the microscopic scale variations between nominally similar
alloys. Specifically, CZTSe films prepared by sputtering and co-evaporation
methods that exhibited similar Raman and XRD features were found to behave very
differently under high laser power and high temperature Raman probe, because
the differences in their microscopic structures lead to different structure
modifications in response to the external stimuli, such as light illumination
and temperature. They were also shown to undergo different degree of plastic
changes and have different thermal conductivities as revealed by
spatially-resolved Raman spectroscopy.
