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In this paper, we report the development of Cd-free buffers using atomic layer deposition (ALD) for Cu(In,Ga)(S,Se)₂-based solar cells. The ALD process gives good control of thickness and the S/S +O ratio content of the films. The influence of the growth per cycle (GPC) and the S/(S+O) ratio, and the glass temperature of the atomic layer deposited Zn(O,S) buffer layers on the efficiency of the Cu(In,Ga)(S,Se)₂ solar cells were investigated. We present the first results from our work on cadmium-free CIGS solar cells on substrates with an aperture area of 0.4 cm². These Zn(O,S) layers were deposited by atomic layer deposition at 120 °C with S/Zn ratios of 0.7, and layers of around 30 nm. The Zn(O,S) 20% (Pulse Ratio: H₂S/H₂O+H₂S) process results in a S/Zn ratio of 0.7. We achieved independently certified aperture area efficiencies of 17.1% for 0.4 cm² cells.