Materials and processing issues in thin-film Cu (In, Ga) Se[sub 2]-based solar cells

Abstract

We have fabricated-high efficiency, Cu(In,Ga)Se2 (CIGS)-based photovoltaic (PV) devices by four different processes. Each process may be characterized as either sequential or concurrent deposition of the metals with or without an activity of Se. A world-record, total-area efficiency of 17.7% has been achieved by the concurrent delivery of the metals in the presence of Se. Ga has been introduced into the device in a such a manner as to produce homogeneous, normal profiling, and double-profiling graded band gap structures. This has resulted in an open-circuit voltage (Voc) parameter of 680 mV and a fill-factor over 78%. The quality of CIGS-based films and devices is becoming decoupled from the method of film delivery. This leads to novel, fast, and low-cost methods for absorber fabrications. Two such deposition techniques, sputtering and electrodeposition, will also be discussed and results to date presented. Finally, a fabrication model has been developed allowing for simple translation of these processes to a manufacturing environment for the large-scale production of modules.