Role of incorporated sulfur into the surface of Cu(InGa)Se-2 thin-film absorber

High-performance Cu(InGa)Se-2 (CIGS) thin-film absorbers with an intentiona lly graded band-gap structure have been fabricated by a simple two-stage me thod using In/Cu-Ga/Mo stacked precursors and H2Se gas. Additional sulfuriz ation step to form a thin Cu(InGa)(SeS)(2) (CIGSS) surface layer on the abs orber is necesarry to improve the device performance. In order to understan d the role of S incorporated into CIGS absorber, approaches with S are disc ussed. One approach is carried out by changing the condition of our absorbe r formation process. It is verified to be possible to incorporate more S in to the CIGS absorber, but difficult to improve the device performance with higher S contained CIGS absorbers because of decrease in FF. The incorporat ed S is concluded to be effective to improve the pn heterojunction quality due to the passivation of surface and grain boundary of CIGS absorber throu gh the formation of a thin CIGSS surface layer. (C) 2001 Elsevier Science B .V. All rights reserved.