Origin of High Open-Circuit Voltage in Solid State Dye Solar Cells with Polymer Electrolyte

Tea-Yon Kim,Donghoon Song,Young Rae Kim,Eva M. Barea,Juan Bisquert,Yong Soo Kang 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Imidazolium Iodide-Doped PEDOT Nanofibers as Conductive Catalysts for Highly Efficient Solid-State Dye-Sensitized Solar Cells Employing Polymer Electrolyte

Kim, Tea-Yon,Wei, Wei,Lee, Tae Kyung,Kim, Byung Su,Park, Seul Chan,Lee, Sungjin,Suh, Eui Hyun,Jang, Jaeyoung,Bisquert, Juan,Kang, Yong Soo American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.3

<P>The electrical conductivity and catalytic activity of nanofibrous poly(3,4-ethylenedioxythiophene)s (PEDOT NFs) was improved by redoping with dimethyl imidazolium iodide (DMII) as a charge transfer facilitator. Addition of the new DMII dopant into the PEDOT NFs reduced the concentration of dodecyl sulfate anions (DS-) predoped during the polymerization process and concomitantly enhanced the doping concentration of I- by ion exchange. Redoping with DMII increased the mobility of the PEDOT NFs by up to 18-fold and improved the conductivity due to the enhanced linearization, suppressed aggregation, and improved crystallinity of the PEDOT chains. The catalytic activity was also improved, primarily due to the increase in the compatibility and the effective surface area upon replacement of sticky DS- with the more basic and smaller I- of DMII on the surface of the PEDOT NFs. The charge-transfer resistance across the interface between the poly(ethylene oxide)-based solid polymer electrolyte and PEDOT NF counter electrode (CE) was thus reduced to a large extent, giving an energy conversion efficiency (ECE) of 8.52% for solid-state dye-sensitized solar cells (DSCs), which is even better than that achieved with Pt CE (8.25%). This is the highest ECE reported for solid-state DSCs with conductive polymer CEs under 1 sun conditions.</P>

최근 국내 유입 Vibrio cholerae균 및 1995년도 국내 집단 발생 콜레라의 역학적 양상

김호훈,신영학,강연호,유천권,박미선,김동술,유재연,전정훈,이복권,박기덕,김동진,정태화,이종구,박기동,김상순,이동모,김문식,조병륜 대한감염학회 1996 감염 Vol.28 No.6

