Abstract
Cu(In, Ga ) Se2 (CIGS)-based solar cell is one of the most promising candidates for future photo-voltaic application. In this thesis, we developed a one-step sputtering process from a single quaternary target. This straightforward process might be suitable for large-area application in industry. In this work, CIGS thin films were fabricated by sputtering from a single target at elevated temperature without additional selenium supply. Both film properties and device properties were investigated. Two targets with different composition were studied, namely, one copper-poor target and one copper-rich target. In the study concerning copper-poor target, we found that grain boundary passivation was quite critical. Hence, additional efforts were put into sodium incorporation. For the copper-rich target, the efficiency of 6\% was achieved. However, high carrier concentration and high copper concentration might limit the device performance. For the copper-poor target, the conversion efficiency was increased from 0.2\% to over 7.5\% by controlling sodium composition.