Near-field scanning optical microscopy studies of Cu(In,Ga)Se-2 solar cells

A near-field scanning optical microscope (NSOM) is used to study the local photoresponse of Cu(In,Ga)Se-2 thin film solar cells. The grain boundaries of the small grains (<1 mu m) show some reduction in photoresponse; however the photoresponse is significantly reduced near most crevices separating large grains (>10 mu m). In addition, NSOM images show response variations from grain to grain and areas of reduced photoresponse which have no corresponding topography. Photovoltage imaging of the cleaved side of the solar cells reveals the depth and nonuniformities of the actual p-n junction. It is found that the response of the p-n junction varies on a 0.5 mu m length scale. (C) 1997 American Institute of Physics.