- Development of s-tetrazine-based polymers for efficient polymer solar cells by controlling appropriate molecular aggregation
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Two conjugated polymers PTTTz and PHTTz have been designed and synthesized by introducing s-tetrazine as electron-withdrawing moieties. Compared with PTTTz with 2-octyldodecyl-substituted tetrathiophene derivative as electron-donating moieties, PHTTz with hexyl- and 2-octyldodecyl-substituted hexathiophene derivative possesses relatively lower molecular coplanarity, larger stacking distance but more orderly molecular stacking, more red-shifted absorption, more suitable microphase separation, more efficient exciton dissociation, higher hole mobility, which lead to higher short-circuit current density (11.54 mA cm?2), fill factor (69.0%) and power conversion efficiency (PCE = 6.69%) values in PSCs. The PTTTz-based PSC shows an open circuit voltage of 1.02 V for its lower-ling HOMO energy level though the PCE of the PSC is only 5.16%. Moreover, the ternary PSC based PHTTz/PC71BM/ITIC exhibits a higher PCE value of 7.88% than the binary PSCs for more efficient exciton dissociation and complementary absorption spectrum in ternary blend film, which is one of the highest PCE values in s-tetrazine-based polymers.
- Peng, Lini,Yu, Yufu,Lu, Jie,He, Pingxiang,Wang, Guo,Huang, Meihua,Zhao, Bin,Pei, Yong,Tan, Songting
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- Intermolecular Arrangement of Fullerene Acceptors Proximal to Semiconducting Polymers in Mixed Bulk Heterojunctions
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Precise control of the molecular arrangements at the interface between the electron donor and acceptor in mixed bulk heterojunctions (BHJs) remains challenging, despite the correlation between structural characteristics and efficiency in organic photovoltaics (OPVs). This study reveals that the substitution patterns of linear and branched alkyl side chains on electron-donating/-accepting alternating copolymers can control the positions of an acceptor molecule (C60) around the π-conjugated main chains in mixed BHJs. Two-dimensional solid-state NMR demonstrates a marked difference in the location of C60 in the blend films. A copolymer with an electron-accepting unit positioned in close proximity to C60 demonstrated higher OPV performance in combination with various fullerene derivatives. This molecular design offers precise control over the interfacial molecular structure, thereby paving the way for overcoming the current limitations of OPVs comprising mixed BHJs.
- Wang, Chao,Nakano, Kyohei,Lee, Hsiao Fang,Chen, Yujiao,Hong, You-Lee,Nishiyama, Yusuke,Tajima, Keisuke
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supporting information
p. 7034 - 7039
(2018/06/15)
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- Synthesis and optical properties of photovoltaic materials based on the ambipolar dithienonaphthothiadiazole unit
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Dithieno[3′2′:5,6;2′′,3′′:7,8]naphtho[2,3-c][1,2,5]thiadiazole (DTNT) was designed to control the band energies of the polymers for photovoltaic materials. Electrochemical analysis showed that DTNT acts as both an electron donor and an electron acceptor, revealing the ambipolar nature of the DTNT unit. The direct arylation polymerization of DTNT with 2,2′-bithiophene (BTh) and 3,6-bis(2-thienyl)pyrrolo[3,4-c]pyrrole-1,4-dione (DPP) afforded four polymers that differed in either the unit of copolymerization or the chosen side chains. In the PDTNT-BTh series, a shoulder absorption band was observed at a longer wavelength than the intense absorption band. The PDTNT-DPP series exhibited a narrow band gap of less than 1.4 eV and a low HOMO energy of -5.43 eV. An organic photovoltaic cell that contained a PDTNT-BTh polymer with 2-ethylhexyl groups and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) as an active layer afforded the best performance among the studied compounds, with a JSC of 6.98 mA cm-3, a VOC of 0.758 V, a FF of 0.52, and a PCE of 2.76%.
- Nakanishi, Tatsuaki,Shirai, Yasuhiro,Han, Liyuan
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supporting information
p. 4229 - 4238
(2015/03/04)
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