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Over the past decade, isoindigo has become a widely used electron‐deficient subunit in donor‐acceptor organic semiconductors, and these isoindigo‐based materials have been widely used in both organic photovoltaic (OPV) devices and organic field effect transistors (OFETs). Shortly after the development of isoindigo‐based semiconductors, researchers began to modify the isoindigo structure in order to change the optoelectronic properties of the resulting materials. This led to the development of many new isoindigo‐inspired compounds; since 2012, the Kelly Research Group has synthesized a number of these isoindigo analogues and produced a variety of new donor‐acceptor semiconductors. In this Personal Account, recent progress in the field is reviewed. We describe how the field has evolved from relatively simple donor‐acceptor small molecules to structurally complex, highly planarized polymer systems. The relevance of these materials in OPV and OFET applications is highlighted, with particular emphasis on structure‐property relationships. [ABSTRACT FROM AUTHOR]

This personal account describes the pursuit of non‐fullerene acceptors designed from simple and accessible organic pi‐conjugated building blocks and assembled through efficient direct (hetero)arylation cross‐coupling protocols. Initial materials development focused on isoindigo and diketopyrrolopyrrole organic dyes flanked by imide‐based terminal acceptors. Efficiencies in solution‐processed organic solar cells were modest but highlighted the potential of the material design. Materials performance was improved through structural engineering to pair perylene diimide with these organic dyes. Optimization of active layer processing and solar cell device fabrication identified the perylene diimide flanked diketopyrrolopyrrole structure as the best framework, with fullerene‐free organic solar cells achieving power conversion efficiencies above 6 %. This material has met our criteria for a simple wide band gap fullerene alternative for pairing with a range of donor polymers. [ABSTRACT FROM AUTHOR]