Two main factors governing the effect of terminal substituents on the properties of thiophene–phenylene co-oligomers are revealed.

Organic electronics requires materials with high charge mobility. Despite decades of intensive research, charge transport in high-mobility organic semiconductors has not been well understood. In this Letter, we address the physical mechanism underlying the exceptionally high band-like electron mobility in F-TCNQ (2,5-difluoro-7,7,8,8-tetracyanoquinodimethane) single crystals among a crystal family of similar compounds F-TCNQ (n = 0, 2, 4) using a combined experimental and theoretical approach. While electron transfer integrals and reorganization energies did not show outstanding features for F-TCNQ, Raman spectroscopy and solid-state DFT indicated that the frequency of the lowest vibrational mode is nearly twice higher in the F-TCNQ crystal than in TCNQ and F-TCNQ. This phenomenon is explained by the specific packing motif of F-TCNQ with only one molecule per primitive cell so that electron-phonon interaction decreases and the electron mobility increases. We anticipate that our findings will encourage investigators for the search and design of organic semiconductors with one molecule per primitive cell and/or the poor low-frequency vibrational spectrum.

ones; only a few OSs show reproducible mobilities exceeding that for amorphous silicon (μ ≈ 1 cm 2 V −1 s −1 ), a workhorse of modern thin-film electronics. [1,2] Moreover, reliable mobility measurements in OSs are difficult and time-consuming. For example, the commonly used measurement method with the use of organic field-effect transistors (OFETs) is complicated by many factors, such as the contacts, the architecture, the dielectric, etc., which results in various artifacts and pitfalls. [3] Therefore, focused search for high-mobility OS materials among a huge number of candidates needs an effective approach to charge-carrier mobility estimation prior to its measurements in devices. Importantly, in the context of such a search, one does not necessarily have to predict a value of μ closely enough to the experimental mobility to be further measured: a mobility estimation characterized with a good correlation with experimental μ values for quite a lot of (but not all) OSs also provides a way toward efficient screening of high-mobility OS materials.Two types of OSs show high charge-carrier mobilities: smallmolecule organic crystals (crystalline OSs) and polymers. In what follows, we will focus on crystalline OSs, whose crystal structures resolved from X-ray diffraction data are needed for Further progress in organic electronics demands new highly efficient organic semiconductor (OS) materials. So far, however, band-like charge transport with high mobilities has been reliably demonstrated only in a few OSs, and development of efficient methods for search of high-mobility materials among a plethora of OSs remains extremely important. In the present work, a spectroscopic method is presented for screening of crystalline OSs with efficient charge transport, to be used prior to time-consuming device measurements. Specifically, the work focuses on a physical rationale and an experimental benchmark of a correlation between the intensities of the low-frequency Raman spectrum and the strength of dynamic disorder limiting the charge-carrier mobility in a material. As a result, two physicsinspired spectroscopic descriptors for charge-carrier mobility estimation are suggested, both of which clearly correlate with device mobilities reported for various crystalline OSs. It is anticipated that the spectroscopic method based on these descriptors can serve as a powerful search tool for revealing new high-mobility OS materials.

Properties of the organic semiconductors can be finely tuned via changes in their molecular structure.