Carbazole endcapped heterofluorenes as host materials: theoretical study of their structural, electronic, and optical properties

Abstract

By mimicking the molecular structure of 4,4'-bis(N-carbazolyl)-2,2'-biphenyl (CBP), which is a widely used host material, a new series of host molecules (carbazole-endcapped heterofluorenes, CzHFs) were designed by linking the hole-transporting carbazole to the core heterofluorene molecules in either meta or para positions of the heterofluorene. The aromatic cores considered in this study are biphenyl, fluorene, silafluorenes, germafluorenes, carbazole, phosphafluorene, oxygafluorene, and sulfurafluorene. To reveal their molecular structures, optoelectronic properties and structure-property relationships of the proposed host materials, an in-depth theoretical investigation was elaborated via quantum chemical calculations. The electronic structures in the ground states, cationic and anionic states, and lowest triplet states of these designed molecules have been studied with emphasis on the highest occupied molecular orbitals (HOMOs), the lowest unoccupied molecular orbitals (LUMOs), energy gaps (E(g)), triplet energy gaps ((3)E(g)), as well as some other electronic properties including ionization potentials (IPs), electron affinities (EAs), reorganization energies (λ), triplet exciton generation fraction (χ(T)), spin density distributions (SD), and absorption spectra. These photoelectronic properties can be tuned by chemical modifications of the heteroatom and the carbazole substitution at different positions. This study provides theoretical insights into the nature of host molecules, and shows that the designed CzHFs can meet the requirements of the host materials for triplet emitters.

Theoretical study on optoelectronic properties of fluorene derivatives with pyrene-functional groups: effect of the heteroatoms and pyrene’ substituting position

“…On the basis of the above calculations, the corresponding IPs, EAs, HEPs, EEPs, and s were obtained. Because some investigations have shown that the B3LYP functional usually underestimate the excitation energy [13,14,17] while the M06-2X functional can obtain better results [18] in this work the absorption spectra of these compounds were predicted by two methods in vacuum: TD B3LYP/6-31G(d) and TD M06-2X/6-31G(d).…”

“…[13][14][15][16]. In this work, the geometric structures of the ground states including neutral and ionized states of all the studied compounds were optimized using the B3LYP/ 6-31G(d) method.…”

“…So small and balanceable hole and electron reorganization energies should result in efficient charge transport. The reorganization energy, describing the strength of the electron-phonon (vibration) coupling in charge transfer process, is obtained directly from the adiabatic potential-energy surfaces of neutral/cation or neutral/ anion species in the work [13,14]. for holes can be defined as follows:…”

A DFT and TDDFT investigation of interactions between 1-hydroxypyrene and aromatic amino acids

“…It is known that B3LYP may fail to produce excitation properties [59][60][61][62][63]; therefore, TDDFT calculations have been repeated using CAM-B3LYP, a specific version of B3LYP designed for excitedstate calculations [55]. To assess the solvent effect, TDDFT/ B3LYP/6-311++G(d,p) and TDDFT/CAM-B3LYP/6-311++G(d,p) calculations coupled with the Polarizable Continuum Model (PCM) have been performed in water with a dielectric constant of 78.4.…”

Heteroatom-Bridged Benzothiazolyls for Organic Solar Cells: A Theoretical Study

“…According to the studies of heterofluorenes [28][29][30][31][32] , many other heteroatoms with characteristic electronic properties can be also adopted. In addition, the specific interactions between the bridging heteroatom and the π-conjugated organic framework may induce novel electronic states with significantly modified optoelectronic properties for various device applications 33 .…”