(Invited) CdTe Photovoltaic Devices Grown Directly on Transparent Carbon Single Wall Nanotube Back Contacts

CdTe/CdS solar cells were fabricated directly on 25 nm thick carbon single wall nanotube (SWNT) back contacts without the use of copper. Layers were deposited using a commercial, high temperature deposition process, and devices were finished with CdS layers grown by vapor assisted transport and chemical bath deposition.  The inclusion of the thin SWNT layer was absolutely essential for good device performance.  Device efficiencies were high despite the fact that the SWNT layer was supported on an n-type SnO₂ layer that introduced a secondary n/p junction at the rear of the device. The champion device had an efficiency of 7.53%, which is close to the record value of 7.8% for a Cu-free substrate configuration device.[1] The use of a partially transparent back contact allowed comparison of device performance with front and backside illumination, which revealed several novel features of the SWNT back contact.

This work was supported by the U.S. Department of Energy under Award Number DE-SC0006349 and by faculty start-up funds from the University of Toledo.  We gratefully acknowledge samples and assistance from Mark D. Dorogi, Syed Zafar, and Gary T. Faykosh of Willard and Kelsey Solar Group.

(1)  I. Matulionis, S. Han, J. A. Drayton, K. J. Price, A. D. Compaan, MRS Online Proceedings Library 2001, 668, H8.23.