Electrostatic force and Kelvin probe force microscopies on Cu(In,Ga)Se2 solar cells

Cu(In,Ga)Se₂ [CIGS] solar cells have been investigated by means of electrostatic force microscopy (EFM) and Kelvin probe force microscopy (KFM) to examine the existence of the sub-gap states originating from impurities and/or defects which should act as a carrier recombination center and to discuss the potential distribution which should influence on the internal photo-carrier diffusion, respectively. The KFM results indicate that the surface potential distributions depended on the Ga content in the CIGS layer, while the electrostatic force spectra acquired by EFM exhibited some discontinuities, which should be related with sub-gap states as electron traps.