Fused Thiophene Semiconductors: Crystal Structure–Film Microstructure Transistor Performance Correlations

Abstract

The molecular packing motifs within crystalline domains should be a key determinant of charge transport in thin-fi lm transistors (TFTs) based on small organic molecules. Despite this implied importance, detailed information about molecular organization in polycrystalline thin fi lms is not available for the vast majority of molecular organic semiconductors. Considering the potential of fused thiophenes as environmentally stable, highperformance semiconductors, it is therefore of interest to investigate their thin fi lm microstructures in relation to the single crystal molecular packing and OTFT performance. have been scrutinized, such assumptions have been proven to sometimes be inaccurate, and it is now known that molecular packing in thin fi lms may differ signifi cantly from that in the bulk crystal structures, especially near the dielectric interface. For example, in thin fi lm form, both tetraceno[2,3-b]thiophene [ 17 ] and pentacene [ 16 ] exhibit a local molecular packing distinctly different from that in the bulk crystal. These observations highlight the necessity of obtaining microstructural details for thin organic fi lms.In this contribution, the molecular packing motifs of fi ve newly synthesized BTDT [ 9 ] derivatives ( Scheme 2 ), are studied both in bulk single crystals and in thin fi lms by single crystal diffraction and grazing incidence wide angle X-ray scattering (GIWAXS). We fi rst introduce the new BTDT molecules and describe their thermal, optical, and electrochemical properties. We then compare the bulk and thin fi lm structures by analyzing single-crystal X-ray diffraction and GIWAXS data. Lastly, the effect of thin fi lm microstructure on TFT performance is discussed. The results indicate that these BTDT derivatives have different molecular packing in thin fi lms versus the bulk crystals. In the case of P-BTDT , Bp-BTDT , Np-BTDT , and BBTDT , it will be seen that two types of lattices coexist, and that these are slightly strained compared to their bulk crystal forms. In contrast, for PF-BTDT fi lms, a single lattice is observed, however, this lattice has no apparent correspondence to the bulk crystal form. For P-BTDT , which yields the best performing TFTs of the series, the dominance of the more strained lattice relative to the bulk-like lattice may explain the excellent charge transport properties. On the other hand, poor crystallinity and poor surface coverage at the substrate interface explains the poor device performance of PF-BTDT fi lms. Results SynthesisDetails of the various BTDT syntheses can be found in the Supporting Information or previous literature. [ 9 ] Briefl y, the derivatives [ 2 , 9-14 ] offer a potential solution to this challenge, owing to their combination of suffi ciently high-lying excited states and high ionization potentials to suppress photo-oxidation, [ 11 ] and bulk single crystal packing motifs which are very similar to that of pentacene. Among organic semiconductor materials for p-channel devices, several fused thiophene derivatives with increased numb...

Diperfluorophenyl Fused Thiophene Semiconductors for n‐Type Organic Thin Film Transistors (OTFTs)

“…The samples investigated by GIWAXS were those that exhibited the best TFT performance (vide infra), which were those with the semiconductor deposited on OTS‐functionalized substrates and at an optimal deposition temperature of 25 or 110 °C. Our previous report established that thin film organic semiconductors of this general type crystallize with lattice parameters that are similar to, but not identical to, the lattice parameters of the corresponding bulk single crystals. This observation is again made here.…”

“…The perfluorinated TTA derivatives DFP‐TTA and DFPT‐TTA crystallize in the monoclinic space group P‐2 1 /c ( Table 2 ). Similar to other fused thiophenes, the unit cell of DFP‐TTA exhibits a commonly observed herringbone packing motif (Figure S1, Supporting Information) . The fluorinated phenyl moiety is slightly twisted with respect to the fused thiophene core, with a dihedral angle of 10.2° (Figure S1B, Supporting Information, Table 3 ).…”

“…The growing interest in high‐performance, air‐stable organic semiconductors has benefited greatly from the development of fused thiophene derivatives as a viable alternative to acene‐based small molecule materials . Among several fused thiophene derivatives reported, there have been a few quinoidal n‐channel fused thiophenes . Although devices based on quinoidal n‐channel fused thiophene derivatives showed relatively high electrical performance, there have been a few limitations: i) synthesis of these materials is challenging, ii) large amounts of (expensive) Pd catalyst (e.g., 0.3–1.0 eq.)…”

A Highly Planar Nonfullerene Acceptor with Multiple Noncovalent Conformational Locks for Efficient Organic Solar Cells

“…One efficient strategy of rigidifying the molecular backbone is to connect the adjacent conjugated moieties with additional covalent bonds to form ladder‐type structures . However, this method usually requires multiple‐step syntheses, which could be costly and labor intensive.…”

Efficient Synthesis and Properties of [1]Benzothieno[3,2‐b]thieno[2,3‐d]furans and [1]Benzothieno[3,2‐b]thieno[2,3‐d]thiophenes

“…[2] Bisbenzo [d,d′]thieno [3,2-b:4′,5′-b′]dithiophenes) (BBTDT) containing thiophene ring-fused thieno [3,2-b]thiophene (DTT; dithieno [3,2-b:2′,3′-d]thiophenes) also exhibited hole mobility ( = 0.15 cm 2 V -1 s -1 ) (Figure 1a). [3] Meanwhile, π-conjugated molecules containing thieno [3,2b]furan are known to be both organic semiconductor materials and bioactive compounds. For example, bisbenzo [d,d′]furo [2,3d;2′,3′-d′]benzo [1,2-b;4,5-b′]dithiophene (BFBDT) exhibited hole mobility (0.04 cm 2 V -1 s -1 ) and 3-amino[1]benzothieno [3,2b]furan-2-carboxyamide potently inhibited IKK (Figure 1b).…”