Characterization of surface potential and capacitance on CdS/Cu(In,Ga)Se2 multi-layers by KFM and EFM

Kelvin probe force microscopy (KFM) and electrostatic force microscopy (EFM) have been performed to investigate surface potential and depletion capacitance distribution on CdS/Cu(In,Ga)Se₂ [CdS/CIGS] multi-layers. In KFM, potential lowering and capacitance increase were observed especially around GBs, which indicates that the acceptor density originating from copper vacancy VCu increases in CIGS and that the near-surface donor states originating from anti-site defect CdCu are concentrated around GBs. In addition, the electrostatic force spectra measured by EFM suggest that Cd diffusion into CIGS layer is enhanced around GBs.