Thiophene–Vinylene–Thiophene-Based Donor–Acceptor Copolymers with Acetylene-Inserted Branched Alkyl Side Chains To Achieve High Field-Effect Mobilities

Abstract

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.

Influence of Backbone Regioregularity on High-Mobility Conjugated Polymers Based on Alkylated Dithienylacrylonitrile

“…Their solubility limits were calculated with their UV–vis–NIR absorption spectra according to the Beer–Lambert law. , The solubilities of the regioregular polymer RR-PDPPCNTVT-6 in the solvent of toluene, CHCl 3 , and o -DCB were 14.1, 14.2, and 22.8 mg mL –1 , respectively, which were a little lower than those of the regioirregular polymer RI-PDPPCNTVT-6. The high solubilities may be due to the combination side-chain effect of 2-decyltetradecyl alkyl chains on the DPP moieties and hexyl alkyl chains , on the CNTVT units. As both copolymers exhibited high solubilities in halogenated or nonhalogenated solvents, the solution-processing OFET fabrications for both polymers are feasible.…”

Control over Kinetic and Thermodynamically Driven Pathways of Crystallization to Yield Cofacial and Slipped‐Stack Dimers in Single Crystals

“…[18] Thermodynamicc onsiderations deal with the stabilityo ft he respective polymorphs, whichu suallyd iffer only by af ew kilojoules per mole,w hile kinetic pathways determine how fast the polymorphs are formed, whichd epends on their activation barriers for nucleation. [19,20] From the molecular point of view,c rystallisationo facertainp olymorph can be regarded as as upramolecular reaction involving the initial self-assembly of the molecules into energeticallys uitablea ggregates due to noncovalenti ntermolecular interactions followed by transformation into a3 Ds tructure. [21,22] Herein, we present ad onor-acceptor-type small-molecule compound in which thiophene and rhodamine groupsa re the donor anda cceptoru nits, respectively (25TR).…”

Ester-Functionalized Naphthobispyrazine as an Acceptor Building Unit for Semiconducting Polymers: Synthesis, Properties, and Photovoltaic Performance

“…A variety of acceptor units have been widely explored. Typical acceptor units incorporated into the polymer backbone include imide- and amide-based compounds, − o -quinoidal heterocycles, − and thienoquinoidal compounds. , With respect to o -quinoidal heterocycles, naphthalene-based electron-deficient π-conjugated systems, such as naphtho­[1,2- c :5,6- c ′]­bis­[1,2,5]­oxadiazoles (NOz), , naphtho­[1,2- c :5,6- c ′]­bis­[1,2,5]­thiadiazoles (NTz), − naphtho­[1,2- c :5,6- c ′]­bis­[1,2,5]­selenadiazoles (NSz), naphtho­[1,2- c :5,6- c ′]­bis­(2-substituted)-[1,2,3]­triazole (TZNT), , and naphtho­[1,2- b :5,6- b ′]­bispyrazine (NPz), − have been frequently utilized as building units to realize high-performance semiconducting polymers (Figure , upper panel). In fact, the performance of semiconducting polymers based on these building units has surpassed that of amorphous silicon in both transistors and organic photovoltaic (OPV) devices. − ,, …”

“…In fact, the performance of semiconducting polymers based on these building units has surpassed that of amorphous silicon in both transistors and organic photovoltaic (OPV) devices. [34][35][36][37][38]40,46 Among the naphthalene-based acceptor units, NPz has been the least investigated. Importantly, however, NPz allows the introduction of four substituents at the 2, 3, 8, and 9 positions, in contrast to other naphthalene-based acceptor units that do not do so (NOz, NTz, NSz), or that allow the introduction of only two substituents at the N-position (TZNT).…”