Influence of Cu(In,Ga)(Se,S)₂ surface treatments on the properties of 30 × 30 cm² large area modules with atomic layer deposited Zn(O,S) buffers

We report the effect of Cu(In,Ga)(Se,S)₂ absorber surface treatments on the properties of atomic layer deposited-Zn(O,S) buffered 30 × 30 cm² large area modules. The absorber is prepared by the sequential process. H₂O and KCN solution treatments are investigated. The absorber surface treatment is found to influence significantly the open circuit voltage and the fill factor of the full modules. Light soaking related metastabilities are also found to depend on the type of treatment. While both H₂O and KCN treatments are efficient at removing Se-oxides and Na₂HCO₃, the KCN treatment is found to remove additionally Ga-oxides and elemental Se that are detected on the surface of the absorber. A 30 × 30 cm² module aperture efficiency up to 12.3% could be achieved with KCN surface treatment of the absorber. - Highlights: • The Cu(In,Ga)(Se,S)₂ surface influences the Zn(O,S)-buffered module performance. • Surface treatment by H₂O efficiently removes Se-oxides and sodium compounds. • KCN treatment of the absorber removes Se-oxides, Ga-oxides and elemental Se. • The devices' light soaking behavior depends on the absorber's surface chemistry. • A 30 × 30 cm² module efficiency of 12.3% is achieved with KCN treatment