Deep Levels and Space Charge Distribution in Cu(In,Ga)Se 2 Photovoltaic Devices

ZnO/CdS/Cu(In,Ga)Se 2 photovoltaic devices have been investigated at low temperatures after the samples have been subjected to various forward and reverse biases or illumination at room temperature and during cool-down. The C-V characteristics has been measured and interpreted as distorted by a charge captured in more than 2-10 22 m -3 of deep traps. Subsequent illumination by use of red and blue light reveals very high concentration of midgap centers in the 10-20 nm layer of absorber close to the heterointerface. Their presence might be a source of efficiency losses previously attributed to the defects in CdS.