Immobilization of cytochrome c on beaded poly(N-acrylylpyrrolidine)

In order to examine a procedure whereby the points of covalent attachment between the components of a protein-polymer conjugate could be determined, horse heart cytochrome c was attached to a beaded copolymer of N-acrylylpyrrolidine, N,N′-bis(acrylyl)-1,2-diaminoethane and N-acrylyl-1,6-aminohexane through a cleavable azo linkage. Studies of protein removed from this conjugate showed that attachment of the polymer to cytochrome occurred predominantly through single lysine residues on the protein surface; lysine-25 was tentatively identified as the residue most extensively utilized in this way. Protein was also linked to the polymer by two lysine residues and a significant amount of protein was irreversibly attached to the polymer under the reaction conditions used.     

Extermination Speed of an Imidacloprid and Flumethrin Polymer Matrix Collar against Larvae,Nymphs and Adults of Haemaphysalis longicornis

The objective of this study was to evaluate the efficacy of an imidacloprid 10% and flumethrin 4.5% polymer matrix collar against the developmental stages of Haemaphysalis longicornis infesting dogs using the hair from treated dogs in a semi-in-vitro assay set. When incubated with 0.5 g of the hair collected from the dogs installed with the drug-embedded collar after 10 days, average death rate of the larval, nymphal, and adult H. longicornis was 21.5%, 77.9%, and 100% at 30 min, 1 hr, and 2 hr, respectively. This study showed the larval stages as well as the nymphal and adult stages of H. longicornis ticks are killed upon contact with the hair from dogs treated with the collar within 2 hr.     

Electrohydrodynamic instabilities and segregation of polysaccharides in capillary polymer solution electrophoresis

During capillary electrophoresis of negatively charged polysaccharides in polymer solutions as sieving media, concentration fluctuations develop due to electrohydrodynamic instabilities caused by polarization of the polyelectrolytic chains. This leads to deviations from electroneutrality far beyond the Debye layer and segregation of the initially homogeneous sample solution into aggregated sample‐rich domains as verified by epifluorescence videomicroscopy imaging. As a result, anomalous and irregular peak profiles are obtained impeding the characterization of such complex sample mixtures. This effect appears at an electric field strength threshold value that depends on the molecular weight of the solute polymer molecules, pH, type and concentration of the polymer solution sieving media, and buffering conditions. The magnitude increases with increasing field strength and amount of sample injected. The aggregation onset, as evaluated by the value of the threshold potential, is affected by the charge density of the sample polymer molecules and Debye screening effects and investigated through variation of pH and ionic strength, respectively. Exchange of a simple base buffer component for small and multiply charged organic bases markedly increases the electric field strength necessary to trigger the electrohydrodynamic instabilities. Ultimately, the threshold value could be increased more than seven times by addition of an oppositely charged aminodextran polymer, thereby decreasing the analysis time. © 1999 John Wiley & Sons, Inc. Biopoly 49: 515–524, 1999     

High‐Performance and Stable All‐Polymer Solar Cells Using Donor and Acceptor Polymers with Complementary Absorption

To explore the advantages of emerging all‐polymer solar cells (all‐PSCs), growing efforts have been devoted to developing matched donor and acceptor polymers to outperform fullerene‐based PSCs. In this work, a detailed characterization and comparison of all‐PSCs using a set of donor and acceptor polymers with both conventional and inverted device structures is performed. A simple method to quantify the actual composition and light harvesting contributions from the individual donor and acceptor is described. Detailed study on the exciton dissociation and charge recombination is carried out by a set of measurements to understand the photocurrent loss. It is unraveled that fine‐tuned crystallinity of the acceptor, matched donor and acceptor with complementary absorption and desired energy levels, and device architecture engineering can synergistically boost the performance of all‐PSCs. As expected, the PBDTTS‐FTAZ:PNDI‐T10 all‐PSC attains a high and stable power conversion efficiency of 6.9% without obvious efficiency decay in 60 d. This work demonstrates that PNDI‐T10 can be a potential alternative acceptor polymer to the widely used acceptor N2200 for high‐performance and stable all‐PSCs.     

Thieno[3,4‐c]Pyrrole‐4,6‐Dione‐Based Polymer Acceptors for High Open‐Circuit Voltage All‐Polymer Solar Cells

While polymer acceptors are promising fullerene alternatives in the fabrication of efficient bulk heterojunction (BHJ) solar cells, the range of efficient material systems relevant to the “all‐polymer” BHJ concept remains narrow, and currently limits the perspectives to meet the 10% efficiency threshold in all‐polymer solar cells. This report examines two polymer acceptor analogs composed of thieno[3,4‐c ]pyrrole‐4,6‐dione (TPD) and 3,4‐difluorothiophene ([2F]T) motifs, and their BHJ solar cell performance pattern with a low‐bandgap polymer donor commonly used with fullerenes (PBDT‐TS1; taken as a model system). In this material set, the introduction of a third electron‐deficient motif, namely 2,1,3‐benzothiadiazole (BT), is shown to (i) significantly narrow the optical gap (E _opt) of the corresponding polymer (by ≈0.2 eV) and (ii) improve the electron mobility of the polymer by over two orders of magnitude in BHJ solar cells. In turn, the narrow‐gap P2TPDBT[2F]T analog (E _opt = 1.7 eV) used as fullerene alternative yields high open‐circuit voltages (V _OC) of ≈1.0 V, notable short‐circuit current values (J _SC) of ≈11.0 mA cm⁻², and power conversion efficiencies (PCEs) nearing 5% in all‐polymer BHJ solar cells. P2TPDBT[2F]T paves the way to a new, promising class of polymer acceptor candidates.     

