Atomic layer deposition (ALD) of ZnO and indium sulfide layers has been investigated. In situ monitoring at the monolayer level has been made by using quartz crystal microgravimetry (QCM), with a special focus on extrinsic doping of ZnO with Al. Cu(In,Ga)Se-2/In2S3 (ALE)/ZnO (ALE) cells present efficiencies up to 13.5%. Indium sulfide layers used in these cells are characterized by a high band-gap value (up to 3.3 eV). They possess an amorphous like structure and a composition close to In,S, as determined by Rutherford Back Scattering measurements. Lowering of the band-gap and crystallization take place under annealing, indicating that the high band-gap value of ALE indium sulfide layer is most likely related to structural effects.