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Kim, Jonggi,Yun, Myoung Hee,Kim, Gi-Hwan,Lee, Jungho,Lee, Sang Myeon,Ko, Seo-Jin,Kim, Yiho,Dutta, Gitish K.,Moon, Mijin,Park, Song Yi,Kim, Dong Suk,Kim, Jin Young,Yang, Changduk American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.10
<P>The introduction of fluorine (F) atoms onto conjugated polymer backbone has verified to be an effective way to enhance the overall performance of polymer-based bulk-heterojunction (BHJ) solar cells, but the underlying working principles are not yet fully uncovered. As our attempt to further understand the impact of F, herein we have reported two novel fluorinated analogues of PCDTBT, namely, <B>PCDTFBT</B> (1F) and <B>PCDT2FBT</B> (2F), through inclusion of either one or two F atoms into the benzothiadiazole (BT) unit of the polymer backbone and the characterization of their physical properties, especially their performance in solar cells. Together with a profound effect of fluorination on the optical property, nature of charge transport, and molecular organization, F atoms are effective in lowering both the HOMO and LUMO levels of the polymers without a large change in the energy bandgaps. <B>PCDTFBT</B>-based BHJ solar cell shows a power conversion efficiency (PCE) of 3.96 % with high open-circuit voltage (<I>V</I><SUB>OC</SUB>) of 0.95 V, mainly due to the deep HOMO level (−5.54 eV). To the best of our knowledge, the resulting <I>V</I><SUB>OC</SUB> is comparable to the record <I>V</I><SUB>OC</SUB> values in single junction devices. Furthermore, to our delight, the best <B>PCDTFBT</B>-based device, prepared using 2 % v/v diphenyl ether (DPE) additive, reaches the PCE of 4.29 %. On the other hand, doubly-fluorinated polymer <B>PCDT2FBT</B> shows the only moderate PCE of 2.07 % with a decrease in <I>V</I><SUB>OC</SUB> (0.88 V), in spite of the further lowering of the HOMO level (−5.67 eV) with raising the number of F atoms. Thus, our results highlight that an improvement in efficiency by tuning the energy levels of the polymers by means of molecular design can be expected only if their truly optimized morphologies with fullerene in BHJ systems are materialized.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-10/am500891z/production/images/medium/am-2014-00891z_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am500891z'>ACS Electronic Supporting Info</A></P>
Kim, Gi-Ae,Lim, Young-Suk,Han, Seungbong,Choi, Jonggi,Shim, Ju Hyun,Kim, Kang Mo,Lee, Han Chu,Lee, Yung Sang BMJ 2018 Gut Vol.67 No.5
<B>Objective</B><P>High serum HBV DNA levels are associated with high risks of hepatocellular carcinoma (HCC) and cirrhosis in patients with chronic hepatitis B (CHB). Although the immune-tolerant (IT) phase is characterised by high circulating HBV DNA levels, it remains unknown whether antiviral treatment reduces risks of HCC and mortality.</P><B>Design</B><P>This historical cohort study included HBeAg-positive patients with CHB with high HBV DNA levels (≥20 000 IU/mL) and no evidence of cirrhosis at a tertiary referral hospital in Korea from 2000 to 2013. The clinical outcomes of 413 untreated IT-phase patients with normal alanine aminotransferase (ALT) levels (females, <19 IU/mL; males, <30 IU/mL) were compared with those of 1497 immune-active (IA)-phase patients (ALT ≥80 IU/mL) treated with nucleos(t)ide analogues.</P><B>Results</B><P>The IT group was significantly younger than the IA group (mean age, 38 vs 40 years at baseline, p=0.04). The 10-year estimated cumulative incidences of HCC (12.7% vs 6.1%; p=0.001) and death/transplantation (9.7% vs 3.4%; p<0.001) were significantly higher in the IT group than the IA group. In multivariable analyses, the IT group showed a significantly higher risk of HCC (HR 2.54; 95% CI 1.54 to 4.18) and death/transplantation (HR 3.38; 95% CI 1.85 to 6.16) than the IA group, which was consistently identified through inverse probability treatment weighting, propensity score-matched and competing risks analyses.</P><B>Conclusions</B><P>Untreated IT-phase patients with CHB had higher risks of HCC and death/transplantation than treated IA-phase patients. Unnecessary deaths could be prevented through earlier antiviral intervention in select IT-phase patients.</P>
Kim, Jonggi,Yun, Myoung Hee,Lee, Junghoon,Kim, Jin Young,Wudl, Fred,Yang, Changduk Royal Society of Chemistry 2011 Chemical communications Vol.47 No.11
