2-Alkyl (1) alkyl (2) -type aliphatic side chains with a branching point position at the C 2 -position (such as 2-ethylhexyl or 2-octayldodecyl) have been widely implanted into numerous donor−acceptor conjugated copolymers for solution processable transistors or organic solar cells. However, the tertiary branching site located at the second carbon inevitably imposes steric hindrance that twists the main-chain coplanarity and attenuates interchain interactions. In this research, we developed a new two-dimensonal thiophene−vinylene−thiophene (TVT) derivative where a carbon−carbon triple bond is inserted between the thiophene unit and the 2-octyldodecyl group. This acetylene-incorporated TVT (aTVT) was copolymerized with 5,10-di(thiophen-2-yl)naphtho[1,2-c:5,6-c′]bis-([1,2,5]thiadiazole) (DTNT) and 5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (DTFBT) to form the polymers PaTVT-NT and PaTVT-FBT, respectively. PTVT-FBT, without the triple bond, was also prepared for comparison. The insertion of a linear triple bond moves the tertiary carbon away from the main chain to reduce the steric hindrance, thereby improving the main-chain coplanarity and facilitating the interchain interactions. The acetylene-incorporated copolymers show better thermal stability, red-shifted absorption spectra, stronger intermolecular aggregation, lower-lying electron affinity, and much higher solid-state crystallinity. Due to the linear and coplanar polymeric backbone supported by theoretical calculation, PaTVT-NT exhibits high crystallinity and adopts strong stacking with an edge-on orientation in the thin film evidenced by 2D-GIXRD, leading to a high p-type OFET mobility up to 1.27 cm 2 V −1 s −1 with an on−off ratio of 9.22 × 10 5 . This value represents the highest value among the NT-based polymers. PaTVT-FBT also achieved a high mobility of 0.78 cm 2 V −1 s −1 , which greatly outperforms the corresponding nonacetylene PTVT-FBT counterpart. Most importantly, the preparation of 2-alkyl (1) alkyl (2) −acetylenyl side chain is synthetically feasible, which can be easily applied to create new conjugated polymers for high-performance solution-processable optoelectronics.
An angular-shaped dialkyltetracenedithiophene monomer undergoes [4+4] photodimerization to form a single “butterfly-shaped dimer” syn-[2,2]-daTDT with regio- and stereo-selectivity.
We discovered a unique synthetic
route to construct 2H-pyran-containing
tetracyclic dithienocyclopentapyran (DTCP) and dibenzocyclopentapyran
(DBCP) architectures. The synthesis involves an acid-induced dehydration
cyclization followed by a [1,5] hydride-shift isomerization to form
a cyclopentanone moiety which was converted to the pyran-embedded
tetracyclic products by a CuI-catalyzed intramolecular C–O
bond formation in good yield. DTCP was used as a building block to
prepare an acceptor–donor–acceptor (A–D–A)
type n-type material DTCP-BC leading to a solar cell efficiency of
9.32%.
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