Thienoisoindigo-based low-band gap polymers for organic electronic devices

Abstract

We synthesized a series of new low-band gap donor-acceptor copolymers containing 4,4 0 -bis(alkyl)-[6,6 0 -bithieno[3,2-b]pyrrolylidene]-5,5 0 (4H,4 0 H)-dione. This acceptor unit, so-called dithienoketopyrrole (DTKP), is an analogue of isoindigo, the phenyl rings of which are replaced by thiophenes. Donor moieties such as benzodithiophene, cyclopentadithiophene, fluorene, and dithienothiophene are polymerized with DTKP in an alternating fashion by Stille or Suzuki-Miyaura coupling methods. Exceedingly low-band gaps (E g ¼ 1.0-1.6 eV) were achieved in these copolymers through internal charge transfer interactions between the donor and acceptor moieties. The structural, photophysical, and electrochemical properties of the resultant copolymers were characterized, and field-effect transistor (FET) mobilities were measured. The copolymers showed electronic absorption spectra extending to the near infrared region (600-1400 nm) with absorption maxima at 745-971 nm, along with a low-lying LUMO of À3.8 eV. Density functional theory (DFT) calculation indicated high planarity for the copolymer backbone when compared to that of its phenyl-isoindigo counterparts. FET hole mobilities on the order of 10 À4 to 10 À3 cm 2 V À1 s À1 were obtained, demonstrating a feasibility to use them in organic photovoltaic cells.

Effects of branching position of alkyl side chains on ordering structure and charge transport property in thienothiophenedione- and quinacridone-based semiconducting polymers

“…3 In the development of semiconducting polymers, the design of the conjugated backbone is of primary importance because it substantially affects the molecular orbital energies, [4][5][6] bandgaps, 7,8 and ordering structure 9,10 that determine the device performance of the polymers. To date, enormous effort has been focused on the exploration of backbone structures (that is, new conjugated building units and their combinations).…”

Control of Phase Separation of Benzothienoisoindigo-Benzodithiophene Copolymer for Organic Photovoltaics

“…40 nm from that in solution with the appearance of vibronic peak. This is contrary to the TIDG copolymer [15], and explained by moderated intramolecular charge transfer interaction between donor and BTIDG units and extension of -conjugation.…”

“…developed [15][16][17][18], while the best PCE is limited to 2.55% of the thiophene-appended BDT-TIDG copolymer [19]. TIDG demonstrates a high planarity and strong electron affinity in nature, which allows extending photoabsorption to near infrared region [15], and thus, TIDG is attempted to be coupled with various donor units [20][21][22][23].…”

“…TIDG demonstrates a high planarity and strong electron affinity in nature, which allows extending photoabsorption to near infrared region [15], and thus, TIDG is attempted to be coupled with various donor units [20][21][22][23]. The constrained low PCEs are partly ascribed to the short lifetime of singlet exciton [16] associated with energy gap law [24].…”

Synthesis of a novel water-soluble conjugated polyelectrolyte based on polycyclopentadithiophene backbone and its application for heparin detection

“…Recently, PCPDT and its derivatives have been applied as novel photoelectrical materials because of their remarkably optical and electrical properties. [16,17] However, very few bio-applications using water-soluble CPE based on PCPDT backbone have been reported. In order to broaden the application of PCPDT such as biodetection or protein sensor, new cationic-CPE poly[(4,4-bis(3ʹ-N,N,N-trimethylammonium) propyl) cyclopentadithiophene dichloride] is first synthesized and applied as the sensor for heparin.…”