The use of Ga in two-step processing to optimize the electronic properties of CuIn/sub x/Ga/sub 1-x/Se/sub 2/ solar cells

We have developed techniques for effectively incorporating Ga in CIGS within the confines of our manufacturing-friendly process. Near Cu/(In+Ga)=1 collection lengths of 1-2 /spl mu/m can be attained resulting in consistent Jsc's of 40 mA/cm/sup 2/. As the metal ratio is decreased below 1, there is an unusual abrupt increase in Eg of 50 mV and a significant deterioration of electronic properties. These properties are discussed in terms of interplay between process control of kinetics and thermodynamics and the dictates of the phase diagram. A key objective which we have attained is the ability to independently optimize surface and bulk properties. Using these techniques we have raised our Voc's above 500 mV for devices with band gaps of 0.95 eV and have achieved 13% device efficiency.