Electrical Modification in Cu(In,Ga)Se2 Thin Films by Chemical Bath Deposition Process of CdS Films

We have measured the two-dimensional electrical potential distribution on the surface of photovoltaic Cu (In,Ga) Se2 (CIGS) thin films using the nanoscale electrical characterization of scanning Kelvin probe microscopy. The potential peak on the grain boundaries becomes sharper after the sample is rinsed in high-purity water, and the height of the potential peak becomes smaller after chemical treatments in a solution similar to that used in the chemical bath deposition of CdS films. This demonstrates an effect of surface Na removal by the water rinsing and downward band bending on the CIGS film surface induced by the chemical treatment. This electrical modification is expected to benefit the properties of the electrical junction and, hence, CIGS/CdS device performance.