Synthesis and Characterization of Angular-Shaped Naphtho[1,2-b;5,6-b′]difuran–Diketopyrrolopyrrole-Containing Copolymers for High-Performance Organic Field-Effect Transistors

Recent Advances of Furan and Its Derivatives Based Semiconductor Materials for Organic Photovoltaics

The state-of-the-art bulk-heterojunction (BHJ)-type organic solar cells (OSCs) have exhibited power conversion efficiencies (PCEs) of exceeding 18%. Thereinto, thiophene and its fused-ring derivatives play significant roles in facilitating the development of OSCs due to their excellent semiconducting natures. Furan as thiophene analogue, is a ubiquitous motif in naturally occurring organic compounds. Driven by the advantages of furan, such as less steric hindrance, good solubility, excellent stacking, strong rigidity and fluorescence, biomass derived fractions, more and more research groups focus on the furan-based materials for using in OSCs in the past decade. To systematically understand the developments of furan-based photovoltaic materials, the relationships between the molecular structures, optoelectronic properties, and photovoltaic performances for the furan-based semiconductor materials including single furan, benzofuran, benzodifuran (BDF) (containing thienobenzofuran (TBF)), naphthodifurans (NDF), and polycyclic furan are summarized. Finally, the empirical regularities and perspectives of the development of this kind of new organic semiconductor materials are extracted.

Effects on Photovoltaic Performance of Dialkyloxy-benzothiadiazole Copolymers by Varying the Thienoacene Donor

A series of four donor-acceptor alternating copolymers based on dialkyloxy-benzothiadiazole (ROBT) as an acceptor and thienoacenes as donor units were synthesized and tested for polymer solar cells (PSCs). These new polymers had different donor units with varied electron-donating ability (thieno[3,2-b]thiophene (TT), dithieno[3,2-b:2',3'-d]thiophene (DTT), benzo[1,2-b:4,5-b']dithiophene (BDT), and naphtha[1,2-b:5,6-b']dithiophene (NDT)) in the polymer backbone. To understand the effect of these thienoacenes on the optoelectronic and photovoltaic properties of the copolymers, we systematically analyzed and compared the energy levels, crystallinity, morphology, charge recombination, and charge carrier mobility in the resulting polymers. In this series, optimized photovoltaic cells yielded power conversion efficiency (PCE) values of 6.25% (TT), 9.02% (DTT), 6.34% (BDT), and 2.29% (NDT) with different thienoacene donors. The introduction of DTT into the thienoacene-ROBT polymer enabled the generation of well-ordered molecular packings with a π-π stacking distance of 3.72 Å, high charge mobilities, and an interconnected nanofibrillar morphology in blend films. As a result, the PSC employing the polymer with DTT exhibited the highest PCE of 9.02%. Thus, our structure-property relationship studies of thienoacene-ROBT-based polymers emphasize that the molecular design of the polymers must be carefully optimized to develop high efficient PSCs. These findings will help us to understand the impact of the donor thienoacene on the optoelectronic and photovoltaic performance of polymers.

Synthesis and characterization of acceptor–donor–acceptor-based low band gap small molecules containing benzoselenadiazole

Acceptor–donor–acceptor-type compounds 5′,5″-(benzo[c][1,2,5]selenadiazole-4,7-diyl)bis(3′-dodecyl-2,2′-bithiophene-5-carbonitrile) (9) and 4,4′-(5,5′-(benzo[c][1,2,5]selenadiazole-4,7-diyl)bis(3-dodecylthiophene-5,2-diyl))dibenzonitrile (10) were designed and synthesized. These compounds differ in terminal positions, compound 9 with a thiophene-containing nitrile group and compound 10 with a phenyl-containing nitrile group. Both compounds have shown good thermal stability and low band gap. The band gaps of compounds 9 and 10 were 1.74 and 1.83 eV, respectively. These results indicate that they are promising materials for use in optoelectronics.

