Development of donor-acceptor copolymers based on dioxocycloalkene-annelated thiophenes as acceptor units for organic photovoltaic materials

Organic photovoltaics (OPVs) have attracted considerable attention over the past two decades not only because of their potential for generating renewable energy but also because of their favorable properties, such as low cost, low weight, solution processability and large-area manufacturability. The active layer of OPVs is based on the concept of the bulk-heterojunction configuration, which comprises a blend of a pi-conjugated polymer as an electron donor (p-type) and a fullerene derivative as an electron acceptor (n-type). Donor-acceptor (D-A) copolymers have been utilized as efficient p-type materials in OPVs. In this review, we will focus on a series of dioxocycloalkene-annelated thiophenes as novel acceptor units and summarize photophysical and electrochemical properties of D-A copolymers that contain these acceptor units as well as their OPV performance in combination with [6,6]-phenyl-C-x-butyric acid methyl ester (x=61 or 71). These systematic investigations will provide important insight for the development of high-performance D-A-type OPV materials.