In-situ stage development for high-temperature X-ray nanocharacterization of defects in solar cells

The vast majority of photovoltaic materials are highly sensitive to the presence of inhomogeneously distributed nanoscale defects, which commonly regulate the overall performance of the devices. The defects can take the form of impurities, stoichiometry variations, microstructural misalignments, and secondary phases - the majority of which are created during solar cell processing. Scientific understanding of these defects and development of defect-engineering techniques have the potential to significantly increase cell efficiencies, as well as provide a science-based approach to increase the competitiveness for the US PV industry on a dollar per installed kWh criterion. For the case of Cu(In, Ga)Se₂ devices for example, the theoretically limit sits at 30.5% efficiency [1], thus, surpassing DOE's SunShot goals for cost-competitive solar power. However, to date, CIGS laboratory scale cells have been reported to achieve only 20.3% efficiencies and modules have not crossed the 15 % certified efficiency barrier. Recent reports have suggested that these record cells are limited by non-ideal recombination and, more specifically, by an increased saturation current that seems to originate from the particular defect chemistry at structural defects. In order to understand the severe efficiency limitations that currently affect solar cell materials, it is necessary to understand in detail the role of defects and their interactions under actual operating and processing conditions. In this work we propose to develop a high-temperature, in-situ stage for X-ray microscopes, with the capabilities of temperature and ambient control. Here, we provide insight into the design and preliminary testing at the Advanced Photon Source with beam sizes ≈100nm.