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Design and synthesis of low bandgap (LBG) polymer donors is inevitably challenging and their processability from a non-halogenated solvent system remains a hurdle to overcome in the area of high-performance polymer solar cells (PSCs). Due to a high aggregation tendency of LBG polymers, especially diketopyrrolopyrrole (DPP)-based polymers coupled with bithiophenes in the polymer backbones, their widespread adoption in non-halogenated solvent-processed PSCs has been limited. Herein, a novel LBG DPP-based polymer, called PDPP4T-1F with asymmetric arrangement of fluorine atom, has been successfully synthesized and showed an outstanding power conversion efficiency (PCE) of 10.10% in a single-junction fullerene-based PSCs. Furthermore, an impressive PCE of 13.21% has been achieved in a tandem device from a fully non-halogenated solvent system, which integrates a wide bandgap PDTBTBz-2F polymer in the bottom cell and LBG PDPP4T-1F polymer in the top cell. The achieved efficiency is the highest value reported in the literature to date in fullerene-based tandem PSCs. We found that a uniformly distributed interpenetrating fibril network with nano-scale phase separation and anisotropy of the polymer backbone orientation for efficient charge transfer/transport and suppressed charge recombination in PDPP4T-1F-based PSCs led to outstanding PCEs in single and tandem-junction PSCs.

A new wide bandgap (WBG) conjugated polymer diO-PBDB-T containing alkoxy substituted thiophene spacer was designed and synthesized for application as a donor in nonfullerene acceptor (NFA) based po...

In this paper, two cyclohexyl-substituted non-fullerene small molecules, T2-Cy6MRH and T2-Cy6PRH, are designed to have the same molecular backbone of a bithiophene (T2) core and rhodanine (RH) end groups. T2-Cy6MRH and T2-Cy6PRH can be synthesized via two and four synthesis steps, respectively, from commercially available starting materials. Thermogravimetric analysis shows that both small molecules are thermally stable at temperatures greater than 380 °C. Compared with T2-Cy6PRH, T2-Cy6MRH exhibits a higher thermal-transition temperature and a more negative enthalpy change, indicating that it exhibits greater crystallinity. Unlike T2-Cy6MRH, T2-Cy6PRH can form a uniform film via solution-processing, because the introduction of longer flexible alkyl chains endows T2-Cy6PRH with better solubility than T2-Cy6MRH. The T2-Cy6PRH film (λmax = 490 nm) exhibits complementary UV-vis absorption with the small-bandgap polymer donor PTB7-Th (λmax = 700 nm). In addition, the highest occupied molecular orbital and the lowest unoccupied molecular orbital energy levels of T2-Cy6PRH are relatively low-lying compared with those of PTB7-Th. An organic solar cell device based on T2-Cy6PRH and PTB7-Th exhibited a power conversion efficiency (PCE) of 4.60% with a high open-circuit voltage of 1.03 V. The addition of [6,6]-phenyl-C61-butyric acid methyl ester substantially improved the device performance, owing to the improved film morphology and the cascade-energy-level alignment, resulting in a PCE of 6.91% under additive- and annealing-free conditions.

The toxicity of combustion product gas of CR/EPR cables, which are widely used in nuclear power plants, has been investigated according to the aging period. The cable specimens were prepared by thermal acceleration aging method, from non-aged to 40-year-old cables at spans of 10 years. The cable sheath and insulation materials were tested separately. The test was conducted in accordance with the Naval Engineering Standard 713 standard code, which measures the amount of 13 exhaust toxic gases when 1 gram of the test specimen is burnt. The toxicity index and the amount of emission gases were varied irregularly with respect to the aging period, and the reason for this result could not be clearly explained due to the lack of information on cable material. However, the reason could be qualitatively estimated to have two conflicting effects: (1) Reduced flame retardant performance as the devolatilization process proceeded over time, and (2) the enhanced stabilization of double bonds between carbon compounds and flame retardant elements, such as chlorine or bromine, as the cable is aged. The toxicity of the accelerated aging period of 20 years was much higher than that of non-aged cables, which signifies increased probability of fire risks of aged cables from the viewpoint of toxicity. Furthermore, when comparing the adjusted toxicity index calculated without CO, CO2, and NOx emission, it can be clearly determined that the average toxicity index of aged cables is higher than that of non-aged cables. Thus, in conclusion, human hazardousness of a cable fire increases from the viewpoint of toxicity of emission gases as it deteriorates, so safety regulations or maintenance guides for old nuclear power plants should be reinforced considering this toxicity variation. The results obtained from this study can be used to improve the reliability of operator manual actions for safety-shutdown and fire-suppression activities and to provide basic information for studies on fire suppression.

Solution processability is one of the advantages of organic solar cells (OSCs). However, most high-efficiency OSCs are prepared using hazardous chlorinated solvents for the deposition of photoactive layers. The replacement of non-halogenated solvents with eco-friendly green solvents for photoactive materials is urgently required. Herein, we have developed a novel asymmetric T2-OEHRH, which is modified from the symmetric T2-ORH. The introduction of asymmetric alkyl side chains onto rhodanine end groups can effectively suppress excessive self-aggregation/crystallization and substantially improve solubility without sacrificing optoelectrical properties. Therefore, ternary-blend OSCs based on PTB7-Th:EH-IDTBR:T2-OEHRH processed using a non-halogenated solvent system exhibit a uniform and favorable morphology and give a high power conversion efficiency (PCE) of 12.10%. More importantly, we demonstrate an impressive PCE of 9.32% for large-area NFA-OSCs (substrate size = 100 cm2 and aperture size = 55.5 cm2) prepared via D-bar coating in air. To our knowledge, this PCE is the highest reported to date for NFA-based large-area OSC modules processed from a non-halogenated solvent. This asymmetric alkyl-chain engineering strategy can be exploited to develop high-performance large-area NFA-OSCs with eco-friendly solvent processing.

PNTz4T-based polymers have been extensively employed in high-efficiency fullerene-based polymer solar cells (PSCs) with a power conversion efficiency (PCE) of approximately 10.0% due to the high crystallinity of these polymers. The introduction of two fluorine atoms into PNTz4T to synthesize the PNTz4T-2F polymer has boosted the PCE to 10.6%, but the introduction of four fluorine atoms to synthesize the PNTz4T-4F polymer negatively affects the efficiency (PCE = 6.5%), implying that the number of fluorine atoms is not yet optimized. We have developed a new synthetic route for a novel monofluoro-bithiophene monomer and successfully synthesized a novel PNTz4T-1F polymer. The fullerene-based PSCs based on our novel PNTz4T-1F polymer processed using a halogen-free solvent system demonstrated an outstanding PCE of 11.77% (11.67% certified), representing the highest PCE reported thus far in the literature. Due to the optimum molecular ordering/packing, improved interaction with PC71BM and interconnectivity between photoactive material domains, PNTz4T-1F-based PSCs exhibit lower charge carrier recombination and enhanced charge carrier mobility levels, leading to a substantially high photocurrent density (20.37 mA cm−2). These results create new means to tune the structural properties of polymers, ultimately leading to the realization of this class of solar cells for practical applications.