Syntheses of dibenzo[d,d']benzo[2,1-b:3,4-b']difuran derivatives and their application to organic field-effect transistors

Ladder-type π-conjugated compounds containing a benzo[2,1-b:3,4-b']difuran skeleton, such as dibenzo[d,d']benzo[2,1-b:3,4-b']difuran (syn-DBBDF) and dinaphtho[2,3-d:2',3'-d']benzo[2,1-b:3,4-b']difuran (syn-DNBDF) were synthesized. Their photophysical and electrochemical properties were revealed by UV-vis absorption and photoluminescence spectroscopy and cyclic voltammetry. Organic field-effect transistors (OFETs) were fabricated with these compounds as organic semiconductors, and their semiconducting properties were evaluated. OFETs with syn-DBBDF and syn-DNBDF showed typical p-type characteristics with hole mobilities of <1.5 × 10(-3) cm(2)·V(-1)·s(-1) and <1.0 × 10(-1) cm(2)·V(-1)·s(-1), respectively.

Incorporation of benzothiadiazole into the backbone of 1,2,5,6-naphthalenediimide based copolymers, enabling much improved film crystallinity and charge carrier mobility

By incorporating benzothiadiazole units into the main chain of 1,2,5,6-naphthalenediimide based copolymers, we report herein a new copolymer with much improved film crystallinity and charge carrier mobility.

Effect of donor strength of extended alkyl auxiliary groups on optoelectronic and charge transport properties of novel naphtha[2,1-b:6,5-b']difuran derivatives: simple yet effective strategy

The present study spotlights the designing of new derivatives of 2,7-bis (4-octylphenyl) naphtho [2,1-b:6,5-b'] difuran (C8-DPNDF) by substituting the alkyl groups (methyl, ethyl, propyl, butyl, pentyl, hexyl, and heptyl groups) at para position. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) methods are employed to optimize the molecular structures in ground and first excited states, respectively. Several electro-optical properties including hole/electron reorganization energies (λh/λe), electron affinities (EAs), ionization potentials (IPs), molecular electrostatic potentials (MEP), and frontier molecular orbitals (FMOs) have been evaluated. Furthermore their transfer integrals and intrinsic mobilities values have also been calculated. From this study, it is found that hole mobility of octyl containing derivative is raised to 4.69 cm(2) V(-1) s(-1). Moreover with attaching octyl group, hole transfer integral values have also been enhanced in newly designed derivatives. The balanced hole and electron reorganization energies, and improved transfer integrals lead to enhanced mobility in derivatives with octyl group, highlighting them as an efficient hole transfer material. Unlike the other electro-optical properties, the intrinsic hole mobility has increased because of transfer integral values of octyl containing derivative C8-DPNDF due to the dense and close crystal packing of C8-DPNDF. However, photostability of furan-based materials has not changed by increasing length of extended alkyl chain. Thus our present investigation highlights the importance of alkyl auxiliary groups that are often neglected/replaced with simple methyl group to save computation costs. Graphical Abstract The hole and electron reorganization energies of naphtho[2,1-b:6,5-b']difuran derivatives.

Design of High-Mobility Diketopyrrolopyrrole-Based π-Conjugated Copolymers for Organic Thin-Film Transistors

Since the report of the first diketopyrrolopyrrole (DPP)-based polymer semiconductor, such polymers have received considerable attention as a promising candidate for high-performance polymer semiconductors in organic thin-film transistors (OTFTs). This Progress Report summarizes the advances in the molecular design of high-mobility DPP-based polymers reported in the last few years, especially focusing on the molecular design of these polymers in respect of tuning the backbone and side chains, and discussing the influences of structural modification of the backbone and side chains on the properties and device performance of corresponding DPP-based polymers. This provides insights for the development of new and high-mobility polymer semiconductors.

Naphtho[1,2b;5,6b′]difuran-based donor–acceptor polymers for high performance organic field-effect transistors

Two naphthodifuran-based donor–acceptor copolymers are presented. Via reasonable main-chain modification and side-chain engineering, remarkably dense π–π stacking spacings (2 V⁻¹ s⁻¹ are achieved at a moderate annealing temperature of 120 °C.

High-performance polymer field-effect transistors fabricated with low-bandgap DPP-based semiconducting materials

New π-conjugated D–A copolymers PDMOTT-n combining a diketopyrrolopyrrole unit and a 3,6-dimethoxythieno[3,2-b]thiophene moiety were synthesized, and their field-effect performances were successfully characterized.