Structure-property relationship of D-A type copolymers based on thienylenevinylene for organic electronics

Diazapentalene-Containing Ultralow-Band-Gap Copolymers for High-Performance Near-Infrared Organic Phototransistors

“…3,6-Di(thiophen-2-yl)pyrrolo [3,4-c]pyrrole-1,4(2H,5H)-dithione (1) and its counterpart monomers of 2,5-bis(trimethylstannyl)furan, 2,5bis(trimethylstannyl)thiophene, and 2,5-bis(trimethylstannyl)selenophene were prepared according to reported procedures. 1 H NMR and 13 C NMR spectra of the monomers were recorded on a Bruker Avance III HD 400 MHz spectrophotometer using deuterated CDCl 3 as the solvent and tetramethylsilane (TMS) as an internal standard. In addition, 1 H NMR spectra of the resulting copolymers were recorded by a VNMRS 600 (Agilent, USA) spectrophotometer using deuterated 1,1,2,2-tetrachloroethane-d 2 as the solvent with TMS as an internal standard.…”

“…Low-band-gap π-conjugated polymers, which absorb in the near-infrared (NIR) range (760–1100 nm) with a typical band gap smaller than 1.6 eV, are an interesting family of semiconductor materials and have enabled many recent exciting breakthroughs in various functional optoelectronic applications, such as organic field-effect transistors (OFETs), organic photodetectors (OPTs), and electrochromic devices. − Indeed, incorporating a quinoid structure into the polymer backbone is a powerful strategy for reducing the band gap, which has been verified by theoretical and experimental studies of the well-known poly­(isothianaphthene) and poly­(thieno­[3,4- b ]­pyrazine), − which exhibit band gaps of less than 1.0 eV. However, such quinoid-type polymers typically have a very small band gap and poor stability toward oxidation, which renders them difficult to be employed in the aforementioned devices. , Alternatively, utilizing donor–acceptor (D–A) interactions (so-called D–A-type copolymers) is emerging as a mainstream approach for constructing low-band-gap polymers in which electron-rich (donor) and electron-deficient (acceptor) building units are alternately regulated along the backbone. − D–A-type copolymers offer the unique possibility of tuning their energy levels (the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) levels) almost independently as well as their band gaps. , Thus, introducing a strong acceptor unit into the main backbone can lower the LUMO while retaining a relatively low HOMO, thereby leading to a reduced band gap and improved stability against the oxidation of the resulting copolymers.…”

Chlorinated Isoindigo-Based Conjugated Polymers: Effect of Rotational Freedom of Conjugated Segment on Crystallinity and Charge-Transport Characteristics

“…However, it is known, that when the conjugated backbone has flexible segments, it can help the chain rearrangement during the thermal annealing process due to higher rotational freedom. 4,28 Therefore, it is expected, that the low film crystallinity and chain orientation of the conjugated polymer induced by the large size of a chlorine atom can be improved by introducing a flexible segment, which can maximize the thermal annealing effect, into the polymer backbone. Moreover, we can further understand the structure− property relationship of the chlorine-substituted conjugated polymer, which can result in contributing to an improvement in the n-type performance of OFET.…”

“…Because of these advantages, research about introducing a chlorine atom into the conjugated backbone has been reported, − but it is still less investigated than that of the fluorine atom, presumably, due to the large size of a chlorine atom, which induces steric hindrance effects in the conjugated backbone. , The large steric hindrance in the conjugated backbone might disturb the film crystallinity and chain orientation. However, it is known, that when the conjugated backbone has flexible segments, it can help the chain rearrangement during the thermal annealing process due to higher rotational freedom. , Therefore, it is expected, that the low film crystallinity and chain orientation of the conjugated polymer induced by the large size of a chlorine atom can be improved by introducing a flexible segment, which can maximize the thermal annealing effect, into the polymer backbone. Moreover, we can further understand the structure–property relationship of the chlorine-substituted conjugated polymer, which can result in contributing to an improvement in the n -type performance of OFET.…”

Molecular engineering of benzothiadiazole-based polymers: balancing charge transport and stretchability in organic field-effect transistors

“…In solution, all copolymers exhibited an intramolecular charge transfer transition with absorption maxima (l max ) at 574 nm for P1, 609 nm for P2 and 577 nm for P3 nm, as well as, pronounced shoulder suggesting strong intramolecular interactions due to aggregation in solution. 41,42 In comparison, both P1 and P3 display a bathochromic shift (18-36 nm) in their film absorption spectra, with absorption maxima at 610 nm for P1 and 595 for P3. However, P2 (bearing both fluorine and alkyl side chain) does not show a significant shift, which can be attributed to the structural asymmetry impacting solid-state packing.…”