Electron-beam induced degradation in CdTe photovoltaics

We used electron beam induced current (EBIC) to measure degradation of CdTe photovoltaic cells. We have observed that: (i) the EBIC signal shows a considerable, continuous degradation depending on the electron-beam current, scan area, energy, and sample treatment; (ii) the characteristic degradation time fluctuates between different spots on the same sample; and (iii) grain boundary regions are the most effective collectors of the electron-beam generated charge carriers. Our phenomenological model relates the observed degradation to defects caused by the electron-beam generated electrons and holes.