Polymer solar cells (PSCs) have attracted considerable attention due to their advantages of light-weight

flexibility

solution-processibility to produce low-cost and large-area devices. At present

the PSCs are still at the research stage in laboratory. The researches in this field still focus on further improving the performance and the stability. Developing new and high-performance materials is one of the most important approaches to continually improve the device performance of PSCs. Donor-Acceptor (D-A) copolymers have the merits of wide absorption range

tunable energy levels

strong intramolecular charge transfer via " push-pull" effect

which has become an important material design strategy in PSCs. Tremendous electron-rich and electron-deficit skeletons have been employed as donor and acceptor units to build D-A conjugated copolymers. Among them

naphthobisthiadiazole and its fused-ring acceptor units possess large rigid planar conjugations and strong electron-withdrawing features

which have been used to develop highly efficient polymer donor materials. In this review

we present an overall view of the recent progress of the naphthobisthiadiazole and its fused-ring acceptor units-based conjugated copolymer materials and their applications in PSCs.