Crystal alignment of surface stabilized polymorph in thioindigo films

Abstract

Thioindigo (2-(3-Oxo-1-benzothiophen-2(3H)-ylidene)-1-benzothiophen-3(2H)-one) is a synthetic dye related to the natural compound Indigo. Notwithstanding the interest aroused recently by its employment as a functional material in a number of applications, a satisfactory characterization of its solid state is still missing. In this work, we study the occurrence of the two thioindigo α and β polymorphs under various growth conditions, and find that their structural similarity implies they often coexist. However, whereas polymorph β is certainly predominant in the bulk phase, polymorph α grows preferentially on substrates, turning out to be the surface stabilized phase in highly homogeneous and ordered films obtained by the bar-assisted meniscus shearing method (BAMS). DFT calculations support the experimental findings, aiding in the polymorph spectroscopic identification and to the interpretation of the order in the films of polymorph α.

Thorough investigation on the high-temperature polymorphism of dipentyl-perylenediimide: thermal expansion vs polymorphic transition.

“…Further increase of the temperature soften and broaden the spectral features. The lattice phonons are known to be really sensitive even to slight change in crystal packing, [46][47][48] but in this case we observe very similar patterns for all the polymorphs. This could not be surprising for form I and form II which have the same structure with a small difference in the later alkyl chain configuration, instead it is really unexpected the similarity with form III which has a triclinic structure with 3 molecules per unit cell.…”

Selection of the two enantiotropic polymorphs of diF-TES-ADT in solution sheared thin film transistors

“…10 One of the most recently explored technique used to deposit soluble OSCs for OFET fabrication is solution shearing, which has been explored employing bare OSCs and OSCs blended with binding polymers. [11][12][13][14][15][16] This family of techniques has been proved to result in homogenous and highly crystalline thin films exhibiting an enhanced electrical performance.…”

Bulk and Surface‐Mediated Polymorphs of Bio‐Inspired Dyes Organic Semiconductors: The Role of Lattice Phonons in their Investigation

“…The surface of engineered substrates may act as a template in molecular deposition [75] and the subtle interplay of interactions at the interface may result into altogether new molecular arrangements, which are not observed in the bulk. [76][77][78][79] When the interface has the effect of stabilizing forms that would otherwise be metastable under the adopted experimental conditions, the definition "surface stabilized" appears adequate. [80,81] Finally, some thin film phases can be better described as structures which are in fact still related to a parent bulk structure, but perturbed with respect to this as a result of the substrate influence on the growth of the first monolayers.…”