A study on the optoelectronic properties of CuIn1-xGaxSe2 grain boundaries by electrostatic force microscopy

We investigated the electric charge distribution in CuIn_1-x Ga_xSe₂ films, with particular emphasis on grain boundaries. Hall measurements, electron beam-induced current and optical beam-induced current measurements are commonly used for the characterization of solar cells, but they do not provide the resolution necessary for the investigation of individual grain boundaries. Therefore, we used an electrostatic force microscopy (EFM) capable of probing the electric charge distribution and the potential gradient of sample surface. EFM experiments were performed at 300 K with a Dimension trade 3100 scanning probe microscope (Digital Instruments). We suggest that grain boundaries should be electron-accumulated area and the inner grain area be the hole-accumulated area. The potential variations between the grain boundaries and inner grain area were estimated to be 60~180 meV