Properties of tris (8-hydroxyquinoline) aluminum thin films fabricated by spin coating from static and dynamic dispense methods

Abstract Thin films of Tris-(8-hydroxyquinoline) aluminum (Alq3) were prepared from a solution dissolved in chloroform by spin coating technique on glass substrates with two different dispense methods. Analysis of Atomic Force Microscopy data revealed that the formation of granular features in thin films of Alq3 which depends on the method of dispense. Broader height and size distributions have been observed for the films prepared from the static dispense method with a mean granular height of 30 nm and radius spread out to a large range from 25 to 175 nm with a mean value 130 nm. For the films prepared from the dynamic dispense method it was found that there exists a higher granular formation density, with the mean height and radius of particles being 31 and 92 nm respectively with more confined distributions. The HOMO-LUMO energy gap was estimated from Tauc plots. Films prepared from the static dispense method, the energy gap was 2.78 eV, while films prepared using the dynamic dispense method featured an energy gap of 2.95 eV. The larger energy gap can be attributed to the smaller particle size of films prepared with the dynamic dispense method.