목적 : 1992년 이후 국내에 유입, 확인되는 V. cholerae 균은 현격한 증가 추세를 보이고 있으며, 1995년도 국내 집단 발생 콜레라의 역학적 양상이 종래의 경우와 상이한 바 있어 최근의 콜레라균 유입상황과 국내 역학적 특성을 정리하여 향후의 방역 대책에 참고로 하기 위하여 본 연구를 시행하였다. 방법 : 국내 유입 V. cholerae 균은 세균학적 방법에 의해 1986-1995년 사이에 확인된 균주를 대상으로 분석하였고, 국내 집단발생 콜레라는 1995년도에 내국인 거주자에게서 진성 콜레라 환자로 구명된 환자를 대상으로 역학적 양상을 살펴보았다. 결과 : 국내 유입 V. cholerae균은 1992년 이후 1995년 사이에 계절과 무관하게 뚜렷한 증가 추세를 보였다. 1995년도 콜레라 국내 집단 발생의 역학적 양상은 초발 환자가 인지되면서 단기간 사이에 지역적 연고가 없는 다양한 지역에서 콜레라 환자 발생이 확인되었다. 환자 발생 지역 내에서는 비교적 소규모 환자 발생에 그쳤고 진성 콜레라 환자로 확인된 환자 중 사망자는 없었으며 남성에서 여성보다 발병율이 높았다. 결론 : V.cholerae O1균의 국내 유입이 최근 현격히 증가되었고, 1994년에는 V. cholerae O139균의 국내유입이 처음으로 확인되었다. 콜레라 환자의 국내 집단 발생 위험은 1992년 이후 증가되었으며 1995년도의 집단 환자 발생은 지역적 연고가 없는 다양한 지역에서 비교적 단기간에 사망자 없이 소규모의 환자 발생양상을 보였다. Background: Imported Vibrio cholerae strains have increasingly been found since 1992 and the pattern of recent cholera epidemic outbreak in Korea showed a little difference from that of former epidemic outbreak. Methods: We had collected suspected V. cholerae isolates from Quarantine Stations or Public Health Laboratories, which were identified as V. cholerae O1 or O139. Epide miological analysis was made on the base of field surveys. Results: During the period from 1986 through 1995, 138 V. cholerae strains were imported. Nearly 85.5% of the strains (118 strains) were imported within recent 4 years from 1992 to 1995. One hundred and twenty-eight strains were E1 Tor-Ogawa type V. cholerae O1, 6 strains were V. cholerae O139 and 4 strains were E1 Tor-Inaba type V. cholerae O1. Of 138 strains, 71 strains were isolated from the airplane toilet swab and 67 strains from the passengers who entered into Korea after international travel. From 1993 to 1995, 101 strains were imported from the Southeast Asian countries; including Thailand(65), Indonesia(17), Philippines(10), Hongkong(6) Singapore(2) and Vietnam(1). During the cholera epidemic in 1995, 68 patients with V. cholerae O1 (E1 Tor-Ogawa) were found. Oneset of the index-case occurred on August 26th and the last on September 13th. Geographically it occurred in Incheon city(25), Chungcheongnam do(25), Kangwon do(6), Kyungsangbuck do(5), Kyunggi do(4), Daejeon city(2) and Pusan city(1). Of total 68 cases, 39 were male. Cases were found in all age groups, but it was more common in elderly groups. During the epidemic, E1 Tor-Ogawa type V. cholerae O1 strains were also isolated from the coastal sea water of Kanghwa kun where the epidemic outbreak occurred. Conclusions: In Korea, the imported V. cholerae O1 and V. cholerae O139 strains have increasingly been found without seasonal variation since 1992. Cholera epidemic outbreak in 1995, occurred simultaneously at many different local areas within a short period without mortality.

Origin of high open-circuit voltage in solid state dye-sensitized solar cells employing polymer electrolyte

Kim, Tea-Yon,Song, Donghoon,Barea, Eva M.,Lee, Jung Hyun,Kim, Young Rae,Cho, Woohyung,Lee, Sungjin,Rahman, Mohammed M.,Bisquert, Juan,Kang, Yong Soo unknown 2016 Nano energy Vol.28 No.-

<P><B>Abstract</B></P> <P>Herein, the energy level alignment and electron recombination kinetics in solid state dye-sensitized solar cells (DSCs) employing a solid polymer electrolyte (SPE) have been quantitatively characterized. In order to determine the microscopic origin of the enhanced characteristics in polymer electrolytes, we carried out an extensive study of the photovoltaic properties with respect to the electrolyte type and composition, including a liquid electrolyte (LE) and various salt types and concentrations. We observed a smaller downward shift in the conduction band energy of the TiO<SUB>2</SUB> layer upon contact with the SPE as well as a retarded electron recombination rate. These led to an increase in the <I>V</I> <SUB>oc</SUB> for DSCs with an SPE, which is mostly attributable to the coordinative interactions of the ethylene oxide (EO) units in poly(ethylene oxide) (PEO) and poly(ethylene glycol) dimethyl ether (PEGDME) with metallic Li<SUP>+</SUP> ions and Ti atoms. Such coordinative interactions induce 1) the capture of Li<SUP>+</SUP> cations in the bulk of the polymer electrolyte, thereby reducing their effective concentration and 2) the facile formation of a PEO passivation layer on top of the TiO<SUB>2</SUB> layer. Therefore, it was concluded that the high <I>V</I> <SUB>oc</SUB> in solid state DSCs employing a polymer electrolyte is attributable to the coordinative properties of the EO units in PEO and PEGDME in the SPE.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The origin of high open-circuit voltage in solid state dye-sensitized solar cells with PEO-based polymer electrolyte has been firstly unveiled. </LI> <LI> New quantitative analysis of TiO<SUB>2</SUB> conduction band shift was introduced by measuring the change in the Fermi voltage with varying the concentration of the salts. </LI> <LI> PEO containing the EO groups captured cations in electrolyte and also coordinatively adsorbed on the surface of the TiO<SUB>2</SUB> layer. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Surface Modification of TiO₂ Photoanodes with Fluorinated Self-Assembled Monolayers for Highly Efficient Dye-Sensitized Solar Cells

