Thiophene-based materials are some of the most versatile conjugated materials due to their combination of environmental stability and ease of synthetic modification. They are widely employed for photoelectronic applications, such as Organic Photovoltaics, however, thiophene-based materials in emissive applications fall far behind, possibly because of the limited fluorescent quantum yields in both solution and the solid state. Regardless of this limitation, thiophene-based materials still provide a number of characteristics that have made them popular systems for technological applications. In addition to the stability and synthetic diversity already discussed, these characteristics include controllable color tuning of absorption and emission, good charge mobility, and the ability to produce materials with low band gaps. The interest in emissive thiophene derivatives has also increased due to various approaches for overcoming the commonly reduced fluorescence efficiencies, as well as new applications such as fluorescent biomarkers.

Besides the emissive properties, thiophene-based functional materials for photochromic systems are also studied intensively. Molecules in this category are usually termed "dithienylethene" concerning the structural motif of two thiophene rings bridged at their third position with an ethene group. Dithienylethenes (DTEs) outperform other photochromic systems in many ways, such as their excellent thermal stability in both isomers, high fatigue resistance, and switchability in the crystalline state. Before and after the irradiation, the two isomers differ not only in the absorption spectra but also in various physical and chemical properties, such as refractive indices, dielectric constants, oxidation-reduction potentials, and geometrical structures. The instant property changes without processing lead to their use in various optoelectronic devices, such as optical memory, photo-optical switching, display, and nonlinear optics. […]