A tissue-like skin-device interface was prepared by using ultrathin functionalized hydrogels for wearable bioelectronics., Hydrogels consist of a cross-linked porous polymer network and water molecules occupying the interspace between the polymer chains. Therefore, hydrogels are soft and moisturized, with mechanical structures and physical properties similar to those of human tissue. Such hydrogels have a potential to turn the microscale gap between wearable devices and human skin into a tissue-like space. Here, we present material and device strategies to form a tissue-like, quasi-solid interface between wearable bioelectronics and human skin. The key material is an ultrathin type of functionalized hydrogel that shows unusual features of high mass-permeability and low impedance. The functionalized hydrogel acted as a liquid electrolyte on the skin and formed an extremely conformal and low-impedance interface for wearable electrochemical biosensors and electrical stimulators. Furthermore, its porous structure and ultrathin thickness facilitated the efficient transport of target molecules through the interface. Therefore, this functionalized hydrogel can maximize the performance of various wearable bioelectronics.

A novel series of benzodithiophene-4,8-dione (BDD)-based copolymers, poly[(4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indacenodithiophene-2,7-diyl)-alt-(1,3-bis(2-ethylhexyl)-5,7-di(thiophene2-yl)benzodithiophene-4,8-dione)] (P1) and poly[(5,5,11,11-tetrakis(4-hexylphenyl)dithieno[2,3-d: 2',3'-d']-s-indacenodithiophene-3,9-diyl)-alt-(1,3-bis(2-ethylhexyl)-5,7-di(thiophene-2-yl)benzodithiophene-4,8-dione)] (P2), which have the same acceptor moiety but different donor segments, have been designed and synthesized for use as donor materials in solution-processable polymer solar cells (PSCs). The optical and photovoltaic properties of the copolymers were investigated. The band gaps of the copolymers were in the range 1.91-1.92 eV. Under optimized conditions, the BDD-based polymers showed power conversion efficiencies (PCEs) for the PSCs in the range 2.52-2.92% under AM 1.5 illumination (100 mW/cm2). Among the copolymers, P1, which contained an indacenodithiophene donor unit, showed a power conversion efficiency of 2.92% with a short circuit current of 7.30 mA/cm2, open circuit voltage of 0.92 V, and a fill factor of 0.43, under AM 1.5 illumination (100 mW/cm2).

The reduction of charge carrier recombination and intrinsic defect density in organic–inorganic halide perovskite absorber materials is a prerequisite to achieving high-performance perovskite solar cells with good efficiency and stability. Here, we fabricated inverted planar perovskite solar cells by incorporation of a small amount of excess organic/inorganic halide (methylammonium iodide (CH3NH3I; MAI), formamidinium iodide (CH(NH2)2I; FAI), and cesium iodide (CsI)) in CH3NH3PbI3 perovskite film. Larger crystalline grains and enhanced crystallinity in CH3NH3PbI3 perovskite films with excess organic/inorganic halide reduce the charge carrier recombination and defect density, leading to enhanced device efficiency (MAI+: 14.49 ± 0.30%, FAI+: 16.22 ± 0.38% and CsI+: 17.52 ± 0.56%) compared to the efficiency of a control MAPbI3 device (MAI: 12.63 ± 0.64%) and device stability. Especially, the incorporation of a small amount of excess CsI in MAPbI3 perovskite film leads to a highly reproducible fill factor of ...

We performed systematic experiments based on a small molecule donor and a polymer acceptor containing a naphthalene diimide (NDI)-based polymer as compared with fullerene-based acceptor (PC71BM) solar cells. Among polymer acceptors, the NDI-based polymer (PNDI-2T) shows good properties such as broad light absorbance with a strong absorption co-efficient and a well oriented crystalline structure leading to high electron mobility. We monitored the photovoltaic properties of both PNDI-2T and PC71BM acceptors with a BDT2TR donor. Although the BDT2TR:PC71BM device showed a higher PCE of 8.20%, the BDT2TR:PNDI-2T device also showed remarkable photovoltaic results with a PCE of 4.43%, VOC of 0.86 V, JSC of 7.26 mA cm−2, and FF of 71% indicating one of the highest efficiencies for small molecule donor and non-fullerene polymer acceptor systems. In particular, the PNDI-2T acceptor showed excellent thermal stability and intrinsic mechanical performance as compared with the PC71BM acceptor. To demonstrate the potential of the polymer acceptor for solar devices, we fabricated a device for testing thermal stability, high thickness tolerance, and the flexibility of the solar cell with bending stress. As a result, the PNDI-2T-based solar cell exhibited excellent thermal stability at 150 °C for 15 h and the PCE of the BDT2TR:PNDI-2T device with a thick active layer (around 610 nm) maintained 80% of its initial value. Moreover, the flexible device with the BDT2TR:PNDI-2T system retained its homogeneous morphology and showed maintained photovoltaic performance even after 100 bending cycles. Therefore, PNDI-2T based organic solar cells have good potential for application as flexible and portable real energy generators.

A series of D–A1–D–A2 type regioregular copolymers based on difluorobenzothiadiazole (DFBT) and dialkoxybenzothiadiazole (ROBT) structures was synthesized. The copolymers were prepared with different alkyl chain lengths and branching point positions. The weaker acceptor, ROBT, was incorporated as a solubilizing moiety, while the stronger acceptor, DFBT, was used to enhance intramolecular charge transfer interactions with low-lying frontier orbital levels. The design of DFBT–ROBT copolymers ensures good planarity via intrachain noncovalent F⋯S, S⋯O, and F⋯H coulombic interactions. Changing the alkyl chain branching point and length had pronounced effects on the interchain packing and charge carrier transport/recombination characteristics of the resultant polymers, which in turn influenced their photovoltaic performances. P2 (with 3-hexylundecyloxy) showed tight π–π stacking, high charge mobility, reduced bimolecular charge recombination, and an optimal nanoscale morphology compared to P1 (with 2-hexyldecyloxy). We prepared photovoltaic devices containing a blend of the copolymers with [6,6]-phenyl-C71-butyric acid methyl ester, and the resultant devices showed high power conversion efficiencies, 8.27% for P2, which is higher than that of P1 (6.87%). Furthermore, the alkyl side-chain length in P2 was varied systematically to study the correlation between the alkyl chain length in the interchain packing and photovoltaic performances. The variation in the alkyl chain branching was effective to modulate intermolecular packing to improve the photovoltaic performances. The optimum side chain length should be determined by carefully considering the solubility and interchain packing interactions.

