Wet treatment based interface engineering for high efficiency Cu(In,Ga)Se₂ solar cells

Using atomic layer epitaxy (ALE) which is a soft deposition technique for ZnO it is possible to avoid the deposition of thick buffer layers by chemical bath deposition (CBD) and wet treatments can be almost reduced to surface treatments. In this work new electrochemical and chemical treatments have been designed with the objective of surface passivation and surface doping by using solutions with different reactivities (via pH, complexing agents, metallic cartons). ZnO layers are then deposited by ALE to complete the junctions. The results show relations between the interface treatment and the cell characteristics. Efficiencies comparable and in some cases higher than those of the reference cells made with CBD CdS and sputtered ZnO have been obtained (up to 12.7% with indium treatments).