Atomic Layer Epitaxy, ALE, has been applied to grow CdS/CdTe-thin film solar cells. ALE offers the possibility to grow both CdS and CdTe in a single process and to taylor the interface of CdS and CdTe. The thickness of CdS was varied and the optimum was found to be in the range of 50-100 nm with good heterojunction performance and CdTe-crystallinity leading to excellent PV-properties. The structures with thinner CdS layers suffered low open circuit voltage but on the other hand with thicker CdS the short circuit current was limited by the absorption of CdS.