How grain boundaries in Cu(In,Ga)Se2 thin films are charged: Revisit

Potential measurements on Cu(In,Ga)Se-2 thin films using scanning Kelvin probe force microscopy have been reported extensively to address grain-boundary (GB) recombination by examining GB charging. However, the results are highly inconsistent. We revisit this issue by measuring high-and low-quality wide-bandgap films and using a complementary method of scanning capacitance microscopy. Our results show consistent positively charged GBs in our high-quality films with minimal surface defects, except for the Sigma 3[112] GBs, which are charge neutral. We discuss possible artifacts due to surface defects when examining the GB charging and the role of GBs in the device performance. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737406]