Theoretical Studies of the Structural, Electronic, and Optical Properties of Phosphafluorenes

Abstract

Phosphafluorenes have drawn increasing attention recently in the applications of organic electronic devices due to their particular optoelectronic properties. To reveal their molecular structures, optoelectronic properties, and structure-property relationships of the newly emerged functional materials, an in-depth theoretical investigation was elaborated via quantum chemical calculations. The optimized geometric and electronic structures in both ground and exited states, the mobility of the hole and electron, the absorption and emission spectra, and the singlet exciton generation fraction of these novel phosphors-containing materials have been studied by density functional theory (DFT), single excitation configuration interaction (CIS), time-dependent density functional theory (TDDFT) methods, and the polarizable continuum model (PCM). The results show that the highest occupied molecular orbitals (HOMOs), the lowest unoccupied molecular orbitals (LUMOs), triplet energies ((3)E(g)), energy gaps (E(g)), as well as some other electronic properties including ionization potentials (IPs), electron affinities (EAs), reorganization energies (lambda), the singlet exciton generation fraction, radiative lifetime, and absorption and emission spectra can be easily tuned by chemical modifications of the phosphorus atom via methyl, phenyl, oxygen, sulfur, or selenium substitution, indicating that the phosphafluorenes are interesting optoelectronic functional materials, which have great potential in the applications of OLEDs, organic solar cells, organic storage, and sensors.

Conjugated Asymmetric Donor‐Substituted 1,3,5‐Triazines: New Host Materials for Blue Phosphorescent Organic Light‐Emitting Diodes

“…In the solid state, the PL spectra of ADTs are blueshifted up to 63 nm in comparison with that in solution, probably due to the better stabilizing effects of the solvent on the base state (S 0 ) than the excited state (S 1 ) of the D-A structure of ADTs. [26] The strongest PL peaks of ThDCzT, PhDCzT, DThCzT, and DPhCzT in solid film are significantly redshifted with low photoluminescent efficiency (< 10 %) in comparison with that of NPhDCzT and DNPhCzT. The low quantum efficiency is probably due to the intermolecular aggregation because of the planar architectures as revealed by the DFT-optimized structures.…”

“…[7d, 26,31] Device fabrication and measurement: In a general procedure, ITOcoated glass substrates were etched, patterned, and washed with detergent, deionized water, acetone, and ethanol in turn. Organic layers were deposited by high-vacuum ( % 4 10 À4 Pa) thermal evaporation with a rate of 0.1-0.2 nm s À1 .…”

Theoretical study of the electronic ground states and low-lying singlet excited states of thiophene-based spirofluorenes

“…The vertical transition energies were calculated on the basis of the AM1 optimized geometries (ground state geometry for the calculation of the absorption energy and lowest-excited state geometry for the emission energy), using Zerner's intermediate neglect differential overlap for spectroscopy (ZINDO/S) [9] method with singly excited configuration interaction (CI) on the basis of the 20 upper occupied and 20 lower unoccupied MOs. In the calculation of absorption wavelength of the corresponding non-spirofluorenes, the singly excited configurations were generated on the basis of the 10 upper occupied and 10 lower unoccupied MOs in order to maintain size consistency between spiro and non-spiro molecules [10].…”

λ5‐Phospha[7]helicenes: Synthesis, Properties, and Columnar Aggregation with One‐Way Chirality

“…Such large Stokes shift are common for phosphole-containing compounds and suggest a large rearrangement of the pconjugated framework upon photoexcitation. [17] The quantum yield of 1 in solution is 7.8 %, whereas the quantum yield in the solid state is much lower (0.1 %). In contrast, 2 has a low quantum yield of 0.1 % both in solution and in the solid state.…”