The Zn(S,O,OH)/ZnMgO buffer in thin film Cu(In,Ga)(S,Se)₂-based solar cells part I: Fast chemical bath deposition of Zn(S,O,OH) buffer layers for industrial application on co-evaporated Cu(In,Ga)Se₂ and electrodeposited cuIn(S,Se)₂ solar cells

This paper is focused on the basic study and optimization of short time (<10min) Chemical Bath Deposition (CBD) of Zn(S,O,OH) buffer layers in co-evaporated Cu(In,Ga)Se₂ (CIGSe) and electrodeposited CuIn(S,Se)₂ ((ED)-CIS) solar cells for industrial applications. First, the influence of the deposition temperature is studied from theoretical solution chemistry considerations by constructing solubility diagrams of ZnS, ZnO, and Zn(OH)₂ as a function of temperature. In order to reduce the deposition time under 10 min, experimental growth deposition studies are then carried out by the in situ quartz crystal microgravimetry (QCM) technique. An optimized process is performed and compared to the classical Zn(S,O,OH) deposition. The morphology and composition of'Zn(S,O,OH) films are determined using SEM and XPS techniques. The optimized process is tested on electrodeposited-CIS and co-evaporated-CIGSe absorbers and cells are completed with (Zn,Mg)O/ZnO:Al windows layers. Efficiencies similar or even better than CBD CdS/i-ZnO reference buffer layers are obtained (15.7% for CIGSe and 8.1% for (ED)-CIS).