Transmission Electron Microscopy Study on Degradation Mechanism of CdTe Thin-Film Solar Cells

In this work, we used transmission electron microscopy in a structural and chemical study on CdTe thin-film solar cells with different degradation degrees from the same photovoltaic module. We found that in the most-degraded CdTe solar cell, the accumulation of Na is precisely localized in the discontinuous part of the CdS layer. The local concentration of Na is determined to be similar to 18 at.%. This could be the root-cause degradation mechanism in CdTe thin-film solar cells. In addition, the notable accumulation of Na at the TCO/SLG interface could be responsible for the delamination of the TCO layer from the SLG substrate.