In Arabidopsis (Arabidopsis thaliana) leaves, starch is synthesized during the day and degraded at night to fuel growth and metabolism. Starch is degraded primarily by β-amylases, liberating maltose, but this activity is preceded by glucan phosphorylation and is accompanied by dephosphorylation. A glucan phosphatase family member, LIKE SEX4 1 (LSF1), binds starch and is required for normal starch degradation, but its exact role is unclear. Here, we show that LSF1 does not dephosphorylate glucans. The recombinant dual specificity phosphatase (DSP) domain of LSF1 had no detectable phosphatase activity. Furthermore, a variant of LSF1 mutated in the catalytic cysteine of the DSP domain complemented the starch-excess phenotype of the lsf1 mutant. By contrast, a variant of LSF1 with mutations in the carbohydrate binding module did not complement lsf1. Thus, glucan binding, but not phosphatase activity, is required for the function of LSF1 in starch degradation. LSF1 interacts with the β-amylases BAM1 and BAM3, and the BAM1-LSF1 complex shows amylolytic but not glucan phosphatase activity. Nighttime maltose levels are reduced in lsf1, and genetic analysis indicated that the starch-excess phenotype of lsf1 is dependent on bam1 and bam3. We propose that LSF1 binds β-amylases at the starch granule surface, thereby promoting starch degradation.

Most non-fullerene acceptors (NFAs) are designed in a complex planar molecular conformation containing fused aromatic rings in high-efficiency organic solar cells (OSCs). To obtain the final molecules, however, numerous synthetic steps are necessary. In this work, a novel simple-structured NFA containing alkoxy-substituted benzothiadiazole and a rhodanine end group (BTDT2R) is designed and synthesized. We also investigate the photovoltaic properties of BTDT2R-based OSCs employing representative polymer donors (wide band gap and high-crystalline P3HT, medium band gap and semicrystalline PPDT2FBT, and narrow band gap and low-crystalline PTB7-Th) to compare the performance capabilities of fullerene acceptor-based OSCs, which are well matched with various polymer donors. OSCs based on P3HT:BTDT2R, PPDT2FBT:BTDT2R, and PTB7-Th:BTDT2R achieved efficiency as high as 5.09, 6.90, and 8.19%, respectively. Importantly, photoactive films incorporating different forms of optical and molecular ordering characteristics exhibit favorable morphologies by means of solvent vapor annealing. This work suggests that the new n-type organic semiconductor developed here is highly promising as a universal NFA that can be paired with various polymer donors with different optical and crystalline properties.

A series of small compound materials based on benzodithiophene (BDT) and diketopyrrolopyrrole (DPP) with three different alkyl side chains were synthesized and used for organic photovoltaics. These small compounds had different alkyl branches (i.e., 2-ethylhexyl (EH), 2-butyloctyl (BO), and 2-hexyldecyl (HD)) attached to DPP units. Thin films made of these compounds were characterized and their solar cell parameters were measured in order to systematically analyze influences of the different side chains of compounds on the film microstructure, molecular packing, and hence, charge-transport and recombination properties. The relatively shorter side chains in the small molecules enabled more ordered packing structures with higher crystallinities, which resulted in higher carrier mobilities and less recombination factors; the small molecule with the EH branches exhibited the best semiconducting properties with a power conversion efficiency of up to 5.54% in solar cell devices. Our study suggested that tuning the alkyl chain length of semiconducting molecules is a powerful strategy for achieving high performance of organic photovoltaics.

Two conjugated polymers based on dithienophosphole oxide, PBDT-O-DTPO and PBDT-T-DTPO, were synthesized. Two polymers were fairly soluble in chlorinated solvents, which is enough for device fabrication. According to the UV–vis spectra of films, PBDT-O-DTPO and PBDT-T-DTPO showed absorption onsets of 656 and 675 nm, correspond to optical band gaps of 1.89 and 1.84 eV, respectively. As the results, two polymers exhibited promising photovoltaic properties with power conversion efficiency (PCE) values of 2.23 and 2.53%, respectively, upon blending with PC71BM under AM 1.5 G illumination.

A series of D–A–D type small molecules containing thiophene and benzo[1,2,5]thiadiazole (BT) as electron-donating and electron-accepting units, respectively, were synthesized using palladium-catalyzed Suzuki coupling reactions. The electron-accepting units of BT were modified with pyridyl nitrogen, a single fluorine atom, or two fluorine atoms to enhance their electron-withdrawing abilities, which resulted in DH5TPys, F-DH5TBs, or 2F-DH5TBs, respectively. The solubilizing hexyl groups were introduced at two different β-positions (3- and 4-positions) on both ends of the thiophene rings. The optical, electrochemical, and photovoltaic properties of the small molecules varied, depending on the introduction of the electron-withdrawing substituents as well as the alkyl variation. The highest occupied molecular orbital (HOMO) energy levels of the small molecules were decreased by the increasing number of fluorine substituents; 4-substitution resulted in deeper HOMO energy levels than 3-substitution. 2F-DH5TB-4 had the lowest HOMO energy level of −5.49 eV. In the organic photovoltaic cells with the configuration ITO/PEDOT:PSS/small molecule:PC71BM/LiF/Al, 2F-DH5TB-4 showed the highest power conversion efficiency (PCE) of 1.11 % owing to the lowest HOMO levels and thus increased the open-circuit voltage. However, two DH5TPys showed low PCEs of 0.20 % despite the deep HOMO energy levels and good UV absorption because of the protonation of pyridyl nitrogen with acidic PEDOT:PSS. In the inverted structure of ITO/ZnO/small molecule:PC71BM/MoO3/Ag, both DH5TPys showed improved PCE values of up to 1.16 %. The device performance of 2F-DH5TB-4 also improved in the inverted structure, showing the PCE of 1.27 %.

A novel thiadiazolo[3,4-c]pyridine] based donor-acceptor (D-A) copolymer, poly[4,8-bis(triisopropylsilylethynyl)benzo[1,2-b:4,5-b']dithiophene-2,6-diyl-alt-[4,7-bis(4-(2-ethylhexyl)thiophen-2-yl)-[1,2,5]thiadiazolo[3,4-c]pyridine] (PTBDTPT), containing triisopropylsilylethynyl(TIPS)benzo[1,2-b:4,5-b']dithiophene as a donor is synthesized by Stille polymerization reaction. All the important photo physical prerequisites for organic field-effect transistor (OFET) application such as strong and broad optical absorption, thermal stability, and compatible HOMO-LUMO levels can be accomplished and combined on one macromolecule. Optical band gap of the polymer was found to be 1.61 eV as calculated from its film onset absorption edge. The hole mobility of bottom gate OFET using the synthesized polymer as an active channel is found to be 1.92 X 10(-2) cm V(-1) s(-1) with the On/Off ratio of 25. The photophysical study suggests that PTBDTPT is promising candidate for future large area organic electronic applications.

Two novel conjugated polymers P1, P2 containing dithienothiadiazole[3,4-c]pyridine acceptor and benzodithiophene, naphthodithiophene donors were synthesized by Stille reaction. The polymers were characterized by 1H NMR, GPC, and elemental analysis. The optical band gaps for P1, P2 were found to be 1.67 and 1.60 eV. The electrochemical studies of P1, P2 revealed the HOMO and LUMO energy levels of the polymer were −5.07, −5.13 eV, and −3.40, −3.53 eV respectively. The polymers are thermally stable up to 380–405 °C. Optoelectronic investigation and electrical properties of fabricated organic field effect transistor (OFET) suggest these polymers can be potential candidates for organic solar cell application.

