The photophysical properties and electronic structures of bis[1]benzothieno[6,7-d:6′,7′-d′]benzo[1,2-b:4,5-b′]dithiophene (BBTBDT) derivatives as hole-transporting materials for organic light-emitting diodes (OLEDs)

Abstract

Herein, using the quantum methods DFT and TD-DFT, the optoelectronic properties and electronic structures of the eight compounds Ci (i = 1–8) based on bis[1]benzothieno[6,7-d:6′,7′-d′]benzo[1,2-b:4,5-b′]dithiophene (BBTBDT) with a D–π–D structure for Ci (i = 1–5) and D–π–A structure for Ci (i = 6–8) were investigated and discussed theoretically with the aim to apply these compounds as hole-transporting materials (HTM) in OLEDs. The electronic levels of the studied compounds calculated by B3LYP show that the proper energies of Ci (i = 6–8) match well for their efficient injection into a hole-injection layer (HIL). The compounds having the D–π–A structure appear more efficient than those having the D–π–D structure. The optoelectronic properties of the studied compounds obtained by TD-CAM-B3LYP elucidate that the C6, C7 and C8 compounds behave as electron-donating molecules and exhibit a charge transfer character in the UV-visible absorption and emission electronic spectra. Furthermore, the calculated reorganization energies, ionization potentials (IPs) and electron affinities (EAs) indicate that the extended C6, C7 and C8 compounds have highest charge-transporting ability among all compounds. It has been found that the D–π–A structure has more influence on the electronic and optoelectronic properties than the D–π–D structure. The hypothesized compound C7 has been found to be a good candidate for application in blue-emitting materials. Therefore, understanding these properties is important to design HTMs with exceptional properties such as stability and high efficiency.