title: Selenium-substituted polymers for improved photovoltaic performance.
abstract: Four isostructural donor-acceptor alternating polymers of benzodithiophene (BDT)/naphthodifuran (NDF) and benzoselenadiazole (BSe)/benzothiadiazole (BT) have been developed and evaluated for organic photovoltaics. The substitution of one-atom (Se for S) in the accepting units exerts remarkable impact on the optoelectronic properties of polymers. Extended absorption, narrowed bandgap and higher HOMO energy levels were observed for Se-containing polymers in comparison to their S-containing counterparts. Theoretical calculations confirmed the measurable effect on energy levels as found in experimental studies. Bulk-heterojuction solar cells based on the BDT-BSe copolymer and [6,6]-phenyl-C71-butyric acid methyl ester (1 : 2, w/w) blend films deliver the best PCE of 5.40%. BSe-based polymers showed enhanced photovoltaic performances than BT-based polymers. The device performance is found to be strongly dependent on the processing conditions and morphology of the active layers.
authors.affiliation: Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education of China), Nanjing University of Science and Technology, Nanjing 210094, China. whtang@mail.njust.edu.cn.
authors.forename: Jiangsheng
authors.initials: J
authors.lastname: Yu
authors.affiliation: Institute of Functional Nano & Soft Materials (FUNSOM) & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou Industrial Park, Suzhou, Jiangsu 215123, China. wlma@suda.edu.cn.
authors.forename: Guanqun
authors.initials: G
authors.lastname: Ding
authors.affiliation: Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education of China), Nanjing University of Science and Technology, Nanjing 210094, China. whtang@mail.njust.edu.cn.
authors.forename: Jiefeng
authors.initials: J
authors.lastname: Hai
authors.affiliation: Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education of China), Nanjing University of Science and Technology, Nanjing 210094, China. whtang@mail.njust.edu.cn.
authors.forename: Enwei
authors.initials: E
authors.lastname: Zhu
authors.affiliation: Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education of China), Nanjing University of Science and Technology, Nanjing 210094, China. whtang@mail.njust.edu.cn.
authors.forename: Xinxing
authors.initials: X
authors.lastname: Yin
authors.affiliation: Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education of China), Nanjing University of Science and Technology, Nanjing 210094, China. whtang@mail.njust.edu.cn.
authors.forename: Zhongsheng
authors.initials: Z
authors.lastname: Xu
authors.affiliation: Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education of China), Nanjing University of Science and Technology, Nanjing 210094, China. whtang@mail.njust.edu.cn.
authors.forename: Baojing
authors.initials: B
authors.lastname: Zhou
authors.affiliation: Key Laboratory of Luminescence and Optical Information, Ministry of Education, Beijing Jiaotong University, Beijing, 100044, P. R. China. fjzhang@bjtu.edu.cn.
authors.forename: Fujun
authors.initials: F
authors.lastname: Zhang
authors.affiliation: Institute of Functional Nano & Soft Materials (FUNSOM) & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou Industrial Park, Suzhou, Jiangsu 215123, China. wlma@suda.edu.cn.
authors.forename: Wanli
authors.initials: W
authors.lastname: Ma
authors.affiliation: Key Laboratory of Soft Chemistry and Functional Materials (Ministry of Education of China), Nanjing University of Science and Technology, Nanjing 210094, China. whtang@mail.njust.edu.cn.
authors.forename: Weihua
authors.initials: W
authors.lastname: Tang