Abstract
Significant structural evolution occurs during the deposition of CuInSe_{2} solar materials when the Cu content increases. We use insitu heating in a scanning transmission electron microscope to directly observe how grain boundaries migrate during heating, causing nondefected grains to consume highly defected grains. Cu substitutes for In in the near grain boundary regions, turning them into a Cu-Se phase topotactic with the CuInSe_{2} grain interiors. Together with density functional theory and molecular dynamics calculations, we reveal how this Cu-Se phase makes the grain boundaries highly mobile.
Highlights
Thin-film solar cells with CuðIn; GaÞSe2 (CIGS) absorber layers have reached conversion efficiencies of up to 23.35% [1,2,3,4,5,6]
We use in situ heating in a scanning transmission electron microscope to directly observe how grain boundaries migrate during heating, causing nondefected grains to consume highly defected grains
Together with density functional theory and molecular dynamics calculations, we reveal how this Cu-Se phase makes the grain boundaries highly mobile
Summary
Thin-film solar cells with CuðIn; GaÞSe2 (CIGS) absorber layers have reached conversion efficiencies of up to 23.35% [1,2,3,4,5,6]. No GB migration was observed, and the high-density planar defects within the CIS grains still remained, showing that below 450 °C an excess CS layer is essential for the GB migration.
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