Model for electronic transport in Cu(In,Ga)Se2 solar cells

✍ Scribed by A. Niemegeers; M. Burgelman; R. Herberholz; U. Rau; D. Hariskos; H.-W. Schock

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 211 KB
• Volume: 6
• Category: Article
• ISSN: 1062-7995
• DOI: 10.1002/(sici)1099-159x(199811/12)6:6<407::aid-pip230>3.0.co;2-u

✦ Synopsis

Temperature-dependent measurements of the current±voltage characteristics and of the junction admittance of ZnO/CdS/Cu(In,Ga)Se 2 heterojunction solar cells are presented, together with numerical modelling of these experimental results. We explain the cross-over between dark and illuminated current±voltage characteristics currently observed for this type of device by the impact of the defect chalcopyrite layer at the surface of the Cu(In,Ga)Se 2 absorber. Our model assumes an illumination-dependent voltage drop across a defect layer with a thickness of 15 nm to explain the cross-over. The voltage drop results from the electrical dipole made up of donor-like states at the interface between the defect layer and CdS and deep acceptor states in the defect layer itself. The illumination dependence of this voltage drop is explained by photogenerated holes trapped by the deep acceptor states in the defect layer. Numerical simulations have been carried out using the program SCAPS-1D in order to verify our model assumptions. From our model, indirect conclusions are derived concerning the maximum conduction band osets between CdS and the defect layer and between CdS and ZnO.