Star‐Shaped Oligothiophenes for Solution‐Processible Organic Field‐Effect Transistors

Abstract

We have designed and successfully synthesized star‐shaped oligothiophenes, which could be used as semiconducting materials for solution‐processible organic field‐effect transistors (FETs). By systematically changing the chemical structure of the star‐shaped oligothiophenes we obtained the structural requirements needed for making working FETs from them. UV‐vis fluorescence measurements showed that a molecule of the star‐shaped compounds under consideration is not a fully conjugated molecule, but it has three independently conjugated oligothienyl‐phenylene blocks. A possible scheme of molecular packing of the star‐shaped oligothiophenes in a lamellar structure was proposed and confirmed by atomic force microscopy (AFM) and X‐ray diffraction (XRD) measurements. Although the star‐shaped semiconductors show a somewhat lower mobility than their linear analogs, they possess better solubility and film‐forming properties, leading to improved spin‐coating processing. The best FETs were made by spin‐coating 1,3,5‐tris(5″‐decyl‐2,2′:5′,2″‐terthien‐5‐yl)benzene from a chloroform solution, which resulted in a mobility of 2 × 10–4 cm2 V –1s–1, a 102 on/off ratio at gate voltages of 0 V and –20 V, and a threshold voltage close to 0 V.

Conjugated Thiophene Dendrimer with an Electron-Withdrawing Core and Electron-Rich Dendrons: How the Molecular Structure Affects the Morphology and Performance of Dendrimer:Fullerene Photovoltaic Devices

“…Also the d-spacing suggests 2 has an edge-on alignment similar to what has been seen in other small molecules. 24 Figure 3a also shows XRD results from dendrimer:PCBM (1:4) bulk heterojunction films at low scattering angles. No ordering is seen in the blend of 1:PCBM, but a small peak is still seen in 2:PCBM at 2.4°, indicating that partial dendrimer ordering is retained despite the heavy PCBM loading.…”

From One‐ to Three‐Dimensional Organic Semiconductors: In Search of the Organic Silicon?

“…Compound 7 led to a hole mobility of 2 × 10 -4 cm 2 V -1 s -1 with an on/off ratio of 100. [30] Star-shaped compounds were found to exhibit better solubility and film-forming properties than their linear counterparts. Decreasing the length of the nT chain to two units (6) or replacing a thiophene ring by a phenyl one (8) induced a dramatic decrease of mobility.…”

“…Decreasing the length of the nT chain to two units (6) or replacing a thiophene ring by a phenyl one (8) induced a dramatic decrease of mobility. [30] Sun et al have used star-shaped oligothiophene-functionalized truxene (9-11) for OFET fabrication. [31] The devices were made on a highly doped silicon substrate with a 400 nm SiO 2 layer as dielectric.…”

“…2D conjugated molecules with short-chain nTs attached on a central benzenic core have been synthesized by several groups. [29][30][31][32][33][34][35] Kirchmeyer and co-workers have synthesized solution-processable star-shaped oligothiophenes 6-8 in which the conjugated chains are directly attached at the benzene core. [30] OFETs were realized by spin-coating chloroform solutions onto n ++ -doped silicon substrate.…”

An iterative strategy for the synthesis of oligothiophenes by catalytic cross‐coupling reactions

“…In addition, oligothiophenes themselves exhibit intrinsic physical properties due to their well-defined structure and their large conjugation length. These effects led to the development of thiophene-based electronic devices such as electroluminescent diodes [5] or field-effect transistors [6]. On the other hand, the Correspondence to: Frédéric Chérioux; e-mail: frederic.cherioux@unine.ch.…”