Structural, thermo-optical, and photophysical properties of highly oriented thin films of quinoxalinophenanthrophenazine derivative

Abstract

The structural, thermo-optical, and anisotropic photophysical properties of highly oriented thin solid films of 2,11-bis(1,1-dimethylethyl)-6,7,15,16- tetrakis(dodecyloxy)quinoxalino[2′,3′:9,10]phenanthro[4,5-abc] phenazine (TQPP-OC12) prepared by a zone-casting method are discussed. The films were obtained on glass substrate by solution processing. The in-plane alignment of TQPP-OC12 molecules in the formed layers was studied by X-ray diffraction methods, optical polarized microscopy combined with thermo-optical analysis, atomic force microscopy (AFM), and UV-vis absorption and fluorescence spectroscopy both with polarized light methods. The high molecular order of zone-casted TQPP-OC12 was studied in conjunction with the observed abundance of phase transitions as a function of thermal conditions to assess the material's suitability for optoelectronic device applications. The molecular disk planes in the as-cast samples are parallel to the casting direction and orient almost perpendicularly (∼96°) to the substrate. Continuous films with a thickness of 200-300 nm are formed from lamellas arranged parallel to the surface. All observed phase transitions have crystal-crystal character; however, molecular primary arrangement remains basically identical for all processing conditions. Sample annealing destroys the multiple polymorphs observed in the as-cast sample and leads to an increase of molecular ordering. © 2014 American Chemical Society.