Tuning of Molecular Electrostatic Potential Enables Efficient Charge Transport in Crystalline Azaacenes: A Computational Study

Abstract

The chemical versatility of organic semiconductors provides nearly unlimited opportunities for tuning their electronic properties. However, despite decades of research, the relationship between molecular structure, molecular packing and charge mobility in these materials remains poorly understood. This reduces the search for high-mobility organic semiconductors to the inefficient trial-and-error approach. For clarifying the abovementioned relationship, investigations of the effect of small changes in the chemical structure on organic semiconductor properties are particularly important. In this study, we computationally address the impact of the substitution of C-H atom pairs by nitrogen atoms (N-substitution) on the molecular properties, molecular packing and charge mobility of crystalline oligoacenes. We observe that besides decreasing frontier molecular orbital levels, N-substitution dramatically alters molecular electrostatic potential, yielding pronounced electron-rich and electron-deficient areas. These changes in the molecular electrostatic potential strengthen face-to-face and edge-to-edge interactions in the corresponding crystals and result in the crossover from the herringbone packing motif to π-stacking. When the electron-rich and electron-deficient areas are large, sharply defined and, probably, have a certain symmetry, calculated charge mobility increases up to 3–4 cm2V−1s−1. The results obtained highlight the potential of azaacenes for application in organic electronic devices and are expected to facilitate the rational design of organic semiconductors for the steady improvement of organic electronics.

Non‐Local Electron‐Phonon Interaction in Naphthalene Diimide Derivatives, its Experimental Probe and Impact on Charge‐Carrier Mobility

“…[1,47,48] Thus, the exciton-phonon interaction is related to modulation of electron/hole energies (i.e., local electron-phonon interaction) and J (i.e., NLEPI). This relation is corroborated by the fact that the calculated contributions of various vibrational modes to the local electron-phonon interaction [27,49,50] are in reasonable correlation with the Raman intensities. Moreover, contributions of the lowest-frequency Raman mode to the NLEPI along different charge transfer directions revealed a correlation with the experimental anisotropy of its Raman intensity in TCNQ crystal.…”

Utilization of the through-space effect to design donor–acceptor systems of pyrrole, indole, isoindole, azulene and aniline

“…The electrostatic complementarity observed in these core-expanded systems holds significant potential for the construction of charge transfer complexes, offering promising applications. 109…”

Charge Transport in Organic Semiconducting Crystals Exhibiting TADF: Insight from Quantum-Chemical Calculations

“…1) that introduces attractive electrostatic interactions between parallel conjugated cores, in line with Refs. [35][36][37][38]. However, in most of the crystals studied donor (acceptor) moieties tend to dimerize, forming tightly bound pairs which weakly couple to each other.…”