Dependence of defect signature on conductivity of polycrystalline Cu(In,Ga)Se2 layers by photocurrent spectroscopy

Photocurrent spectroscopy - a method sensitive only to bulk levels - was used to investigate defect spectrum of CIGS polycrystalline films. Low temperature signal, previously labeled E4, with parameters similar to the N1 was observed in all samples, irrespective of their preparation details. We show that sensitivity to the hole concentration is its characteristic feature. Similar dependence of emission rates on doping changes induced by light soaking has been commonly observed for N1 level in solar cells. Our findings point toward common origin for the N1 level and E4 signal observed by photocurrent methods in the epitaxial and polycrystalline CIGS.