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

Abstract

The built-in electrical potential of Cu(In,Ga)Se2 (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.