Incorporating two polymer donors with different bandgaps to compose a ternary blend bulk heterojunction (BHJ) is proved an effective approach to improve the device performance of BHJ polymer solar cells (PSCs). Here, A low band gap (LBG) polymer PDTP-DFBT is incorporated into PTB7:PC71BM host blend to compose a ternary blend system. Besides extending the absorption range, the crystallinity and preferred face-on orientation of PTB7 are simultaneously improved. Combining a cathod interfacial modification, a successful ternary blend PSC with a high efficiency 9.06% is achieved.

Fig (a) Molecular structures of PTB7, PDTP-DFBT and PC71BM; (b) Schematic inverted device structure; (c) J–V characteristics of the binary and ternary devices.
Shuhua Zhang, Lijian Zuo,* Jiehuan Chen, Zhongqiang Zhang, Jiangquan Mai,Tsz-Ki Lau, Xinhui Lu, Minmin Shi and Hongzheng Chen*

http://pubs.rsc.org/en/Content/ArticleLanding/2016/TA/c5ta09727d#!divAbstract