Wu, H.-C.H.-C.WuLai, Y.-C.Y.-C.LaiChiu, Y.-C.Y.-C.ChiuLee, W.-Y.W.-Y.LeeWEN-CHANG CHEN2018-09-102018-09-102014http://www.scopus.com/inward/record.url?eid=2-s2.0-84898007760&partnerID=MN8TOARShttp://scholars.lib.ntu.edu.tw/handle/123456789/385492Novel biaxially extended octithiophene (8T)-based conjugated polymers are successfully synthesized using Stille coupling reactions of the branched octithiophene moiety with selenophene (P8TSe), thiophene (P8TT), and thieno[3,2-b]thiophene (P8TTT). The 8T moiety can significantly lower the highest occupied molecular orbital (HOMO) level and leads to an enhanced open-circuit voltage because of the branched conformation. The power conversion efficiencies (PCE) of the polymer/[6,6]-phenyl-C71-butyric acid methyl ester PC71BM photovoltaic cells are in the range of 1.28-2.30%. In particular, the P8TTT-based device processed from an o-dichlorobenzene/1,8- diiodoctane mixed solvent shows the best PCE among the studied polymers (2.81%), demonstrating that 8T-based polymers with a low HOMO level can emerge as promising candidates for organic device applications. Biaxially extended octithiophene (8T)-based polymers are developed with selenophene, thiophene, and thieno[3,2-b]thiophene moieties. The designed polymers possess low highest occupied molecular orbital (HOMO) levels, leading to an enhanced open-circuit voltage and solar-cell efficiency up to 2.81%. The results demonstrate that 8T-based polymers can enhance the optoelectronic properties and device performance through their branched molecular design. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.biaxially extended materials; branched thiophene side chains; conjugated polymers; high open-circuit voltage; photovoltaic cells[SDGs]SDG7Conjugated polymers; Open circuit voltage; Photoelectrochemical cells; Photovoltaic cells; Based conjugated polymers; Conjugated copolymers; Device performance; Highest occupied molecular orbital; Optoelectronic properties; Power conversion efficiencies; Side-chains; Stille coupling reaction; Thiophenejournal article10.1002/macp.2013007652-s2.0-84898007760WOS:000333742000006