Abstract
A series of novel p-type conjugated copolymers, PTTVBDT, PTTVBDT-TPD, and PTTVBDT-DPP, cooperating benzo[1,2-b:4,5-b′]dithiophene (BDT) and terthiophene-vinylene (TTV) units with/without thieno[3,4-c]pyrrole-4,6-dione (TPD) or pyrrolo[3,4-c]pyrrole-1,4-dione (DPP) via Stille polymerization were synthesized and characterized. Copolymer PTTVBDT shows a low-lying HOMO energy level and ordered molecular-packing behavior. Furthermore, two terpolymers, PTTVBDT-TPD and PTTVBDT-DPP, display stronger absorption ability, alower-lying HOMO energy level, and preferred molecular orientation, due to the replacement TTV-monomer units with electron-deficient groups. Furthermore, bulk-heterojunction organic solar cells were fabricated using blends of the PTTVBDT-TPD, and PC61BM gave the best power conversion efficiency of 5.01% under the illumination of AM 1.5G, 100 mW·cm−2; the short circuit current (Jsc) was 11.65 mA·cm−2 which displayed a 43.8% improvement in comparison with the PTTVBDT/PC61BM device. These results demonstrate a valid strategy combining the two-dimensional molecular structure with random copolymerization strikes promising conjugated polymers to achieve highly efficient organic photovoltaics.
Highlights
M2 and M4 were synthesized by reported methods [31,32,34]; M1 was synthesized via the HornerThe synthetic routes of the monomers and copolymers are shown in Scheme 1
4,6(5H)-dione 4, which is the microwave-assisted Stille cross-coupling reaction product of 1,3M3 was synthesized from the bromination of 5-octyl-1,3-di(thiophen-2-yl)-4H-thieno[3,4-c]pyrroledichloro-5-octyl-4H-thieno[3,4-c]pyrrole-4,6(5H)-dione 3 and tributyl(thiophen-2-yl)stannane
Regardless, these results reveal that the PTTVBDT-based these results reveal that the PTTVBDT-based polymer exhibit ordered orientations which is apolymer critical exhibit ordered orientations which is a critical property in conjugated polymers for application in property in conjugated polymers for application in electronic devices, especially and electronic devices, especially and PTTVBDT-DPP, a preferred
Summary
Development of novel semiconducting conjugated polymers and investigation ofstructure–property relationships always play a critical role in the organic electronic devices. As a promising conjugated polymer in the OPV field, it should possess broad absorption in the solar spectrum, high charge carrier mobility for charge transport, suitable energy. Themolecular designs of the molecular can be their used properties to control their particular importance in the development conjugated polymers. DPP conjugated units both widely used as building blocks and electron-withdrawing groups in high performance have been widely used as building blocks and electron-withdrawing groups in high performance conjugated polymers due to their symmetric, rigidly fused, and coplanar structures [11,27,28,29,30].
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