Star-shaped Organic Molecules That Comprise a 1,3,5-Trisubstituted Benzene Core and Three Oligoaryleneethynylene Arms as Light-emitting Materials

Star-shaped rigid molecules that comprise a 1,3,5-trisubstitued benzene core and three oligoaryleneethynylene arms have great potential application in organic light-emitting devices (OLEDs). Their optical and electronic properties are tuned by the star-shaped molecular size. To reveal the relationship between the properties and structures, we perform a systemic investigation for these organic molecules. The ground and excited state molecules are studied using density functional theory (DFT), the ab initio HF, and the single excitation configuration interaction (CIS), respectively. And the electronic absorption and emission spectra are investigated with time-dependent density functional theory (TDDFT) and Zerner's intermediate neglect of differential overlap (ZINDO) methods. The results show that the HOMOs, LUMOs, energy gaps, ionization potentials (IP), electron affinities (EA), absorption and emission spectra are controlled by the star-shaped molecular size, which favor the hole and electron injection into OLEDs. With increasing the molecular conjugated length, the absorption and emission spectra exhibit red shifts to some extent and are in good agreement with the experimental ones. Also, the calculated emission spectra range from 330 to 440 nm. All the calculated show that the star-shaped molecules are promising as blue light emitting materials