Theoretical study of the tuning role of β-methylthio or β-methylselenyl on the charge-transport properties of acenedithiophenes derivatives.

To date, the manipulation of intermolecular nonconjugation interactions in organic crystals is still a great challenge due to the complexity of weak intermolecular interactions. Here we designed molecules substituted by β-methylselenyl on naphtho[1,2-:5,6-']dithiophene and anthra[2,3-:6,7-']dithiophene, respectively (anti-β-MS-NDT, anti-β-MS-ADT), which together with anti-β-MS-BDT synthesized experimentally all exhibited 2D brickwork π-stacking. Moreover, their maximum molecular carrier mobilities reached 3.

Theoretical investigations on the charge transport properties of anthracene derivatives with aryl substituents at the 2,6-position-thermally stable "herringbone" stacking motifs.

High-performance organic semiconductor materials based on the small aromatic anthracene-core and its derivatives develop comparatively slowly due to the lack of a profound understanding of the influence of chemical modifications on their charge-transfer properties. Herein, the electronic properties and the charge transport characteristics of several typical anthracene-based derivatives with aryl groups substituted at the 2,6-site are systematically investigated by multi-scale simulation methods including Molecular Dynamics (MD) simulation and the full quantum nuclear tunneling model in the framework of density functional theory (DFT). To elucidate the origin of different charge transport properties of these anthracene-based materials, analysis of the molecular stacking and noncovalent intermolecular interaction caused by different substituents was carried out.

Theoretical Investigations into the Electron and Ambipolar Transport Properties of Anthracene-Based Derivatives.

To obtain anthracene-based derivatives with electron transport behavior, two series of anthracene-based derivatives modified by trifluoromethyl groups (-CF) and cyano groups (-CN) at the 9,10-positions of the anthracene core were studied. Their electronic structures and crystal packings were also analyzed and compared. The charge-carrier mobilities were evaluated by quantum nuclear tunneling theory based on the incoherent charge-hopping model.

Crystal Engineering of Biphenylene-Containing Acenes for High-Mobility Organic Semiconductors.

Herein we report the synthesis, crystal structures, and semiconductor properties of new derivatives of bisnaphtho[2',3':3,4]cyclobut[1,2- b:1',2'- i]anthracene (BNCBA). It is found that the π-π stacking of BNCBA in single crystals can be largely modified by alkyl substituting groups of different lengths. In particular, the tetrahexyl derivative exhibits π-π stacking with an unusual zigzag arrangement.

Halogenated Tetraazapentacenes with Electron Mobility as High as 27.8 cm V s in Solution-Processed n-Channel Organic Thin-Film Transistors.

Molecular engineering of tetraazapentacene with different numbers of fluorine and chlorine substituents fine-tunes the frontier molecular orbitals, molecular vibrations, and π-π stacking for n-type organic semiconductors. Among the six halogenated tetraazapentacenes studied herein, the tetrachloro derivative (4Cl-TAP) in solution-processed thin-film transistors exhibits electron mobility of 14.9 ± 4.

Theoretical study on the charge transport in single crystals of TCNQ, F-TCNQ and F-TCNQ.

2,5-Difluoro-7,7,8,8-tetracyanoquinodimethane (F-TCNQ) was recently reported to display excellent electron transport properties in single crystal field-effect transistors (FETs). Its carrier mobility can reach 25 cm V s in devices. However, its counterparts TCNQ and F-TCNQ (tetrafluoro-7,7,8,8-tetracyanoquinodimethane) do not exhibit the same highly efficient behavior.

Theoretical investigations into the charge transfer properties of thiophene α-substituted naphthodithiophene diimides: excellent n-channel and ambipolar organic semiconductors.

A theoretical study was carried out to investigate the electronic structures and the charge transport properties of a series of naphthodithiophene diimide (NDTI) thiophene α-substituted derivatives NDTI-X using density functional theory and classical Marcus charge transfer theory. This study deeply revealed the structure-property relationships by analyzing the intermolecular interactions in crystal structures of C8-NDTI and C8-NDTI-Cl thoroughly by using the Hirshfeld surface, QTAIM theories and symmetry-adapted perturbation theory (SAPT). Our results suggested that a 2-D brick-like π-stacking structure makes C8-NDTI-Cl a more excellent n-type semiconducting material with μ of 2.

Understanding the effects of the number of pyrazines and their positions on charge-transport properties in silylethynylated N-heteropentacenes.

The charge-transport properties of a series of silylethynylated N-heteropentacenes (TIPS-PEN-xN; x = 2, 4) were systematically investigated using Marcus electron-transfer theory coupled with kinetic Monte Carlo simulations. Electronic structure calculations showed that introducing more pyrazine rings decreases the energy levels of the lowest unoccupied molecular orbitals (LUMOs) and should aid electron transfer. The number and the positions of the pyrazine rings greatly influence the molecular packing in crystals and hence the intermolecular electronic coupling.

Are triphenylamine-functionalized or carbazole-functionalized iridium complexes the more effective phosphorescent materials? A theoretical perspective.

The ground and excited states, charge injection/transport, and phosphorescence properties of eleven carbazole- and triphenylamine-functionalized Ir(III) complexes were investigated by using the DFT method. By analyzing the spin-orbit coupling (SOC) matrix elements, radiative decay rate constants k(r), and the electronic structures and energies at the S₀(opt) and T₁(opt) states, it was possible to rationalize the order of the experimental phosphorescence quantum yields of a series of Ir(III) complexes and to predict that [Ir(Nph-2-Cz-tz)3] has a higher phosphorescence quantum yield than [Ir(TPA-tz)3] (TPA=triphenylamine, tz=thiazolyl, Cz=carbazole, Nph=N-phenyl). Carbazole-functionalized Ir(III) complexes were shown to be efficient phosphorescent materials that have not only fast but also balanced electron/hole-transport performance as well as high phosphorescence quantum yields.

How dual bridging atoms tune structural and optoelectronic properties of ladder-type heterotetracenes?--a theoretical study.

Ladder-type heterotetracenes possessing fully ring-fused structures are a promising class of optoelectronic materials in terms of the lack of any conformational disorder, intense emission and high carrier mobility. To uncover how dual bridging atoms tune their structural and optoelectronic properties, the heterotetracenes were systematically investigated by theoretical calculations from several aspects, such as (i) the geometrical structures of ground and excited states; (ii) the highest occupied molecular orbitals (HOMO), the lowest unoccupied molecular orbitals (LUMO); (iii) ionization potentials (IP), electron affinities (EA), hole extraction potentials (HEP), electron extraction potentials (EEP), internal reorganization energies (λ(int)) and transfer integrals (V); (iv) the absorption and emission spectra in vacuum and the dichloromethane (CH(2)Cl(2)) solvent, band gaps (E(g)), excitation energies at the lowest singlet (E(S1)) or triplet (E(T1)) states as well as radiative lifetimes (τ). The theoretical investigations may be useful for finding new leading materials and are likely to provide important information for improving their photoelectric performance.