The objective of this study is to find the key factors to improve V(oc). In this study, pentanary Cu(InGa)(SeS)(2) absorbers were prepared by selenization and sulfurization or a sulfurization after selenization (SAS) method. It is found that the "sulfurization degree" defined as a function of temperature and holding time at the sulfurization step is a key factor to enhance the Ga diffusion and improve V(oc). It is also verified that increase in the temperature difference between selenization and sulfurization enhances the incorporation of S into the selenide absorber. Applying these findings related to Ga and S, V(oc) of 642 mV/cell and efficiency of 14.3% are achieved on a 30 cm x 30 cm-sized soda-lime glass substrate. (C) 2009 Published by Elsevier B.V.