With the rapid evolution of photovoltaic polymer materials, power conversion efficiency of polymer solar cells has been markedly improved in recent years, and is now approaching a landmark value of 10 %. This review focuses on Donor-Acceptor (D-A) photovoltaic copolymers. Starting from briefly introducing the D-A concept, the fundamental donor and acceptor units for constructing polymer photovoltaic materials are introduced and classified. By summarizing the structure-property relationships of typical photovoltaic D-A copolymers, the important design rules for such materials are highlighted. Several crucial aspects, including proper combination of D-A units, high planarity of the backbone and proper incorporation of side chains are particularly emphasized. A new D-A architecture, namely main-chain donor and side-chain acceptor is introduced and reviewed. Moreover, the role of the electron-deficient group in fine-tuning energy levels of low-bandgap D-A photovoltaic polymers is discussed.

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