Two novel polymers containing triple bonds in the backbone with different conjugation types (acceptor–acceptor and acceptor–donor structures) were synthesized and investigated for their crosslinking characteristics under UV irradiation. The crosslink formation was proven via UV-vis and IR spectroscopy, and it was found that the crosslinked polymers have solvent resistance properties during subsequent solvent washing with a similar solvent for the active layer. The two triple bond polymers were used as buffer layer materials to modify the interface properties of electron-selective ZnO in inverted PSCs via a spin-coating process. The effects of the buffer layer on the surface of the ZnO were studied via atomic force microscopy and contact angle measurements. The increased hydrophobic nature of the ZnO surface resulted in better contact with the active layer, and led to an improvement in the performance of the photovoltaic devices with increased fill factor (FF).

We report a systematic study of the role of introduced alkyl chains in the easily synthesized conjugated PDTT-ROBT copolymers, which consist of dithieno[3,2-b:2′,3′-d]thiophene (DTT) and alkoxy substituted benzothiadiazole (ROBT) subunits. We synthesized new conjugated polymers PDTT-BOBT and PDTT-HDBT, which have molecular structures similar to those of the previously reported PDTTDABT polymer, but have modified alkyl chains in the polymer backbone. The modifications of the alkyl chains from linear (PDTTDABT) to branched (PDTT-BOBT and PDTT-HDBT) had prominent effects on the solubility, crystallinity, molecular orientation and morphology of the co-polymers. Solar cell devices containing the new PDTT-BOBT and PDTT-HDBT polymers exhibited power conversion efficiency (PCE) values of 9.2% and 6.2%, respectively, considerably greater than the 2.2% PCE of the previously reported PDTTDABT polymer, and the 9.2% PCE is in fact the highest to date for donor–acceptor polymers containing the BTOR acceptor. This high PCE may be explained by the well-aligned energy levels, optimum film morphology with bicontinuous interpenetrating networks, enhanced charge carrier mobility and decreased amount of charge recombination that we observed for PDTT-BOBT, in contrast to those exhibited by PDTTDABT and PDTT-HDBT. Considering the potential of PDTT-BOBT for industrial application, we tested the scalability, large-area devices (6600 mm2) and stability of PDTT-BOBT. As a result, the PDTT-BOBT polymer with its easily synthesized structure and high efficiency has considerable potential for being synthesized on a large scale and for use in printable electronic applications.

The endosperm is a primary constituent of mature seeds in rice as well as in other cereal crops, serving as the major storage reserve of starch. Observations indicate that the central part of the endosperm is subject to hypoxic conditions, which require a switch of energy metabolism owing to limited mitochondrial respiration. Uniquely, this endosperm generates a large source of inorganic pyrophosphate (PPi) as a byproduct of the reaction of ADP glucose pyrophosphorylase in the cytosol. Recent results derived from examination of the mutants of cereal crops, especially rice, for PPi-utilizing enzymes clearly suggest an important role of PPi as an alternative energy currency for integrating carbon metabolism from sucrose breakdown to starch synthesis in the endosperm. Thus, the present review provides an outline of the interlaced PPi-dependent metabolic pathways, which are critical for starch synthesis in the endosperm in terms of energy metabolism, along with its application to enhance yield potential.

The molecular self-organization of organic semiconductors, which is mainly determined by the structural design, film processing, and device configuration, is one of the crucial factors for achieving high-performance organic photovoltaics (OPVs) and perovskite solar cells (PvSCs). In this study, we newly synthesized and developed strongly self-organized small molecules via alkyl side-chain engineering. Replacing “H” to “C6H13” on the thienyl group, SM2 showed a well-ordered face-on orientation. Due to favorable self-organization leading to effective charge carrier dynamics, including enhanced charge transfer/transport and suppressed recombination, SM2-based OPVs and PvSCs exhibited improved device performance compared to the devices based on SM1 without an additional hexyl side-chain. The best fullerene-based OPV and planar PvSC with SM2 as a small-molecule donor and as a hole transport layer (HTL) achieved an unprecedentedly high efficiency of 9.38% and 20.56%, in contrast with SM1-based devices showing lower efficiency of 8.70% and 15.37%. Furthermore, the planar PvSCs based on undoped-SM2 HTL exhibited comparable efficiency but provided excellent heat and humidity stability compared with doped spiro-OMeTAD-based devices. These results clearly indicated that SM2 with highly-ordered and favorable self-organization is a promising organic semiconductor for future applications of high-performance organic and inorganic-organic hybrid electronics.

A fluorinated BDT-TPD-based donor polymer (P1) was synthesized via Suzuki polymerization. P1 shows a wide bandgap (1.9 eV) and a deep highest occupied molecular orbital level (−5.71 eV). Ternary organic solar cells (OSCs) were fabricated from our synthesized polymer donor (P1) and two small molecular nonfullerene acceptors (IT-4F and Y6). The P1:IT-4F binary OSC exhibited a power conversion efficiency (PCE) of 6.59%, with a short-circuit current density (JSC) of 10.36 mA/cm2, open-circuit voltage (VOC) of 0.91 V and a fill factor (FF) of 70%. By contrast, the P1:Y6 binary OSC exhibited a PCE of 10.58% with a JSC of 22.01 mA/cm2, VOC of 0.86 V and FF of 56%. An enhanced PCE of 11.64% was achieved in the ternary OSC with 25 wt% IT-4F incorporated into the acceptors [IT-4F:Y6 (25:75)]; this enhancement was attributed to the improved JSC of 22.97 mA/cm2, VOC of 0.87 V and FF of 58%. Appropriate phase separation could be achieved by incorporating an appropriate amount of IT-4F into the acceptors, which promoted exciton dissociation and charge transport. The PCE improvement of the IT-4F:Y6 (25:75) ternary device was attributed mainly to enhanced photon harvesting and exciton dissociation and to reduced charge recombination.

RAS proteins play critical roles in various cellular processes, including growth and transformation. RAS proteins are subjected to protein stability regulation via the Wnt/β-catenin pathway, and glycogen synthase kinase 3 beta (GSK3β) is a key player for the phosphorylation-dependent RAS degradation through proteasomes. GSK3β-mediated RAS degradation does not occur in cells that express a nondegradable mutant (MT) β-catenin. Here, we show that β-catenin directly interacts with RAS at the α-interface region that contains the GSK3β phosphorylation sites, threonine 144 and threonine 148 residues. Exposure of these sites by prior β-catenin degradation is required for RAS degradation. The introduction of a peptide that blocks the β-catenin-RAS interaction by binding to β-catenin rescues the GSK3β-mediated RAS degradation in colorectal cancer (CRC) cells that express MT β-catenin. The coregulation of β-catenin and RAS stabilities by the modulation of their interaction provides a mechanism for Wnt/β-catenin and RAS-ERK pathway cross-talk and the synergistic transformation of CRC by both APC and KRAS mutations.

