In this work, the impact of film thickness in thermally evaporated pentacene thin films and metal electrodes is studied. In particular, we report electrical performance and stability of un-encapsulated organic Schottky diodes. The chemical composition, surface morphology and ambient stability of the resulting films were also studied. The electrical measurements were carried out in vertical Schottky diodes and its performance and stability was evaluated as function of shelf life time. Oxygen was detected at the pentacene surface. This oxygen is the main cause of the diode degradation and attributed to diffusion of oxygen into the bulk of the pentacene films. Thicker pentacene films resulted in more stable for Schottky diodes. © 2012 Elsevier B.V.