ABSTRACT
An important topic in materials science in recent years has been the development of organic semiconductors and their extensive use in electronics and photonics applications such as organic solar cells (OPVs), organic field-effect transistors (OFETs), sensors, and photodetectors [1–4]. These materials are promising in terms of their electronic properties, low cost, versatility of functionalization, thin-film flexibility, easy fabrication, etc. The emergence of π-conjugated oligomers with discrete structures sequentially constructed from smaller organic building blocks is particularly inspiring. The appeal of such π-conjugated oligomers is their well-defined molecular structure, ease of purification, and good batch-to-batch reproducibility, which facilitates physical characterization and enables precise structure–property–performance relationships to be established [4–7]. Considerable efforts have been dedicated to developing novel π-conjugated oligomers for the aforementioned applications, and tremendous progress has been achieved [8–10]. For example, the use of indacenodithiophene (IDT)-based oligomers as acceptors has resulted in nonfullerene OPVs with power conversion efficiencies (PCEs) greater than 15014%, making these materials ideal candidates for high-performance OPVs [11, 12] In addition, highly crystalline π-conjugated oligomers generally exhibit a strong tendency to self-assemble into long-range-ordered structures, thereby contributing to high charge carrier mobilities in thin films [13–15]. Moreover, the electronic and structural properties of oligomers can be used as templates to yield valuable insights into the corresponding polymeric materials, such as to probe their mean conjugation length or their optical band gaps and to refine synthesis strategies [16, 17]. Therefore, π-conjugated oligomers are a promising family of semiconductor materials and have led to many recent exciting breakthroughs in the field of organic electronics.
