A method for forming an organic material layer on a substrate in an in-line deposition system is disclosed. In one aspect, the organic material is deposited with a predetermined non-constant deposition rate profile, which includes a first predetermined deposition rate range provided to deposit at least a first monolayer of the organic material layer with a first predetermined average deposition rate and a second predetermined deposition rate range provided to deposit at least a second monolayer of the organic material layer with a second predetermined average deposition rate. The injection of organic material through the openings of the injector is controlled for realizing the predetermined deposition rate profile.