CIS Photovoltaic Technology: Final Report, 12 January 1997--15 April 1998

This report describes work performed by Energy Photovoltaics, Inc. (EPV) during the third phase of a three-phase, cost-shared subcontract. Researchers at EPV explored novel sequential formation recipes for CIGS that can be implemented on a unique pilot line constructed to coat low-cost, glass substrates 4300 cm2 in area; implemented a particular CIGS recipe on the pilot line that enabledlarge-area modules to be prepared with efficiencies up to 7.6%; and performed electrical resistance monitoring of the film that proved capable of indicating the temperature of compound formation and detecting termination. The substrate/Mo/Na working group (which included EPV, NREL, and others) studied Na in Mo and the effect of Na on devices, and found it beneficial except at concentrationsexceeding 0.4%. Researchers determined the following properties of large-area, magnetron-sputtered ZnO:Al: sheet resistance 24 ohm/sq., transmission 82%, conductivity 440 S cm-1; and preheating the glass increases the conductivity. Devices prepared using a baseline CIGS process averaged 11.7% in efficiency. Modules and minimodules were prepared using a diode-laser-pumped yttrium-aluminum-garnetlaser for the Mo patterning and mechanical scribing for the cuts. Large-area CIGS formation involves the use of linear sources, and thickness profiles were presented for simple and optimized linear sources. An unencapsulated module producing 25 watts (7.65% aperture-area efficiency) was produced. Using a new diagnostic technique, the fill factor of a CIGS module was decomposed into contributionsfrom the intrinsic device fill factor and ZnO sheet resistance.