Organic light emitting diodes, OLEDs, have been so much improved in the last two decades that they are being currently used in commercial applications for displays and lighting. Among many improving technologies, thermal treatments affect greatly their performances. In case the small molecule Alq3 is the active material, it was never understood why and how the temperature could have played such an important role. Now, we have discovered that such molecules tend to aggregate themselves in morphological states which are very much sensible to annealing processes, with the result of improved emission efficiency and lifetime of Alq3 thin films. Moreover, the latter ones are described by a four components model, FCM, which has been validated by degradation experiments during 6 years, a world record in its own.