Comparison of the potential distributions at grain boundaries on the surface and in the depth of the absorber in Cu(In, Ga)Se2 thin-film solar cells

Grain boundaries in the Cu(In, Ga)Se₂ absorber layer are investigated applying Kelvin probe force microscopy. Potential distributions at grain boundaries on the absorber surface and on untreated cross section of the solar cell are compared. Depending on potential variation, three types of grain boundaries can be classified at the absorber surface, while a single type of grain boundaries with much smaller potential variations is identified at the cross section. This result suggests the electrically neutral properties of most of the buried grain boundaries in the absorber.