How Does CIGS Performance Depend on Temperature at the Microscale?

Abstract

Unveiling the correlation among electrical performance, elemental distribution, and defects at the microscale is crucial for the understanding and improvement of the overall solar cell performance. While this is true in general for solar cells with polycrystalline absorber layers, it is particularly critical for defect engineering of the complex quaternary CuIn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">∞</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-∞</sub> Se <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (CIGS) material system. Studying these relationships under standard ambient conditions can provide important insights but does not provide input on the behavior of the cell under real operating conditions. In this contribution, we take a close look at the complex temperature dependence of defects and voltage in CIGS at the microscale. We have developed correlative X-ray microscopy methods and adapted them for temperature-dependent measurements of the locally generated voltage and elemental compositions at the microscale. We have applied these techniques to industrial CIGS solar cells covering temperatures from room temperature up to 100 °C. We find underperforming areas spanning multiple grains that do not correlate with the elemental distribution of major absorber constituents. However, we demonstrate that low-performing areas perform better at higher temperatures relative to the high-performing areas.