Band alignment of CBD deposited Zn(O,S)/Cu(In1−xGax)Se2 interface

Chemical bath deposition (CBD) Zn(O,S) buffer layers grown on Cu(In1−xGax)Se2 (CIGS) thin films have recently surpassed CdS in high efficiency cells (20.9%). A critical component of a CIGS device is the buffer layer - the layer that is found between the absorber CIGS layer and the ZnO window layer. Although CBD CdS is an effective buffer layer and traditionally used for devices, it is not entirely effective for high bandgap absorber films. The Zn(O,S)/CIGS interface was studied by X-ray photoelectron spectroscopy to reveal the valence band offset (VBO) and conduction band offset (CBO) as −1.15 eV and 1.17 eV respectively. Band bending that accompanies junction formation is also characterized in both layers.