Synthesis, Structural Characterization, and Unusual Field-Effect Behavior of Organic Transistor Semiconductor Oligomers: Inferiority of Oxadiazole Compared with Other Electron-Withdrawing Subunits

Abstract

A new series of heterocyclic oligomers based on the 1,3,4-oxadiazole ring were synthesized. Other electron-deficient cores (fluorenone and fumaronitrile) were introduced to investigate the oligomers as n-channel materials. The physical properties, thin film morphologies, and field-effect transistor characteristics of the oligomers were evaluated. Thin films were deposited at different substrate temperatures and on variously coated Si/SiO(2) for device optimization. Contrary to our expectations, the thin film devices of 4 revealed p-channel behavior, and the average hole mobility was 0.14 cm(2) V(-1) s(-1) (maximum value 0.18 cm(2) V(-1) s(-1)). Compound 11 is the first example of an oxadiazole-containing organic semiconductor (OSC) oligomer in an n-channel organic field-effect transistor (OFET) and shows moderate mobilities. Non-oxadiazole-containing oligomers 9 and 12 showed n-channel OFET behavior on hexamethyldisilazane-treated and Cytop spin-coated SiO(2) in vacuum. These are the first fluorenone- and fumaronitrile-based n-OSCs demonstrated in transistors. However, oxadiazole-core materials 14 and 16 were inactive in transistor devices.

Synthesis of new, highly luminescent bis(2,2’-bithiophen-5-yl) substituted 1,3,4-oxadiazole, 1,3,4-thiadiazole and 1,2,4-triazole

“…Transition metal-catalysed cross-coupling reactions, such as Stille, Suzuki etc. are typically used for the formation of thiophene–thiophene or azole–thiophene bonds [14,16–17]. However, the best results (higher yields, more facile purification, shorter reaction times) are obtained by the formation of the azole ring via appropriately functionalized bithiophenes [14,22].…”

“…One of the possible ways of the preparation of low molecular mass semiconductors, showing higher than oligothiophene IP values, is to synthesize molecules in which a central electron accepting group separates two bi-, ter- or quaterthiophene units. Such compounds containing thiadiazole [10–15], oxadiazole [14–17] or tetrazine units [13,18–20] have been reported. Moreover, luminescence properties of these derivatives are superior to those of the corresponding penta-ring oligothiophenes.…”

Visible‐Light‐Triggered Molecular Photoswitch Based on Reversible E/Z Isomerization of a 1,2‐Dicyanoethene Derivative

“…[19] Keywords: 1,2-dicyanoethene ·diarylethenes · molecular switches ·p hotochromism ·photoisomerization Its two isomers exhibit significantly different molecular geometries leading to highly contrasting coplanarities, effective conjugations,molecular dipole moments,end-to-end distances,a nd symmetries.S pectral studies on pure isomers showed al arge separation between their l max and avariation in their relative absorption strengths.A sar esult, 4TCE can be efficiently switched between its cis and trans forms by irradiating with blue and white light, such that it is au seful photoswitch with manageable photoisomerization, high con- Angewandte version efficiency, and no requirement of aU Vl ight trigger.…”

The synthesis and optical properties of novel triphenylamine containing 1,3,4-oxadiazole derivatives

“…The 1,3,4-oxadiazole derivatives have been widely studied as materials in electroluminescent (EL) devices due to their electron deficiency, high thermal and oxidative stability [6][7][8][9][10][11]. Furthermore, oxadiazole-based oligomers with electron-accepting end moieties have also been applied in organic field-effect transistors (OFETs) [12,13]. In recent years, many 1,3,4-oxadiazole derivatives have been widely used as electrontransporting materials.…”