Fine-Tuning of Crystal Packing and Charge Transport Properties of BDOPV Derivatives through Fluorine Substitution

Abstract

Molecular packing in organic single crystals greatly influences their charge transport properties but can hardly be predicted and designed because of the complex intermolecular interactions. In this work, we have realized systematic fine-tuning of the single-crystal molecular packing of five benzodifurandione-based oligo(p-phenylenevinylene) (BDOPV)-based small molecules through incorporation of electronegative fluorine atoms on the BDOPV backbone. While these molecules all exhibit similar column stacking configurations in their single crystals, the intermolecular displacements and distances can be substantially modified by tuning of the amounts and/or the positions of the substituent fluorine atoms. Density functional theory calculations showed that the subtle differences in charge distribution or electrostatic potential induced by different fluorine substitutions play an important role in regulating the molecular packing of the BDOPV compounds. Consequently, the electronic couplings for electron transfer can vary from 71 meV in a slipped stack to 201 meV in a nearly cofacial antiparallel stack, leading to an increase in the electron mobility of the BDOPV derivatives from 2.6 to 12.6 cm(2) V(-1) s(-1). The electron mobility of the five molecules did not show a good correlation with the LUMO levels, indicating that the distinct difference in charge transport properties is a result of the molecular packing. Our work not only provides a series of high-electron-mobility organic semiconductors but also demonstrates that fluorination is an effective approach for fine-tuning of single-crystal packing modes beyond simply lowering the molecular energy levels.

Side‐Chain Impact on Molecular Orientation of Organic Semiconductor Acceptors: High Performance Nonfullerene Polymer Solar Cells with Thick Active Layer over 400 nm

“…[14,[17][18][19][20][21][22][23][24][25][26][27][28][29] And the n-OS acceptors-based devices have achieved power conversion efficiency (PCE) as high as over 12%. [43][44][45][46][47] Up to now, great efforts have been devoted to development of building blocks, terminal functional groups and side chains, which can effectively tune the band gap and energy levels of the n-OS acceptors. [43][44][45][46][47] Up to now, great efforts have been devoted to development of building blocks, terminal functional groups and side chains, which can effectively tune the band gap and energy levels of the n-OS acceptors.…”

Trends in molecular design strategies for ambient stable n-channel organic field effect transistors

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Anion-controlled dimer distance induced unique solid-state fluorescence of cyano substituted styrene pyridinium

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