Dithieno[3,2-b:2',3'-d]thiophene (DTT) has emerged as an important building block in the synthesis of a wide variety of optoelectronic materials. Two new DTT containing conjugated polymers, poly(dithieno[3,2-b:2',3'-d]thiophenevinylene-alt-9,9-diethylhexyl-2,7-fluorenediyl vinylene) (FLU-DTT) and poly(dithieno[3,2-b:2',3'-d]thiophenevinylene-alt-2-methoxy-5-(2-ethylhexyloxy)-p-phenylenevinylene) (MEH-DTT), were designed and synthesized. The photoluminescence (PL) spectra of FLU-DTT and MEH-DTT in film exhibit maximum emission peaks at 538 and 602 nm, respectively. The MEH-DTT polymer film showed far more red-shifted maximum electroluminescene (EL) emission at 650 nm. The photovoltaic device was also fabricated using MEH-DTT and PC71BM as active layer and it showed power conversion efficiency (PCE) for the polymer solar cell (PSC) as 0.59% under AM 1.5 G (100 mW/cm2) conditions.

Alfa-amylases are glucan hydrolases that cleave alfa-1,4-glucosidic bonds in starch. In vascular plants,alfa-amylases can be classified into three subfamilies. Arabidopsis has one member of each subfamily. Among them, only AtAMY3 is localized in the chloroplast. We expressed and purified AtAMY3 from Escherichia coli and carried out a biochemical characterization of the protein to find factors that regulate its activity. Recombinant AtAMY3 was active toward both insoluble starch granules and soluble substrates, with a strong preference for alfa-limit dextrin over amylopectin. Activity was shown to be dependent on a conserved aspartic acid residue (Asp666), identified as the catalytic nucleophile in other plant alfa-amylases such as the barley AMY1. AtAMY3 released small linear and branched glucans from Arabidopsis starch granules, and the proportion of branched glucans increased after the predigestion of starch with a beta-amylase. Optimal rates of starch digestion in vitro was achieved when both AtAMY3 and beta-amylase activities were present, suggesting that the two enzymes work synergistically at the granule surface. We also found that AtAMY3 has unique properties among other characterized plant -amylases, with a pH optimum of 7.5– 8, appropriate for activity in the chloroplast stroma. AtAMY3 is also redox-regulated, and the inactive oxidized form of AtAMY3 could be reactivated by reduced thioredoxins. Site-directed mutagenesis combined with mass spectrometry analysis showed that a disulfide bridge between Cys499 and Cys587 is central to this regulation. This work provides new insights into how alfa-amylase activity may be regulated in the chloroplast.

This paper reports on the synthesis and characterization of novel donor-acceptor (D-A) conjugated polymers containing triisopropylsilylethyny(TIPS)benzo[1,2-b:4,5-b']dithiophene-diketopyrrolopyrrole (P1 and P2) through Stille co-polymerization method. Thermal stability, optical and electrochemical properties of these polymers were determined. Optical band gaps of the polymers as calculated from their film onset absorption edges were found to be 1.46 and 1.44 eV, respectively. Electrochemical studies revealed HOMO and LUMO energy levels to be -5.22, -5.60 eV, and -3.76, -4.16 eV, respectively. The polymers were thermally stable up to 400-440 °C. Optoelectronic studies indicated that these materials to be promising candidates in solar cell applications.

Two thieno[3,4-c]pyrrole-4,6-dione (TPD)-based copolymers, poly[5,10-bis(2-ethylhexyloxy) naphtho[1,2-b:5,6-b’]dithiophene-2,7-diyl-alt-1,3-(5-heptadecan-9-yl)-4H-thieno[3,4-c]pyrrole-4,6-dione] (P1) and poly[4,9-bis(2-ethylhexyloxy)naphtho[1,2-b:5,6-b’]dithiophene-2,7-diyl-alt-1,3-(5-heptadecan-9-yl)-4H-thieno[3,4-c]pyrrole-4,6-dione] (P2), were synthesized and used as donor materials in polymer solar cells (PSCs). The optical, electrochemical, and photovoltaic properties of the copolymers were investigated. Under optimized conditions, the TPD-based polymers showed power conversion efficiencies (PCEs) for the PSCs in the range from 1.1 to 2.1% under AM 1.5 illumination (100 mW/cm2).

Two benzo[1,2-b:4,5-b’]dithiophene (BDT)-based copolymers, poly[4,8-bis(5-(2-ethylhexyl) thiophene-2-yl)benzo[1,2-b:4,5-b’]dithiophene-alt-5,8-(2,3-bis(4-octyloxy)phenyl)quinoxaline] (P1) and poly[4,8-bis(5-(2-ethylhexyl)thiophene-2-yl)benzo[1,2-b:4,5-b’]dithiophene-alt-5,7-(2,3-bis(4- octyloxy)phenyl)thieno[3,4-b]pyrazine] (P2), are synthesized and used as donor materials in polymer solar cells (PSCs). To obtain a low band gap polymer, we use a copolymerized donor-acceptor structure. The optical, electrochemical, and photovoltaic properties of the copolymers are investigated. The results indicate that the acceptor units in the copolymers influenced the band gap, electronic energy levels, and photovoltaic properties of the copolymers significantly. The band gaps of the copolymers are in the range 1.34 − 1.75 eV. Under optimized conditions, the BDT-based polymers showed power conversion efficiencies (PCEs) for the PSCs in the range 1.46 − 2.05% under AM 1.5 illumination (100 mW/cm2).

Two donor–acceptor conjugated polymers, PTSSO-TT and PTSSO-BDT, composed of acenaphtho[1,2-c]thiophene-S,S-dioxide (TSSO) as a new electron acceptor and thienothiophene (TT) or benzo[1,2-b:4,5-b']dithiophene (BDT) as electron donors, were synthesized with Stille cross-coupling reactions. The number-averaged molecular weights (Mn) of PTSSO-TT and PTSSO-BDT were found to be 15100 and 26000 Da, with dispersity of 1.8 and 2.4, respectively. The band-gap energies of PTSSO-TT and PTSSO-BDT are 1.56 and 1.59 eV, respectively. The HOMO levels of PTSSO-TT and PTSSO-BDT are −5.4 and −5.5 eV, respectively. These results indicate that the inclusion of TSSO accepting units into polymers is a very effective method for lowering their HOMO energy levels. The field-effect mobilities of PTSSO-TT and PTSSO-BDT were determined to be 1.5 × 10−3 and 4.5 × 10−4 cm2 V−1 s−1, respectively. A polymer solar cell device prepared with PTSSO-TT as the active layer was found to exhibit a power conversion efficiency (PCE) of 3.79% with an open circuit voltage of 0.71 V under AM 1.5 G (100 mW cm−2) conditions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015

