Theoretical Design Of Blue Emitting Materials Based On Spirosilabifluorene Derivatives

Spirobifluorene derivatives have many kinds of applications such as in OLEDs. Compared with spirobifluorene, spirosilabifluorene may have an improved morphological stability in films. Identifying the relation between electronic excitation properties and the chemical as well as the geometrical structures is the key tool for a directed design of new electronic compounds and tuning of their photo electronic properties. Although this task can be addressed from the theoretical standpoint, a few computational works relating to this type of materials can be found in the literature. In this contribution, we design new photoluminescence materials based on the selected approaches for spirosilabifluorene based materials.To better understand the substitutional effect, the"CH"/N, H/R (R =–NO2,–CN,–NH2 and–OCH3) substituted spirosilabifluorene derivatives are investigated. Equilibrium ground state geometry configurations and their relevant electronic properties of these derivatives are calculated by HF/6-31G* method. Their first excited state geometries are investigated using CIS/6-31G* method. The optical properties for designed molecules are investigated by TD-B3LYP/6-31G* approach. According to our results, the structures do not show any appreciable change. In comparison with the parent molecule, significant red-shift is predicted for the emission spectra of the di-substituted derivatives with–NH2 (96nm),–OCH3 (61nm) and the push-pull (containing both–NH2 and–NO2) derivative (56nm). No apparent change is however predicted for the absorption/emission wavelengths within the"CH"/N substituted derivatives, an efficient charge transfer being revealed. These properties may make these derivatives potential candidates for blue or violet-blue emitting materials. Furthermore, we find that the performance and the optical properties of these derivatives can be improved by adding aryl group, push-pull substitutents or oligomerization. The optical properties for the investigated derivatives can be explained by the distribution pattern of HOMO and LUMO and the energy gap.