Impact of Edge-Core Structures and Substituent Effects on the Electronic and Charge-Transport Properties of Heteroaromatic Ring-Fused Oligomers

Abstract

Herein, we systematically studied the electronic and conducting properties of the thiophene-fused polycyclic aromatic compounds and their analogues and discussed in detail the influences of edge-core structure, heteroatom substitution, and functionalization on their field-effect transistor properties and solid-state packing motifs. It was found that the influence of edge-core structure and heteroatom substitution on the electronic properties and reorganization energies of semiconducting materials mainly originates from the variations of the frontier molecular orbital charge distributions and the steric hindrance as well as the conjugate degree of compounds. Moreover, our results also showed that the fusion of benzene rings at the longitudinal end could effectively decrease energy barrier of charge injection and reorganization energies and change the molecular arrangement from herringbone packing to π stacking, which provides a promising way to functionalize organic semiconducting molecules.

Design, synthesis, chemical stability, packing, cyclic voltammetry, ionisation potential, and charge transport of [1]benzothieno[3,2-b][1]benzothiophene derivatives

“…In order to probe whether the lower hole mobility measured for 2a has an intrinsic origin or is only due to a less uniform packing, as suggested by POM images, the hole transport properties of 1a and 2a have been investigated at the theoretical level, considering in the first approximation a hopping transport regime (see Experimental section). The internal reorganization energies associated to positive polarons are larger for 2a (360 meV and 245 meV for 2a and 1a, respectively, in agreement with earlier studies) 71,72 and hence detrimental for hole transport. This evolution is consistent with a previous work pointing to a systematic increase in the reorganization energies of discotic conjugated compounds upon introduction of oxygen atoms between the conjugated core and alkyl chains.…”

A DFT Study on the Electronic Structures and Conducting Properties of Rubrene and its Derivatives in Organic Field-Effect Transistors

“…Further analysis indicates that the low-frequency vibration modes contributing most to λ h and λ e values, such as 21 cm −1 , 338 cm −1 in neutral molecule and 26 cm −1 , 336 cm −1 in charged molecule, corresponds torsion vibration between four phenyl rings and naphthacene core; and the high-frequency vibration modes contributing most to λ h and λ e values, such as 1335 cm −1 , 1579 cm −1 in neutral molecule and 1332 cm −1 , 1574/1585 cm −1 in charged molecule, corresponds stretching vibration of chemical bonds in the naphthacene core. Thus, we can conclude that the bending vibration induced by variation of bond angles contributes more to the electron-transfer reorganization energy than the hole-transfer reorganization energy, as is similar with diphenyl-naphtho[2,3-b:6,7-b′]dithiophenematerial studied before 17 .

Figure 2( a ) Frequency dependence of reorganization energies for neutral and anionic rubrene upon electron-transfer process (top) and for neutral and cationic rubrene upon hole-transfer process (below); ( b ) Frequency dependence of reorganization energies for neutral and anionic fm-rubrene upon electron-transfer process (top) and for neutral and cationic fm-rubrene upon hole-transfer process (below); the black lines represent neutral compounds, the red lines represent anionic compounds, and the blue lines represent cationic compounds.

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Molecular Semiconductors for Logic Operations: Dead‐End or Bright Future?

“…The importance of the isotropy of charge transport within the x,y conduction plane has somewhat been overlooked. Nowadays, it is increasingly recognized as an important design element for high µ semiconductors . How to judge the isotropy of charge transport?…”