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Lee, Jiae,Kim, Jaeyun,Nguyen, Thanh Luan,Kim, Miso,Park, Juhyung,Lee, Yeran,Hwang, Sungu,Kwon, Young-Wan,Kwak, Jeonghun,Woo, Han Young American Chemical Society 2018 Macromolecules Vol.51 No.9
<P>A semicrystalline p-type thermoelectric conjugated polymer based on a polymer backbone of cyclopentadithiophene and benzothiadiazole, poly[(4,4′-(bis(hexyldecylsulfanyl)methylene)cyclopenta[2,1-<I>b</I>:3,4-<I>b</I>′]dithiophene)-<I>alt</I>-(benzo[<I>c</I>][1,2,5]thiadiazole)] (PCPDTSBT), is designed and synthesized by replacing normal alkyl side-chains with bis(alkylsulfanyl)methylene substituents. The sp<SUP>2</SUP>-hybridized olefinic bis(alkylsulfanyl)methylene side-chains and the sulfur-sulfur (S-S) chalcogen interactions extend a chain planarity with strong interchain packing, which is confirmed by density functional calculations and morphological studies, i.e., grazing incidence X-ray scattering measurement. The doping, electrical, morphological, and thermoelectric characteristics of PCPDTSBT are investigated by comparison with those of poly[(4,4′-bis(2-ethylhexyl)cyclopenta[2,1-<I>b</I>:3,4-<I>b</I>′]dithiophene)-<I>alt</I>-(benzo[<I>c</I>][1,2,5]thiadiazole)] (PCPDTBT) with ethylhexyl side-chains. Upon doping with a Lewis acid, B(C<SUB>6</SUB>F<SUB>5</SUB>)<SUB>3</SUB>, the maximum electrical conductivity (7.47 S cm<SUP>-1</SUP>) of PCPDTSBT is ∼1 order higher than that (0.65 S cm<SUP>-1</SUP>) of PCPDTBT, and the best power factor is measured to be 7.73 μW m<SUP>-1</SUP> K<SUP>-2</SUP> for PCPDTSBT with doping 9 mol % of B(C<SUB>6</SUB>F<SUB>5</SUB>)<SUB>3</SUB>. The Seebeck coefficient-electrical conductivity relation is analyzed by using a charge transport model for polymers, suggesting that the doped PCPDTSBT film has superb charge transport property based on a high crystallinity with olefinic side-chains. This study emphasizes the importance of side-chain engineering by using the sp<SUP>2</SUP>-hybridized olefinic substituents to modulate interchain packing, crystalline morphology, and the resulting electrical properties.</P> [FIG OMISSION]</BR>
Lee, Taegon,Hwang, Sungu,Lim, Manho American Chemical Society 2015 The Journal of physical chemistry B Vol.119 No.5
<P>Like nitric oxide (NO), nitroxyl (HNO), a reduced form of NO, plays many biologically important roles including neurological function and vascular regulation. Although HNO is unstable in aqueous solution, it is exceptionally stable on binding to ferrous myoglobin (Mb) to form MbHNO. Various experimental and theoretical investigations has been carried out to unveil the structure of the active site and binding characteristics of MbHNO that can explain its functioning mechanism and the origin of its unusual stability. However, the binding dynamics of HNO to Mb, as well as the photochemical and photophysical processes associated with binding, have not been fully established. Herein, femtosecond vibrational spectroscopy was used to probe the photoexcitation dynamics of excited MbDNO in D<SUB>2</SUB>O solution at 294 K with a 575 nm pulse. Time-resolved spectra were described by three vibrational bands near 1380 cm<SUP>–1</SUP>, in the expected N–O stretching (ν<SUB>N–O</SUB>) mode of MbDNO, and all three bands showed instantaneous bleach that decays on a picosecond time scale. The three bands were assigned based on isotope shifts upon <SUP>15</SUP>N substitution and <I>ab initio</I> calculation of the vibrational frequency on a DNO-bound model heme. These three bands likely arise from Fermi interactions between the strong ν<SUB>N–O</SUB> mode and the weak overtone and combination modes of the N atom-related modes. The immediate appearance of the bleach in these bands and the picosecond decay of the bleach indicate that most of the photoexcited MbDNO undergoes picosecond geminate rebinding (GR) of DNO to Mb subsequent to its immediate deligation. Ultrafast and efficient GR of DNO likely arises from the bonding structure of the ligand and high reactivity between DNO and Mb.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcbfk/2015/jpcbfk.2015.119.issue-5/jp509644m/production/images/medium/jp-2014-09644m_0006.gif'></P>
Lee, Wonho,Cha, Hyojung,Kim, Yu Jin,Jeong, Ji-Eun,Hwang, Sungu,Park, Chan Eon,Woo, Han Young American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.22
<P>Three types of amorphous thienothiophene (TT)-benzothiadiazole (BT) based copolymers (<B>PFTTBT</B>) were synthesized by incorporating alkyl-substituted fluorene moieties as a third component in the polymer backbone. Their optical, electrochemical, morphological, and photovoltaic properties were examined by a comparison with those of a crystalline TT-BT derivative (<B>PTTBT14</B>). <B>PTTBT14</B> was reported to have a high hole mobility (0.26 cm<SUP>2</SUP>/(V s)) due to the pronounced interchain ordering but poor photovoltaic power conversion efficiency (PCE) of 2.4–2.6% was reported due to excessively strong self-interactions with poor miscibility with fullerene structures. By incorporating fluorene units, the UV–vis spectra showed an increased bandgap (∼1.9 eV) with the disappearance of the packing-originated shoulder peak, and the valence band decreased compared to crystalline <B>PTTBT14</B>. The amorphous <B>PFTTBT</B> polymers showed substantially improved photovoltaic properties compared to <B>PTTBT14</B>, even though they showed poor hole mobility (∼10<SUP>–6</SUP> cm<SUP>2</SUP>/(V s)) and fill factor. The optimal devices were achieved by blending with excess PC<SUB>71</SUB>BM (polymer:PC<SUB>71</SUB>BM = 1:4 by weight), showing little improvement in the thermal and additive treatments. Under simulated solar illumination of AM 1.5 G, the best PCE of 6.6% was achieved for a <B>PFehTTBT</B>:PC<SUB>71</SUB>BM device with an open-circuit voltage of 0.92 V, a short-circuit current of 15.1 mA/cm<SUP>2</SUP>, and a fill factor of 0.48. These results suggest that it is useful to disrupt partially the interchain organizations of excessively crystalline polymers, enabling fine-control of intermolecular ordering and the morphological properties (i.e., miscibility with fullerene derivatives, etc.) to utilize the advantages of both crystalline and amorphous materials for further improving PCE of polymer solar cells.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-22/am5061189/production/images/medium/am-2014-061189_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5061189'>ACS Electronic Supporting Info</A></P>