Construction of a long range p/n heterojunction with a pair of nanometre-wide continuous D/A phases

A p/n heterojunction is the basic setup for light-electric conversion. It has been widely accepted that the ideal configuration for organic photovoltaics is formed by the joint of a pair of long-range continuous but nanometre-wide phases consisting of electron-donating (D) and -accepting (A) components, respectively. Such a p/n heterojunction can provide not only a large D/A interface essential to efficient photoinduced charge separation, but also the transportation pathways for both electrons and holes. This review article summarizes the present approaches including D-A double cables, diblock copolymers, and small molecular D-A dyads and multiads, to construct such an ideal p/n heterojunction. Each approach is introduced by a few selected representative works, with highlights on their molecular design strategies and the relationship of chemical structure-packing order-property. Such information would be useful for the next research in the field.