Multiscale Self-Organization of the Organic Semiconductor α-Quinquethiophene

Abstract

We show that thin films grown by vacuum sublimation, or formed by melted powders, of semiconductor alpha-quinquethiophene (T5) exhibit a hierarchical self-affinity organization that spans scales from tens of nanometers to hundreds of micrometers. T5 organization was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), and optical microscopy. XRD showed that vacuum-evaporated T5 films were characterized by a preferred orientation of the h00 planes parallel to the glass substrate. Melting of the films followed by rapid quenching to room temperature led to the formation of micrometer-sized, single-crystal-like structures, characterized by uniaxially aligned stripes. XRD proved that the melting-quenching process enhanced molecular ordering and increased the size of domains with the molecule's long axes tilted by about 65 degrees with respect to the substrate plane and piled up side-by-side along parallel columns. AFM measurements on the melt-quenched structures showed that a hierarchical architecture was built by reiteration across multiple length scales of the same recurring motif. Because of the tendency of T5 to form highly crystalline vacuum-evaporated thin films, a field-effect hole mobility comparable to state-of-the-art FET mobility of alpha-sexithiophene films was reached, without any attempt to optimize deposition conditions.

The Versatile Thiophene: An Overview of Recent Research on Thiophene‐Based Materials

“…2). [41] This behavior is peculiarly different from that of the lower and higher homologues of the series, quaterthiophene (T4) and sexithiophene (T6), and undoubtedly has some relation to the different symmetry of oligomers with odd and even numbers of thiophene rings. Owing to its peculiar self-assembly properties, T5 forms very crystalline vacuum-evaporated thin films with high FET charge mobilities.…”

“…Owing to its peculiar self-assembly properties, T5 forms very crystalline vacuum-evaporated thin films with high FET charge mobilities. [41] However, minor structural modifications cause a drop in FET charge mobility by several orders of magnitude, even when the modified systems are able to self-organize in highly crystalline thin films. [42] Recently, we have also found that the electroluminescence properties of thiophene oligomers may be deeply affected by their self-assembly modalities.…”

Tuning Optoelectronic Properties of Ambipolar Organic Light‐ Emitting Transistors Using a Bulk‐Heterojunction Approach

“…The results presented show that the bulk-heterojunction approach, which is widely used in organic photovoltaic cells, can be successfully employed to select and tailor the functionality of field-effect devices, including ambipolar charge transport and light emission. porting material, [35] and P13 belongs to a class of perylene derivatives, which are well-studied electron-transporting materials. [36] The molecular structures of T5 and P13 and a schematic of the device architecture are shown in Figure 1.…”

Ambipolar light-emitting organic field-effect transistor

“…The two materials have been selected because of their transport and luminescence properties. ␣-5T is known as holetransporting material, 20 and from pure reference devices we extracted a hole mobility of 2.5ϫ 10 −2 cm 2 / V s. P13 belongs to a class of perylene derivatives, which are well-studied electron-transporting materials. The pure reference device had an electron mobility of 5 ϫ 10 −3 cm 2 / V s. The electron and hole mobilities of the pure materials lie within one order of magnitude, which is a prerequisite for achieving ambipolar current characteristics in a coevaporated film.…”