Impact of the Cu-poor to Cu-rich transition speed and Mo back contact porosity on the electrical and structural properties of CIGS-based solar cells

The influence of the transition speed from low to high copper content and two different contents of sodium in the 3-stage co-evaporation process on the Cu(In, Ga)Se₂ solar cells has been carefully analyzed. In this work we present results of the electrical and structural measurements of samples deposited under such conditions. From the current-voltage curves we infer the impact of the transition speed and sodium content on the transport mechanism and relative content of the metastable defects. Results of the IQE and XRD measurements indicate the possible difference between slow and fast transition in the band gap grading.