Ladder-Type Dithienonaphthalene-Based Donor鈥揂cceptor Copolymers for Organic Solar Cells

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• 作者：Yunlong Ma ; Qingdong Zheng ; Zhigang Yin ; Dongdong Cai ; Shan-Ci Chen ; Changquan Tang
• 刊名：Macromolecules
• 出版年：2013
• 出版时间：June 25, 2013
• 年：2013
• 卷：46
• 期：12
• 页码：4813-4821
• 全文大小：544K
• 年卷期：v.46,no.12(June 25, 2013)
• ISSN：1520-5835

文摘

A novel ladder-type dithienonaphthalene (DTN) was designed and synthesized as an electron-rich unit for constructing donor鈥揳cceptor copolymers. Different acceptor moieties, including benzo[c][1,2,5]thiadiazole (BT), 5,6-bis(hexyloxy)-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (TBT), and 2,5-bis(2-ethylhexyl)-3,6-di(thiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (TDPP), were used as electron-deficient units for the target copolymers. These copolymers (PDTNBT, PDTNTBT, and PDTNTDPP) were obtained via the Stille coupling reaction and characterized by ¹H NMR spectroscopy, UV鈥搗is absorption spectroscopy, cyclic voltammetry, and gel permeation chromatography (GPC). Owing to the four solubilizing alkyl chains on the DTN unit, all the three copolymers have good solubility in common solvents. Among these polymers, PDTNTBT exhibits the highest space-charge limit current (SCLC) hole mobility of 2.13 脳 10^鈥? cm² V^鈥? s^鈥?, which is beneficial for achieving high performance solar cells. Under the simulated AM 1.5G illumination condition (100 mW/cm²), solar cells based on PDTNTBT:PC₇₁BM (1:3, w/w) exhibit a power conversion efficiency (PCE) of 4.8% with a current density of 10.3 mA cm^鈥?, an open-circuit voltage of 0.86 V, and a fill factor of 54%. With the same device fabrication method, PDTNTDPP:PC₇₁BM (1:3, w/w) and PDTNBT:PC₇₁BM (1:3, w/w) based devices exhibit efficiencies of 1.52% and 2.79%, respectively. Furthermore, inverted solar cells based on these copolymer blends are also fabricated. The inverted devices based on PDTNTDPP:PC₇₁BM (1:2, w/w) and PDTNBT:PC₇₁BM (1:2, w/w) exhibit PCEs of 1.60% and 2.89%, respectively, which are similar to their corresponding conventional devices. And the inverted devices based on PDTNTBT:PC₇₁BM (1:2, w/w) show a higher PCE of 5.0%, and more importantly, they are quite stable as demonstrated by the 4.75% PCE after ambient storage for two months.