Metastable electrical transport in Cu(In,Ga)Se2 thin films and ZnO/CdS/Cu(In,Ga)Se2 heterostructures☆

Abstract We ascribe the relaxation of the open circuit voltage in Cu(In,Ga)Se 2 heterojunction solar cells to persistent photoconductivity in the absorber material. The experimentally observed increase of the open circuit voltage during illumination is accompanied by an increase of the junction capacitance resulting from an effective increase of the space charge density by persistent trapping of photogenerated electrons.