Direct evidence of a buried homojunction in Cu(In,Ga)Se2 solar cells

The built-in electrical potential of Cu(In,Ga)Se-2 (CIGS) solar cells was measured quantitatively and resolved spatially using scanning Kelvin probe microscopy. Profiles of the electrical potential along cross sections of the device demonstrate that the p-n junction is a buried homojunction, and the p/n boundary is located 30-80 nm from the CIGS/CdS interface in the CIGS film. The built-in electric field terminates at the CIGS/CdS interface, indicating that the CdS and ZnO layers of the device structure are inactive for the collection of photoexcited carriers. (C) 2003 American Institute of Physics.