In general, defects in grain boundaries in polycrystalline materials form effective recombination centers. However, this was not the case for polycrystalline Cu(In,Ga)Se2 thin films used in solar cells. It was difficult to determine grain boundary properties by electron back-scatter diffraction and electron-beam-induced current measurements because of the surface roughness of as-grown Cu(In,Ga)Se2 films. In this study, the Cu(In,Ga)Se2 film surface was flattened by ion milling, and then the grain boundary character distribution and spatial distribution of electronically active defects were determined by electron back-scatter diffraction and electron-beam-induced current measurements, respectively. Results suggested that flattening the Cu(In,Ga)Se2 film surface enabled the measurements of intrinsic grain boundary properties. Moreover, the results revealed that the grain boundary character distribution on the Cu(In,Ga)Se2 film surface hardly changed in the band gap energy range less than 1.28eV.

Grain Boundary Character Distribution on the Surface of Cu(In,Ga)Se2 Thin Film. T.Minemoto, Y.Wakisaka, H.Takakura: Japanese Journal of Applied Physics, 2011, 50[3], 031203