Interface-Barrier-Induced J-V Distortion of CIGS Cells With Sputtered-Deposited Zn(S,O) Window Layers

• Published in: IEEE journal of photovoltaics Vol. 4; no. 3; pp. 942 - 947
• Main Authors: Tao Song, McGoffin, J. Tyler, Sites, James R.
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.05.2014; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Charge carrier density; Charge carrier processes; Cu(In; current-voltage (J-V) distortion; Ga)Se _{2} (CIGS; Lighting; Photoconductivity; Photonics; Photovoltaic cells; Solar energy; sputtering; Temperature measurement; thin films; Zn(S
• DOI: 10.1109/JPHOTOV.2014.2301894
• ISSN: 2156-3381

Sputtered-deposited Zn(S,O) is an attractive alternative to CdS for the window layer of Cu(In,Ga)Se 2 (CIGS) thin-film solar cells due to its higher band gap, which allows greater blue-photon collection. However, distortions to current-voltage ( J-V) curves are observed in some cases. A straightforward photodiode model with a secondary barrier at the Zn(S,O)/CIGS interface is employed to explain the physical mechanisms of the experimental J-V distortions. The primary contributor to the secondary barrier is the conduction-band offset (CBO), whose magnitude is determined by the oxygen fraction in Zn(S,O) and by the carrier density of Zn(S,O); the latter may be increased with indium-doping. Comparison of experimental and simulated J-V characteristics with variation in oxygen fraction, window carrier density, and temperature, allows a reasonably compelling test of the secondary-barrier model for this system.