Solution-processable polymers consisting of perylene diimide (PDI) acceptor moieties alternating with dithienothiophene (DTT), N-dodecyl-dithienopyrrole (DTP), or oligomers of these donor groups have been synthesized. We have, in addition to varying the donor, varied the N,N′ substituents of the PDIs. The thermal, optical, electrochemical, and charge-transport properties of the polymers have been investigated. The polymers show broad absorption extending from 300 to 1000 nm with optical band gaps as low as 1.2 eV; the band gap decreases with increasing the conjugation length of donor block, or by replacement of DTT by DTP. The electron affinities of the polymers, estimated from electrochemical data, range from −3.87 to −4.01 eV and are slightly affected by the specific choice of donor moiety, while the estimated ionization potentials (−5.31 to −5.92 eV) are more sensitive to the choice of donor. Bottom-gate top-contact organic field-effect transistors based on the polymers generally exhibit n-channel behavior with electron mobilities as high as 1.7 × 10^–2 cm²/V/s and on/off ratios as high as 10⁶; one PDI-DTP polymer is an ambipolar transport material with electron mobility of 4 × 10^–4 cm²/V/s and hole mobility of 4 × 10^–5 cm²/V/s in air. There is considerable variation in the charge transport properties of the polymers with the chemical structures. © 2013 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2013

A new solution-processable acceptor-acceptor conjugated copolymer (P1) based on perylene diimide (PDI) incorporating planar electron-deficient fluorenone was synthesized by palladium(0)-catalyzed Suzuki coupling reaction. Relative to the donor-acceptor conjugated copolymer (P2) of PDI and dithienothiophene, polymer P1 exhibits 0.1 eV down shift of lowest unoccupied molecular orbital (LUMO) level, 70 nm blue shift of low-energy absorption band, and 0.36 eV increase of optical band gap. Polymer P1 in top-contact bottom-gate organic field-effect transistors exhibits a saturation electron mobility of 0.01 cm²/(V s) in air, while P2 does not function in the same device in air. The better air stability of P1 is attributed to a more dense packing of the polymer chains excluding oxygen or water and lower LUMO level of P1. © 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Organic electron-transporting materials are essential for the fabrication of organic p-n junctions, photovoltaic cells, n-channel field-effect transistors, and complementary logic circuits. Rylene diimides are a robust, versatile class of polycyclic aromatic electron-transport materials with excellent thermal and oxidative stability, high electron affinities, and, in many cases, high electron mobilities; they are, therefore, promising candidates for a variety of organic electronics applications. In this review, recent developments in the area of high-electron-mobility diimides based on rylenes and related aromatic cores, particularly perylene- and naphthalene-diimide-based small molecules and polymers, for application in high-performance organic field-effect transistors and photovoltaic cells are summarized and analyzed.

Two regiochemically defined polythiophenes containing thiazolothiazole acceptor unit were synthesized by palladium(0)-catalyzed Stille coupling reaction. The thermal, electrochemical, optical, charge transport, and photovoltaic properties of these copolymers were examined. Compared to P1 with head-to-head coupling of two middle thiophenes, P2 with head-to-tail coupling of two middle thiophenes exhibits 40 nm red shift of absorption spectrum in film and 0.3 eV higher HOMO level. Both polymers exhibit field-effect hole mobility as high as 0.02 cm² V⁻¹ s⁻¹. Polymer solar cells (PSCs) were fabricated based on the blend of the polymers and methanofullerene[6,6]-phenyl C71-butyric acid methyl ester (PC₇₁BM). The PSC based on P1:PC₇₁BM (1:2, w/w) exhibits a power conversion efficiency of 2.7% under AM 1.5, 100 mW cm⁻², two times of that based on P2:PC₇₁BM. The higher efficiency is attributed to lower HOMO (−5.6 eV) and smaller phase separation scale in P1:PC₇₁BM blend. Tiny change in thiophene connection of P1 and P2 lead to great difference in HOMO, phase separation scale, and efficiency of their photovoltaic devices. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

Soluble conjugated polymers based on 3,5-didecanyldithieno[3,2-b:2′,3′-d]thiophene—single-bond (1), double-bond (2), and triple-bond linked (3)—were synthesized by palladium(0)-catalyzed Stille coupling reaction and oxidation polymerization. The thermal, absorption, emission, and electrochemical properties of these polymers were examined; the effect of the link pattern was studied. All polymers exhibit decomposition temperatures over 295 °C and glass-transition temperatures in the range of 137–202 °C. The absorption spectra of 1, 2, and 3 in thin films exhibit absorption maxima at 381, 584, and 444 nm, respectively. Polymer 1 exhibits intense green emission located at 510 nm in film, whereas polymers 2 and 3 are nonemissive both in solution and in film due to H-aggregate. Cyclic voltammograms of polymers 1, 2, and 3 display irreversible oxidation waves with onset oxidation potentials at 1.73, 0.78, and 1.03 V versus Ag⁺/Ag, respectively. Theory calculation on model compounds suggests that the dihedral angle decreases in the order of 1 > 3 > 2. On reducing the dihedral angle, the polymer exhibits a longer absorption maximum, a smaller bandgap, a less oxidizing potential and fluorescence quench, due to more coplanar and more π-electron delocalized backbone structure. Polymer solar cells were fabricated based on the blend of polymer 2 and methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM). The power conversion efficiency of 0.45% was achieved under AM 1.5, 100 mW cm⁻² using polymer 2:PCBM (1:2, w/w) as active layer. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2843–2852, 2009

A series of low bandgap conjugated polymers consisting of benzothiadiazole alternating with dithienothiophene (DTT) or dithienopyrrole (DTP) unit with or without 3-alkylthiophene bridge have been synthesized. Effect of the fused rings and 3-alkylthiophene bridge on the thermal, optical, electrochemical, charge transport, and photovoltaic properties of these polymers have been investigated. These polymers show broad absorption extending from 300 to 1000 nm with optical bandgaps as low as 1.2 eV; the details of which can be varied either by incorporating 3-alkylthiophene bridge or by replacing DTT with DTP. The LUMO levels (−2.9 to −3.3 eV) are essentially unaffected by the specific choice of donor moiety, whereas the HOMO levels (−4.6 to −5.6 eV) are more sensitive to the choice of donor. The DTT and DTP polymers with 3-alkylthiophene bridge were found to exhibit hole mobilities of 8 × 10⁻⁵ and 3 × 10⁻² cm² V⁻¹ s⁻¹, respectively, in top-contact organic field-effect transistors. Power conversion efficiencies in the range 0.17–0.43% were obtained under simulated AM 1.5, 100 mW cm⁻² irradiation for polymer solar cells using the DTT and DTP-based polymers with 3-alkylthiophene bridge as donor and fullerene derivatives as acceptor. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5498–5508, 2009