<P>Through the esterification of an acyl chloride functionalized fullerene precursor with dendritic alcohol, a fullerene-rich dendron containing a norbornene unit at the focal point is prepared for ring-opening metathesis polymerization to obtain its linear polymer with a unimodal and narrow molar mass distribution (PDI = 1.08) by a progressive addition of catalysts.</P> <P>Graphic Abstract</P><P>A platform for a fullerene-rich linear polymer is established through ROMP and a controlled methodology of addition of catalyst. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0cc05470d'> </P>
Kim, Jonggi,Han, A-Reum,Seo, Jung Hwa,Oh, Joon Hak,Yang, Changduk American Chemical Society 2012 Chemistry of materials Vol.24 No.17
<P>A novel highly π-extended heteroacene with four symmetrically fused thiophene-ring units and solubilizing substituents at the terminal β-positions on the central ring, dithieno[2,3-<I>d</I>;2′,3′<I>-d</I>′]benzo[1,2-<I>b</I>;4,5-<I>b</I>′]dithiophene (DTBDT) was synthesized via intramolecular electrophilic coupling reaction. The α-positions availability in the DTBDT motif enables the preparation of solution-processable DTBDT-based polymers such as <B>PDTBDT</B>, <B>PDTBDT-BT</B>, <B>PDTBDT-DTBT</B>, and <B>PDTBDT-DTDPP</B>. Even with its highly extended acene-like π-framework, all polymers show fairly good environmental stability of their highest occupied molecular orbitals (HOMOs) from −5.21 to −5.59 eV. In the course of our study to assess a profile of semiconductor properties, field-effect transistor performance of the four DTBDT-containing copolymers via solution-process is characterized, and <B>PDTBDT-DTDPP</B> exhibits the best electrical performance with a hole mobility of 1.70 × 10<SUP>–2</SUP> cm<SUP>2</SUP> V<SUP>–1</SUP> s<SUP>–1</SUP>. <B>PDTBDT-DTDPP</B> has a relatively smaller charge injection barrier for a hole from the gold electrodes and maintains good coplanarity of the polymer backbone, indicating the enhanced π–π stacking characteristic and charge carrier transport. The experimental results demonstrate that our molecular design strategy for air-stable, high-performance organic semiconductors is highly promising.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2012/cmatex.2012.24.issue-17/cm301816t/production/images/medium/cm-2012-01816t_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm301816t'>ACS Electronic Supporting Info</A></P>
Kim, Jonggi,Han, A-Reum,Hong, Jayeon,Kim, Gyoungsik,Lee, Junghoon,Shin, Tae Joo,Oh, Joon Hak,Yang, Changduk American Chemical Society 2014 Chemistry of materials Vol.26 No.17
<P>Recognizing the importance of molecular coplanarity and with the aim of developing new, ideal strong acceptor-building units in semiconducting polymers for high-performance organic electronics, herein we present a simplified single-step synthesis of novel vinylene- and acetylene-linked bis-benzothiadiazole (<B>VBBT</B> and <B>ABBT</B>) monomers with enlarged planarity relative to a conventionally used acceptor, benzothiadiazole (BT). Along these lines, four polymers (<B>PDPP-VBBT</B>, <B>PDPP-ABBT</B>, <B>PIID-VBBT</B>, and <B>PIID-ABBT</B>) incorporating either <B>VBBT</B> or <B>ABBT</B> moieties are synthesized by copolymerizing with centro-symmetric ketopyrrole cores, such as diketopyrrolopyrrole (DPP) and isoindigo (IID), and their electronic, physical, and transistor properties are studied. These polymers show relatively balanced ambipolar transport, and <B>PDPP-VBBT</B> yields hole and electron mobilities as high as 0.32 and 0.13 cm<SUP>2</SUP> V<SUP>–1</SUP> s<SUP>–1</SUP>, respectively. Interestingly, the acetylenic linkages lead to enhanced electron transportation in ketopyrrole-based polymers, showing a decreased threshold voltage and inverting voltage in the transistor and inverter devices, respectively. The IID-based BBT polymers exhibit the inversion of the dominant polarity depending on the type of unsaturated carbon bridge. Owing to their strong electron-accepting ability and their highly π-extended and planar structures, <B>VBBT</B> and <B>ABBT</B> monomers should be extended to the rational design of high-performance polymers in the field of organic electronics.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2014/cmatex.2014.26.issue-17/cm500800u/production/images/medium/cm-2014-00800u_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm500800u'>ACS Electronic Supporting Info</A></P>