Crystallization and photophysical dynamics of Tris(8-hydroxyquinoline) aluminum crystals fabricated by micro-spacing sublimation method

The crystallization and photophysical properties of organic semiconductors have a great influence on the device performance. In this work, micro-spacing sublimation method was used to regulate the crystallization and optical properties of tris(8-hydroxyquinoline) aluminum (Alq3) molecules. It is found that when Alq3 gas molecules contact with the cold substrate, Alq3 molecules aggregate to form small nuclei, and then grow into fiber struc-ture. Micro-spacing distance supplies enough time for Alq3 molecules to assembly into ordered structure. The fibers will further grow to large crystals with the increase of deposition time. The density of trap states is significantly reduced as the crystal size increases owing to the strong 7L-7L molecule interactions, leading to the higher luminescence efficiency. This work will be beneficial to the preparation of organic semiconductor crystals and study of their crystallization process, thus applied to the optimization of device performance.