Thiophene Rings Improve the Device Performance of Conjugated Polymers in Polymer Solar Cells with Thick Active Layers

Developing novel materials that tolerate thickness variations of the active layer is critical to further enhance the efficiency of polymer solar cells and enable large‐scale manufacturing. Presently, only a few polymers afford high efficiencies at active layer thickness exceeding 200 nm and molecular design guidelines for developing successful materials are lacking. It is thus highly desirable to identify structural factors that determine the performance of semiconducting conjugated polymers in thick‐film polymer solar cells. Here, it is demonstrated that thiophene rings, introduced in the backbone of alternating donor–acceptor type conjugated polymers, enhance the fill factor and overall efficiency for thick (>200 nm) solar cells. For a series of fluorinated semiconducting polymers derived from electron‐rich benzo[1,2‐b:4,5‐b′]dithiophene units and electron‐deficient 5,6‐difluorobenzo[2,1,3]thiazole units a steady increase of the fill factor and power conversion efficiency is found when introducing thiophene rings between the donor and acceptor units. The increased performance is a synergistic result of an enhanced hole mobility and a suppressed bimolecular charge recombination, which is attributed to more favorable polymer chain packing and finer phase separation.     

Improved Performance of Ternary Polymer Solar Cells Based on A Nonfullerene Electron Cascade Acceptor

Efficient ternary polymer solar cells are constructed by incorporating an electron‐deficient chromophore (5Z,5′Z)‐5,5′‐((7,7′‐(4,4,9,9‐tetrakis(4‐hexylphenyl)‐4,9‐dihydro‐s‐indaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis(6‐fluorobenzo[c][1,2,5]thiadiazole‐7,4‐diyl))bis(methanylylidene))bis(3‐ethyl‐2‐thioxothiazolidin‐4‐one) (IFBR) as an additional component into the bulk‐heterojunction film that consists of a wide‐bandgap conjugated benzodithiophene‐alt‐difluorobenzo[1,2,3]triazole based copolymer and a fullerene acceptor. With respect to the binary blend films, the incorporation of a certain amount of IFBR leads to simultaneously enhanced absorption coefficient, obviously extended absorption band, and improved open‐circuit voltage. Of particular interest is that devices based on ternary blend film exhibit much higher short‐circuit current densities than the binary counterparts, which can be attributed to the extended absorption profiles, enhanced absorption coefficient, favorable film morphology, as well as formation of cascade energy level alignment that is favorable for charge transfer. Further investigation indicates that the ternary blend device exhibits much shorter charge carrier extraction time, obviously reduced trap density and suppressed trap‐assisted recombination, which is favorable for achieving high short‐circuit current. The combination of these beneficial aspects leads to a significantly improved power conversion efficiency of 8.11% for the ternary device, which is much higher than those obtained from the binary counterparts. These findings demonstrate that IFBR can be a promising electron‐accepting material for the construction of ternary blend films toward high‐performance polymer solar cells.     

Self‐Doped,n‐Type Perylene Diimide Derivatives as Electron Transporting Layers for High‐Efficiency Polymer Solar Cells

Perylene diimide (PDI) with high electron affinities are promising candidates for applications in polymer solar cells (PSCs). In addition, the strength of π‐deficient backbones and end‐groups in an n‐type self‐dopable system strongly affects the formed end‐group‐induced electronic interactions. Herein, a series of amine/ammonium functionalized PDIs with excellent alcohol solubility are synthesized and employed as electron transporting layers (ETLs) in PSCs. The electron transfer properties of the resulting PDIs are dramatically tuned by different end‐groups and π‐deficient backbones. Notably, electron transfer is observed directly in solution in self‐doped PDIs for the first time. A significantly enhanced power conversion efficiency of 10.06% is achieved, when applying the PDIs as ETLs in PTB7‐Th:PC₇₁BM‐based PSCs. These results demonstrate the potential of n‐type organic semiconductors with stable n‐type doping capability and facile solution processibility for future applications of energy transition devices.     

Effect of Molecular Orientation of Donor Polymers on Charge Generation and Photovoltaic Properties in Bulk Heterojunction All‐Polymer Solar Cells

All‐polymer solar cells (all‐PSCs) utilizing p‐type polymers as electron‐donors and n ‐typepolymers as electron‐acceptors have attracted a great deal of attention, and their efficiencies have been improved considerably. Here, five polymer donors with different molecular orientations are synthesized by random copolymerization of 5‐fluoro‐2,1,3‐benzothiadiazole with different relative amounts of 2,2′‐bithiophene (2T) and dithieno[3,2‐b;2′,3′‐d]thiophene (DTT). Solar cells are prepared by blending the polymer donors with a naphthalene diimide‐based polymer acceptor (PNDI) or a [6,6]‐phenyl C₇₁‐butyric acid methyl ester (PC₇₁BM) acceptor and their morphologies and crystallinity as well as optoelectronic, charge‐transport and photovoltaic properties are studied. Interestingly, charge generation in the solar cells is found to show higher dependence on the crystal orientation of the donor polymer for the PNDI‐based all‐PSCs than for the conventional PC₇₁BM‐based PSCs. As the population of face‐on‐oriented crystallites of the donor increased in PNDI‐based PSC, the short‐circuit current density (J_SC) and external quantum efficiency of the devices are found to significantly improve. Consequently, device efficiency was enhanced of all‐PSC from 3.11% to 6.01%. The study reveals that producing the same crystal orientation between the polymer donor and acceptor (face‐on/face‐on) is important in all‐PSCs because they provide efficient charge transfer at the donor/acceptor interface.