In this report, four donor–acceptor copolymers, P(NDT3-BT), P(NDT3-BO), P(NDF3-BT), and P(NDF3-BO), using 5,10-didodecyl-naphtho[1,2-b:5,6-b′]dithiophene (NDT3) or 5,10-didodecyl-naphtho[1,2-b:5,6-b′]difuran (NDF3) as an electron-rich unit and benzodiathiazole (BT) or benzoxadiazole (BO) as an electron-deficient one, were designed, synthesized, and characterized. Detailed systematical investigation was developed for studying the effect of the S/O atoms on the optical, electrochemical, and morphological properties of the polymers, as well as the subsequent performance of the organic field-effect transistors (OFETs) fabricated from these copolymers. It was found that, compared with NDF3-based P(NDF3-BT)/P(NDF3-BO), by replacing NDF3 with stronger aromatic NDT3, the resultant P(NDT3-BT)/P(NDT3-BO) show smaller lamellar distance with an increased surface roughness in solid state, and relatively higher hole mobilities are obtained. The hole mobilities of the four polymers based on OFETs varied from 0.20 to 0.32 cm² V⁻¹ s⁻¹ depending on their molecular structures, giving some valuable insights for the further design and development of a new generation of semiconducting materials. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014, 52, 2465–2476

A series of novel poly(thienylene vinylene) derivatives (PTVs), P20-P24, with imide substituents were designed and synthesized by palladium-catalyzed Stille coupling polymerization, wherein the imide substituent density was decreased gradually, which allowed us to explicitly study the effect of electron-deficient substituent on the optical, electrochemical, and photovoltaic properties of the PTVs. All of the four polymers showed broad absorption bands with optical bandgaps between1.66 and 1.78 eV. By reducing density of electron-deficient imide group, the LUMO energy levels of the polymers could be tuned gradually from −3.75 to −3.43 eV, with HOMO levels upshifted from −5.64 to −5.16 eV. Bulk heterojunction solar cells with the polymers as donor and PC₇₁BM as acceptor demonstrated very different excitons dissociation behavior. With decreasing the imide-fused unit density, the open-circuit voltage (V_OC) values in the devices decreased from 0.78 to 0.62 V, whereas the short-circuit currents (J_SC) increased from 0 to 2.26 mA cm⁻² and then decreased to 1.01 mA cm⁻². By adjusting the electron-withdrawing imide substituent density, power conversion efficiency of the PTVs-based solar cells can be increased to four times, reached 0.86%. To the best of our knowledge, this is the first systematic study of the relationship between molecular energy level and photovoltaic properties of PTVs. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4975–4982

Two novel porphyrin-based D-A conjugated copolymers, PFTTQP and PBDTTTQP, consisting of accepting quinoxalino[2,3-b′]porphyrin unit and donating fluorene or benzo[1,2-b:4,5-b′]dithiophene unit, were synthesized, respectively via a Pd-catalyzed Stille-coupling method. The quinoxalino[2,3-b′]porphyrin, an edge-fused porphyrin monomer, was used as a building block of D-A copolymers, rather than the simple porphyrin unit in conventional porphyrin-based photovoltaic polymers reported in literature, to enhance the coplanarity and to extend the π-conjugated system of polymer main chains, and consequently to facilitate the intramolecular charge transfer (ICT). The thermal stability, optical, and electrochemical properties as well as the photovoltaic characteristics of the two polymers were systematically investigated. Both the polymers showed high hole mobility, reaching 4.3 × 10⁻⁴ cm² V⁻¹ s⁻¹ for PFTTQP and 2.0 × 10⁻⁴ cm² V⁻¹ s⁻¹ for PBDTTTQP. Polymer solar cells (PSCs) made from PFTTQP and PBDTTTQP demonstrated power conversion efficiencies (PCEs) of 2.39% and 1.53%, both of which are among the highest PCE values in the PSCs based on porphyrin-based conjugated polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013

A novel fused ladder alternating D–A copolymer, PIDT–DPP, with alkyl substituted indacenodithiophene (IDT) as donor unit and diketopyrrolopyrrole (DPP) as acceptor unit, was designed and synthesized by Pd-catalyzed Stille-coupling method. The copolymer showed good solubility and film-forming ability combining with good thermal stability. PIDT–DPP exhibited a broad absorption band from 350 to 900 nm with an absorption peak centered at 735 nm. The optical band gap determined from the onset of absorption of the polymer film was 1.37 eV. The highest occupied molecular orbital level of the polymer is as deep as −5.32 eV. The solution-processed organic field-effect transistor (OFETs) was fabricated with bottom gate/top contact geometry. The highest FET hole mobility of PIDT–DPP reached 0.065 cm² V⁻¹ s⁻¹ with an on/off ratio of 4.6 × 10⁵. This mobility is one of the highest values for narrow band gap conjugated polymers. The power conversion efficiency of the polymer solar cell based on the polymer as donor was 1.76% with a high open circuit voltage of 0.88 V. To the best of our knowledge, this is the first report on the photovoltaic properties of alkyl substituted IDT-based polymers. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2012

Photovoltaic performance of polymer solar cells based on poly(3-hexylthiophene) (P3HT) as the donor and indene-C₇₀ bisadduct (IC₇₀BA) as the acceptor is improved by adding 3 vol% 3-methylthiophene (MT) or 3-hexylthiophene (HT) as processing additives. The results of UV-vis absorption spectroscopy, X-ray diffraction analysis and atomic force microscopy indicate that with the MT or HT processing additive, the active layer of the blend of P3HT/IC₇₀BA showed strengthened absorbance, enhanced crystallinity and improved film morphology. The power conversion efficiency (PCE) of the PSCs was improved from 5.80% for the device without the additive to 6.35% for the device with HT additive and to 6.69% with MT additive. The PCE of 6.69% is the top value reported so far for the PSCs based on P3HT.

Via A₂ + B₄ and A₂ + B₃ [where A₂ is 1,4-distyrylol-2,5-butoxybenzene, B₃ is 1,1,1-tris-(p-tosyloxymethyl)-propane, and B₄ is pentaerythritol tetra(methyl benzene sulfonate)] approaches, we synthesized two kinds of partially conjugated hyperbranched polymers, hyperbranched polymer with 3 arms (HP1) and hyperbranched polymer with 4 arms (HP2), which had rigid conjugated segments [oligo-poly(phenylene vinylene)] and flexible, nonconjugated spacers arranged alternately through ether bonds in the skeleton. The conjugated segments were modified by pendant butoxy groups, which imparted the resulting polymers with excellent solubility in common organic solvents and excellent film-forming abilities. Fourier transform infrared and nuclear magnetic resonance spectroscopy were used to identify the structure of the monomers and polymers. Thermal property investigations showed that two polymers both had good thermal stability with their decomposition temperatures in the range 396–405°C and high glass-transition temperatures, which are of benefit to the fabrication of high-performance light-emitting devices. The photophysical properties were studied, and the relative photoluminescence quantum efficiencies of HP1 and HP2 in dilute chloroform solution amounted to 56.8 and 49.3%, respectively. A brief light-emitting diode device with a configuration of indium tin oxide/HP1/Ca/Al was fabricated, and its electroluminescence performance was studied. The brightness of the device reached an optimistic maximum of 190 cd/m² at 8.2 V. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010