NOVELTY - Forming an absorber layer containing Groups IB, IIA and VIA elements comprises: placing a substrate in a treatment chamber; and performing atomic layer deposition of a group IB element from a first source and a first group IIIA element from a second source and/or a second group IIIA element from a third source onto the substrate to form a film.    USE - For forming an absorber layer for an optoelectronic device (claimed), e.g. photovoltaic cell.    ADVANTAGE - In atomic layer deposition systems, wherever the reactant gases come in contact with substrate, good coating may be achieved. Consequently, atomic layer deposition may be readily scaled to coating large substrate areas in each reaction step. Thus, the throughput of an atomic layer deposition system may be increased by massively scaling the substrate surface area processed during each step. Pumping, purging and filling can be ensured to be high quality, thus minimizing loss of coating quality by intermixing gases. Although the whole process may take a considerable period of time to complete, a vast surface area of substrate may be coated at one time.    DETAILED DESCRIPTION - Forming an absorber layer containing Groups IB, IIA and VIA elements comprises: placing a substrate (106) in a treatment chamber (102); performing atomic layer deposition of a group IB element from a first source and a first group IIIA element from a second source and/or a second group IIIA element from a third source onto the substrate to form a film; annealing the film; and incorporating group VIA elements into the film to form the absorber layer having a thickness greater than 25 nm.    DESCRIPTION OF DRAWING(S) - The figure shows a three-dimensional exploded view of a high throughput atomic layer deposition system of the invention.    Treatment chamber (102)    Inner wall (103)    Carousel (104)    Outer wall (105)    Substrate (106)    Lid (107)    Gas sources (108, 110, 112)    Exhaust system (111)    Robots (114)    Stackable spacers (116)