Structural Modification of Isoindigo-based Conjugated Materials towards Optoelectronic Applications

Abstract

Organic semiconductors have attracted significant attention due to their potential for easy fabrication, light weight, low cost, and better compatibility with the solution and roll-to-roll processes for making flexible large area devices such as organic photovoltaics (OPVs) and organic field-effect transistors (OFETs). Moreover, many attempts have been made to design and synthesize state-of-the-art organic semiconductors to enhance device performance. Nowadays, almost all active materials of organic semiconductors are based on π-conjugated molecular backbones synthesized by cross-coupling reaction methodologies. Recently, organic dyes have emerged as high-performance conjugated materials that have strong electron-withdrawing characters, intermolecular interaction, good planarity, relatively reduced energy band gaps, and high charge carrier transports. However, the confident performance in exceeds of inorganic semiconductors is the most important requirement for enabling the realization of the aforementioned near-future products. Here, a synthesis method for the structural modification of isoindigo (IIG)-based conjugation materials (e.g., counterpart, thiophene-implanted thienoisoindigo (TIIG), and side-chain) and their optoelectronic applications are introduced. First, I present n-type charge carrier transports via IIG-based acceptor-acceptor (A-A type) copolymers, which can be extended to the design of new n-type materials. In addition, the implantation of heteroaromatic spacers into the A-A type copolymer makes donor-acceptor alternating copolymers for the polarity tuning of the OFETs. In the second part, TIIG alternate naphthalene copolymers are synthesized for p-type OFETs. The TIIG copolymers exhibit the highest p-type charge carrier mobility and a unique crystalline orientation. Finally, non-ionic phosphonate side-chains combined with IIG copolymers are synthesized to improve inverted OPVs, improving power conversion efficiency compared to without modified copolymers. This is a promising method for either the modification of IIG-based organic semiconducting materials or the enhancement of organic optoelectronics.