An investigation of band profile around the grain boundary of Cu(InGa)Se2 solar cell material by scanning probe microscopy

We performed scanning tunneling spectroscopy on an as-grown Cu(InGa)Se2 (CIGS) thin film and photo-assisted Kelvin probe force microscopy on a CIGS solar cell. From these measurements, we estimated the band profile around the grain boundaries (GBs). The results indicate both downward bending of the conduction band edge and broadening of the band gap near GBs. We can therefore conclude that photo-generated electrons and holes are easily separated by the built-in field near GBs, and consequently their recombination at the GBs should be suppressed. Copyright (c) 2011 John Wiley & Sons, Ltd.