ADP-glucose pyrophosphorylase (AGP) catalyzes the first committed step of starch biosynthesis in higher plants. We previously isolated two rice mutants, osagps2 and osagpl2, which have starch-deficient endosperms and lack the AGP small and large subunits, respectively. In this study, we used two-dimensional gel electrophoresis and peptide mass fingerprinting to identify differentially expressed proteins in the osagps2 and osagpl2 endosperms. We found that the osagps2 and osagpl2 endosperms exhibited reduced levels of glutelins and globulins (the major seed storage proteins), protein disulfide isomerases, and the dnaK-type endoplasmic reticulum chaperone BiP. Interestingly, the osagps2 and osagpl2 endosperms had much lower levels of malate dehydrogenase and alanine aminotransferase compared with wild type endosperm, which likely function in maintaining an adequate ATP supply for starch biosynthesis in seed endosperms that are exposed to low oxygen conditions. Furthermore, metabolomics analysis showed that the levels of free amino acids and soluble sugars were significantly increased in the osagps2 and osagpl2 endosperms. These results demonstrate that carbon and nitrogen metabolisms are tightly coordinated to ensure the proper development of rice seed endosperm.

A series of new conjugated polymers based on the asymmetric benzo[1,2-b:4,5-b′]dithiophene (BDT) unit were designed and synthesized for use in bulk-heterojunction polymer solar cells. Each side chain of the BDT was tuned by introducing alkyl and alkoxy groups. The best solar cell efficiency was achieved in an asymmetric polymer device based on 4-octyl-8-octyloxy-BDT (7.64% PCE), which performed better than devices based on the symmetric dioctyl-BDT (6.48% PCE) or dioctyloxy-BDT (7.18% PCE). Further modification of the side chains, replacing octyloxy with butoxydiethoxy, improved the PCE to 8.12% due to the enhanced hole mobility, hole/electron mobility balance, and formation of tight contacts with the PEDOT:PSS layer. The effects of the side chains on the polymer HOMO energy levels and photovoltaic parameters were investigated.

We synthesized and characterized a series of pyrene units incorporated into benzo[1,2-b:4,5-b′]dithiophene-based random copolymers. Concentration-dependent pyrene-driven self-assembly in the copolymers was systematically investigated using measurements of the copolymer optical and electrochemical properties, the hole mobilities extracted from the field-effect transistor and the space charge limited current, and the photovoltaic characteristics. We additionally studied the morphological changes using differential scanning calorimetry (DSC), synchrotron X-ray diffraction analysis, AFM, and TEM. The Py–Py interactions were found to facilitate the formation of fibrous structures. As the Py content increased, multiple Py–Py interactions within a few polymer chains dominated the interchain interactions to produce a more ordered phase but less interconnectivity among many polymer chains. A threshold quantity of the Py moieties enabled the Py–Py interactions to propagate over many polymer chains to form a highly ...

A series of donor-rich semi-random copolymers with various benzodithiophene (donor unit)/fluorinated-thienothiophene (acceptor unit) ratios – D2A, D3A, D5A, D7A – were designed and synthesized for use in polymer solar cells (PSCs). The polymer D1A was also synthesized for comparison. The optical and electrochemical properties of these polymers vary with the number of donor units in their polymer backbones. The device containing the polymer D5A exhibits a best power conversion efficiency (PCE) of 5.52% when the active layer thickness is 340 nm, a value that is 80% of its maximum PCE, whereas the best PCE of the D1A-based device is reduced by 32% when the active layer thickness is 310 nm. A large area (6,270 mm 2 ) D5A-based device prepared with the slot die-coating method was found to exhibit a best PCE of 6.54%, which is significantly better than that of the equivalent D1A-based large area device (4.03%).

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.

New dithieno[3,2-b:2',3'-d]thiophene (DTT)-based copolymers were designed and synthesized for use as donor materials in polymer solar cells (PSCs). The optical, electrochemical, and photovoltaic properties of the copolymers were investigated. The results indicate that the acceptor units in the copolymers influenced the band gap, electronic energy levels, and photovoltaic properties of the copolymers significantly. The band gaps of the copolymers were in the range 1.85-2.02 eV. Under optimized conditions, the DTT-based polymers showed power conversion efficiencies (PCEs) for the PSCs in the range 0.97-1.19% under AM 1.5 illumination (100 mW/cm2). Among the copolymers, P2, which contained a pyrrolo[3,4-f]isoindole-tetraone acceptor unit, showed a power conversion efficiency of 1.19% with a short circuit current of 4.18 mA/cm2, open circuit voltage of 0.77 V, and a fill factor of 0.37, under AM 1.5 illumination (100 mW/cm2).

We isolated a rice (Oryza sativa L.) WRKY gene which is highly upregulated in senescent leaves, denoted OsWRKY42. Analysis of OsWRKY42-GFP expression and its effects on transcriptional activation in maize protoplasts suggested that the OsWRKY42 protein functions as a nuclear transcriptional repressor. OsWRKY42-overexpressing (OsWR KY42OX) transgenic rice plants exhibited an early leaf senescence phenotype with accumulation of the reactive oxygen species (ROS) hydrogen peroxide and a reduced chlorophyll content. Expression analysis of ROS producing and scavenging genes revealed that the metallothionein genes clustered on chromosome 12, especially OsMT1d, were strongly repressed in OsWRKY42OX plants. An OsMT1d promoter:LUC construct was found to be repressed by OsWRKY42 overexpression in rice protoplasts. Finally, chromatin immunoprecipitation analysis demonstrated that OsWRKY42 binds to the W-box of the OsMT1d promoter. Our results thus suggest that OsWRKY42 represses OsMT1d-mediated ROS scavenging and thereby promotes leaf senescence in rice.

Two novel thieno[3,4-b]pyrazine-based copolymers of the donor-acceptor type, poly[4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b’]dithiophene-alt-5,7-(2,3-bis-(4-octyl-oxy-phenyl)-thieno[3,4-b]pyrazine)] (P1) and poly[4,8-bis(5-((2-ethylhexylthiophene)-2-yl))benzo[1,2-b:4,5-b’]dithiophene-alt-5,7-(2,3-bis-(4-octyloxy-phenyl)-thieno[3,4-b]pyrazine)] (P2), designed and synthesized by Stille polymerization for use in polymer solar cells. The synthesis, thermal stability, as well as the optical and photovoltaic properties of these polymers are systematically investigated. The polymers were thermally stable up to 290°C, and readily soluble in common organic solvent. Conventional polymer solar cells (PSCs) with the configuration ITO/PEDOT:PSS/polymer:PC71BM/Ca/Al are fabricated. Under optimized conditions, the polymers display power conversion efficiencies (PCEs) for the PSCs in the range 0.28–1.46% under AM 1.5 illumination. Among the studied thienopyrazine-based copolymers, P2 displays a PCE of 1.46% with a short ...

