Fabrication of a Complete Photovoltaic CIGS Device by Electrodeposition

Copper Indium Gallium Selenium (CIGS) films are attractive for photovoltaic applications due to their high optical absorption coefficient. Generation of CIGS films by electrodeposition is particularly appealing due to the relatively low capital cost and the relatively high throughput^1-3. Numerous publications address the electrodeposition of CIGS; however, to our knowledge, none reports the fabrication of a complete CIGS photovoltaic cell using electrochemical techniques.

In this work we introduce electrochemical processes that enable the fabrication of complete CIGS and CIGSS functional photovoltaic devices, based entirely on electroplating. The electrodeposition of the CIGS or CIGSS absorber layers is based on an electrolyte that is far more dilute than systems that had been traditionally used, and which yields much improved CIGS and CIGSS films^4,5. In addition to the absorber layer, electrochemical processes for the electrodeposition of the cadmium sulfide (50 nm), and the pure zinc oxide (100 nm) layer are described. Also the electrodeposition of doped zinc oxide (0.5 µ) (window layer) is discussed. The substrate has been stainless steel coated with electrodeposited metal barrier (Ni, Cr, or Cu), enabling continuous strip plating. An intermediate molybdenum layer, providing improved interface to the absorber layer, increased the efficiency. The final device structure is shown in figure 1.

Complete electrodeposited devices were generated and tested exhibiting efficiencies ranging from 2 to 6% with quantum efficiency exceeding 0.6 as shown in figure 2. A comprehensive electrochemical process such as described here, will enable the fabrication of the entire device through a fast wet chemical process, providing effective manufacturing integration and scaling.