Indolo- and Diindolocarbazoles in Organic Photovoltaic Cells

Over the past decades, indolo- and diindolocarbazoles have been incorporated in bulk heterojunction solar cells (BHJSCs) as electron donors - either as small molecules or within the backbone of conjugated push-pull polymers. Recently, these units were used as nonfullerene electron acceptors, resulting in superior photoconversion efficiencies (PCEs). Their motif consists of D-A or A-D-A units (D = electron-donor; A = electron-acceptor). This review focuses on the reasons why that is so.