Donor–acceptor conjugated polymers, PDTTPDA and PDTTPDT, composed of new acenaphtho[1,2-c]thiophene or thiophene as electron donors and 1,3-dithien-2-yl-thieno[3,4-c]pyrrole-4,6-dione (DTTPD) as the electron acceptor were synthesized by a Stille cross-coupling reaction. These polymers combine interesting properties such as good solubility and excellent thermal stability. The weight-averaged molecular weights (Mw) of PDTTPDA and PDTTPDT were found to be 71,000 and 79,000 with polydispersity indices of 1.65 and 1.66, respectively. Photophysical studies revealed a low bandgap of 1.77 eV for PDTTPDA and 1.72 eV for PDTTPDT. The present study indicates that the combination of DTTPD and acenaphtho[1,2-c]thiophene building blocks can be a very effective way to lower the HOMO energy level and ultimately to enhance the Voc of polymer solar cells. The Voc reported here (up to 0.94 V) is one of the highest observed in polymer:PCBM bulk heterojunction devices, and a power conversion efficiency (PCE) of up to 3.28% was observed in the PDTTPDA devices.

A series of novel benzo[1,2-b:4,5-b′]dithiophene (BDT)-based conjugated polymers were synthesized using a Stille cross-coupling reaction. These polymers contained dithienyl thieno[3,4-c]pyrrole-4,6-dione (DTTPD) as an acceptor. Alkylthienylenevinylene thiophene side groups were introduced into the BDT units, and the solubility, absorption spectra, energy levels, charge transport, blend film morphology, and photovoltaic properties of the resulting polymer (poly[4,8-bis{2,2′-(5-ethylhexyl)thienylenevinylenethiophene}benzo[1,2-b;3,4-b]dithiophene-2,6-diyl-alt-1,3-di(thien-5′-yl)-5-octyldodecyl[3,4-c]pyrrole-4,6-dione-2,2′-diyl], PBDTTVT-DTTPD) were investigated. In addition, an alkylthienyl-substituted BDT-based polymer (poly[4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl-alt-1,3-di(thien-5′-yl)-5-octyldodecyl[3,4-c]pyrrole-4,6-dione-2,2′-diyl], PBDTT-DTTPD) was synthesized to compare the optoelectronic and photovoltaic properties of the polymers. The weight-averaged molecular ...

Poly [3,3‴-didodecylquaterselenophene] (PQS) and poly[3,3‴-didodecylquaterselenophene-alt-didodecylquaterthiophene] (PQSQT), have been synthesized by using a Stille cross-coupling reaction. The weight-averaged molecular weights (Mw) of PQS and PQSQT were found to be 18,900 Da and 22,300 Da with polydispersity indices of 1.71 and 1.99, respectively. Photophysical measurements found the low bandgaps of 1.73 eV for PQS and 1.86 eV for PQSQT. The field-effect mobilities of PQS and PQSQT were determined to be 6.0×10−3 and 0.05 cm2/V s, respectively. The influence of the selenium and sulfur atoms in the polymer backbones were investigated with regard to device performances. The polymers were combined with the PC71BM ([6,6]-phenyl C71-butyric acid methyl ester) acceptor to fabricate bulk heterojunction solar cells with power conversion efficiencies of 0.73–2.37% under AM 1.5 G (100 mW/cm2) conditions.

A series of quinoxaline (Qx)-based copolymers, poly[2,7-(9,9-bis(2-ethylhexyl)dibenzosilole)-alt-5,5-(5′,8′-di-2-thienyl-2,3-bis(4-octyloxyl)phenyl)quinoxaline] (P1), poly[4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-alt-5,5-(5′,8′-di-2-thienyl-2,3-bis(4-octyloxyl)phenyl)quinoxaline] (P2), and poly[4,4′-bis(2-ethylhexyl)-dithieno[3,2-b:2′,3′-d]silole-alt-5,5-(5′,8′-di-2-thienyl-2,3-bis(4-octyloxyl)phenyl)quinoxaline] (P3), were synthesized and characterized for use in polymer solar cells (PSCs). We describe the effects of the various donor segments on the optical, electrochemical, field-effect carrier mobilities, and photovoltaic characteristics of the resulting Qx-based copolymers. The results indicated that the donor units in the copolymers significantly influenced the band gap, electronic energy levels, carrier mobilities, and photovoltaic properties of the copolymers. The band gaps of the copolymers were 1.71–2.03 eV. Under optimized conditions, the Qx-based polymers showed power conversion efficiencies for the PSCs of 0.87–2.15% under AM 1.5 illumination (100 mW/cm2). Among the studied Qx-based copolymers, P2, which contained a benzo[1,2-b:4,5-b′]dithiophene unit, showed a power conversion efficiency of 2.15% with a short circuit current of 7.06 mA/cm2, an open-circuit voltage of 0.67 V, and a fill factor of 0.46, under AM 1.5 illumination (100 mW/cm2).

A new donor unit viz. 3,8-bis(2-butyloctyloxy)naphtho[3,2- b :7,6- b ′]dithiophene (NDT) was developed for a novel donor–acceptor semiconducting polymer. And the new NDT-based polymers (PNDTTT-C and PNDTTT-CF) with thienothiophene units were synthesized. The polymers showed deep HOMO levels of −5.44 eV and −5.51 eV with the optical band gap of ∼1.6 eV. The electrochemical as well as optical and photovoltaic properties of these polymers were studied. The OPV devices fabricated from the blends of polymer PNDTTT-C/PNDTTT-CF: PC 71 BM were afforded a high power conversion efficiency of 4.49% and 5.16%, respectively. The optimization of device fabrication included different solvents, different weight ratios and usage of solvent processing additive. To obtain the high PCE a typical processing additive 1,8-diiodooctane was used. The effect of processing additive was studied using AFM analysis. In addition, the field-effect hole mobilities of 3.5×10 −4 cm 2 V −1 s −1 and 5.7×10 −4 cm 2 V −1 s −1 were observed for the polymers PNDTTT-C and PNDTTT-CF, respectively. Since we have developed the synthetic process of the 3,8-bis(2-butyloctyloxy)- naphtho[3,2- b :7,6- b ′]dithiophene(NDT) monomer, the NDT unit will play an important role in future research on conjugated polymer and small molecule design for high-performance organic semiconducting material.

Solution-processable semiconducting copolymers, poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5′-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PCDTBT) and poly[4,8-bis(2-ethylhexyl-2-thenyl)-benzo[1,2-b:4,5-b′]dithiophene-alt-5,5′-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)] (PBDTDTBT), and their pyrene-containing terpolymers were synthesized using Suzuki or Stille coupling. Pyrene units were introduced to improve the charge-transporting abilities of the polymers. The resulting polymers were found to be soluble in common organic solvents and formed smooth and uniform spin-coated thin films. They also exhibited good thermal stability and lost

A novel naphtho[2,3-b:6,7-d′]dithiophene (NDT)-based copolymer, poly[4,9-bis(2-ethylhexyloxy)naphtho[2,3-b:6,7-d′]dithiophene-2,7-diyl-alt-1,3-(5-heptadecan-9-yl)-4H-thieno[3,4-c]pyrrole-4,6-dione] (P1), was synthesized and characterized for use in polymer solar cells. We systematically investigated the synthesis, thermal stability, optical and electrochemical properties, field-effect carrier mobilities, and photovoltaic characteristics of the resulting polymer. The properties of the NDT-based polymer were compared with those of poly[4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b′]dithiophene-alt-1,3-(5-heptadecan-9-yl)-4H-thieno[3,4-c]pyrrole-4,6-dione] (P2) prepared via the same synthetic procedure. Polymer solar cells made from the new polymer, P1, yielded a power conversion efficiency of 4.0% with a short-circuit current density of 11.54 mA/cm2, an open-circuit voltage of 0.69 V, and a fill factor of 0.50 under AM 1.5 G irradiation (100 mW/cm2).

The photovoltaic properties of a series of low band-gap conjugated copolymers, in which alkyl side chains were substituted at various positions, were investigated using donor–acceptor (D–A) conjugated copolymers consisting of a cyclopentadithiophene derivative and dithienyl-benzothiadiazole. The base polymer, which has no alkyl side chains, yielded promising power conversion efficiency of 3.8%. Polymers with alkyl side chains, however, exhibited significantly decreased performance. In addition, the effects of processing additive became negligible. The results indicate that substituted side chains, which were introduced to improve solubility, critically affected the optical and electronic properties of D–A conjugated copolymers. Furthermore, the position of the side chain was also very important for controlling the morphological properties of the D–A conjugated copolymers.

Two new conjugated polymers, PQSS and PQST, were designed and synthesized; these polymers had alkylselenophene-substituted quinoxaline backbones with selenophene and thiophene, respectively, as electron-donating units. The copolymers showed good solubility and film forming abilities, combined with good thermal stability. The number-average molecular weights ( M n ) of PQSS and PQST, determined using gel permeation chromatography (GPC) with a polystyrene standard, were found to be 20,900 ( M w / M n = 1.71) and 22,100 ( M w / M n = 2.41), respectively. The UV–visible absorption maxima of PQSS and PQST were at 617 and 601 nm in solution, and at 682 and 668 nm in the film state. The PQSS and PQST showed low band gaps of 1.50 and 1.52 eV, respectively. Solution-processed field-effect transistors fabricated from these polymers had p-type organic thin film transistor characteristics. The field-effect mobilities of PQSS and PQST were measured to be 1.4 × 10 −4 and 4.8 × 10 −5 cm 2 V −1 s −1 , respectively. The polymers were combined with a PC 71 BM ([6,6]-phenyl C 71 -butyric acid methyl ester) acceptor to fabricate bulk heterojunction solar cells, which produced power conversion efficiencies of 0.40–1.07% under AM 1.5G (100 mW/cm 2 ) conditions.

A series of novel thiophene- and selenophene-based low-bandgap polymers were synthesized using a Stille cross-coupling reaction; these polymers contained quinoxaline and diketopyrrolopyrrole as acceptors. Various acceptors were introduced into the selenophene backbones, and the solubility, absorption spectra, energy levels, charge transport, blend film morphology, and photovoltaic properties of the resulting polymers were investigated. The weight-averaged molecular weights (Mw) of P3TDTQ, P3SDTQ, P3TDTDPP, and P3SDTDPP were found to be 12 300, 15 500, 13 300, and 17 200, with polydispersity indices of 1.46, 1.85, 1.58, and 1.63, respectively. Photophysical studies revealed low bandgaps of 1.70 eV for P3TDTQ, 1.63 eV for P3SDTQ, 1.27 eV for P3TDTDPP, and 1.25 eV for P3SDTDPP; the films could harvest a broad solar spectrum, covering the range from 300 to 800 nm (P3TDTQ and P3SDTQ) and from 350 to 950 nm (P3TDTDPP and P3SDTDPP). Solution-processed field-effect transistors fabricated from these polymers had p...

Three new polymers poly(3,4′′′-didodecyl) hexaselenophene) (P6S), poly(5,5′-bis(4,4′-didodecyl-2,2′-biselenophene-5-yl)-2,2′-biselenophene) (HHP6S), and poly(5,5′-bis(3′,4-didodecyl-2,2′-biselenophene-5-yl)-2,2′-biselenophene) (TTP6S) that have the same selenophene-based polymer backbone but different side chain patterns were designed and synthesized. The weight-averaged molecular weights (Mw) of P6S, HHP6S, and TTP6S were found to be 19,100, 24,100, and 19,700 with polydispersity indices of 2.77, 1.48, and 1.41, respectively. The UV–visible absorption maxima of P6S, HHP6S, and TTP6S are at 524, 489, and 513 nm, respectively, in solution and at 569, 517, and 606 nm, respectively, in the film state. The polymers P6S, HHP6S, and TTP6S exhibit low band gaps of 1.74, 1.95, and 1.58 eV, respectively. The field-effect mobilities of P6S, HHP6S, and TTP6S were measured to be 1.3 × 10−4, 3.9 × 10−6, and 3.2 × 10−4 cm2 V−1 s−1, respectively. A photovoltaic device with a TTP6S/[6,6]-phenyl C71-butyric acid methyl ester (1:3, w/w) blend film active layer was found to exhibit an open circuit voltage (VOC) of 0.71 V, a short circuit current (JSC) of 5.72 mA cm−2, a fill factor of 0.41, and a power conversion efficiency (PCE) of 1.67% under AM 1.5 G (100 mW cm−2) illumination. TTP6S has the most planar backbone of the tested polymers, which results in strong π–π interchain interactions and strong aggregation, leading to broad absorption, high mobility, a low band gap, and the highest PCE. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

A series of quinoxaline-based copolymers, namely, poly[N-9″-heptadecanyl-2,7-carbazole-alt-5,5-(5′,8′-di-2-thienylquinoxaline)] (P1), poly[N-9″-heptadecanyl-2,7-carbazole-alt-5,5-(5′,8′-di-2-thienyl-2,3-bis(4-octyloxyl)phenyl)quinoxaline] (P2), and poly[N-9″-heptadecanyl-2,7-carbazole-alt-5,5-(5′,8′-di-2-thienyl-2,3-bis(4-(3,7-dimethyloctyloxy)phenyl)quinoxaline] (P3), were synthesized and characterized for use in polymer solar cells (PSCs). We describe the effect of modifying the alkyl group of the side chain of the quinoxaline derivatives on the electronic and optoelectronic properties of the polymers. The field-effect hole mobility as well as the electronic energy levels and processability of the materials for PSC applications were investigated. Among the studied quinoxaline-based copolymers, P2 showed the best photovoltaic performance with an open-circuit voltage (VOC) of 0.82 V, a short-circuit current density (JSC) of 9.96 mA/cm2, a fill factor (FF) of 0.49, and a power-conversion efficiency of 4.0%...