Wooh, Sanghyuk,Kim, Tea-Yon,Song, Donghoon,Lee, Yong-Gun,Lee, Tae Kyung,Bergmann, Victor W.,Weber, Stefan A. L.,Bisquert, Juan,Kang, Yong Soo,Char, Kookheon American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.46

<P>Dye aggregation and electron recombination in TiO<SUB>2</SUB> photoanodes are the two major phenomena lowering the energy conversion efficiency of dye-sensitized solar cells (DSCs). Herein, we introduce a novel surface modification strategy of TiO<SUB>2</SUB> photoanodes by the fluorinated self-assembled monolayer (F-SAM) formation with 1<I>H</I>,1<I>H</I>,2<I>H</I>,2<I>H</I>-perfluorooctyltriethoxysilane (PFTS), blocking the vacant sites of the TiO<SUB>2</SUB> surface after dye adsorption. The F-SAM helps to efficiently lower the surface tension, resulting in efficient repelling ions, e.g., I<SUB>3</SUB><SUP>–</SUP>, in the electrolyte to decrease the electron recombination rate, and the role of F-SAM is characterized in detail by impedance spectroscopy using a diffusion–recombination model. In addition, the dye aggregates on the TiO<SUB>2</SUB> surface are relaxed by the F-SAM with large conformational perturbation (i.e., helix structure) seemingly because of steric hindrance developed during the SAM formation. Such multifunctional effects suppress the electron recombination as well as the intermolecular interactions of dye aggregates without the loss of adsorbed dyes, enhancing both the photocurrent density (11.9 → 13.5 mA cm<SUP>–2</SUP>) and open-circuit voltage (0.67 → 0.72 V). Moreover, the combined surface modification with the F-SAM and the classical coadsorbent further improves the photovoltaic performance in DSCs.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-46/acsami.5b07211/production/images/medium/am-2015-072114_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b07211'>ACS Electronic Supporting Info</A></P>

Charge Transport and Light Absorption Properties of Thermally Induced Crystallization of Perovskite Solar Cells

Byung Su Kim,Tea-Yon Kim,Tae Kyung Lee,Yong Soo Kang 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Exploring Interfacial Events in Gold-Nanocluster-Sensitized Solar Cells: Insights into the Effects of the Cluster Size and Electrolyte on Solar Cell Performance

Abbas, Muhammad A.,Kim, Tea-Yon,Lee, Sang Uck,Kang, Yong Soo,Bang, Jin Ho American Chemical Society 2016 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.138 No.1

<P>Gold nanodusters (Au NCs) with molecule-like behavior have emerged as a new light harvester in various energy conversion systems. Despite several important strides made recently, efforts toward the utilization of NCs as a light harvester have been primarily restricted to proving their potency and feasibility. In solar cell applications, ground-breaking research with a power conversion efficiency (PCE) of more than 2% has recently been reported. Because of the lack of complete characterization of metal cluster-sensitized solar cells (MCSSCs), however, comprehensive understanding of the interfacial events and limiting factors which dictate their performance remains elusive. In this regard, we provide deep insight into MCSSCs for the first time by performing in-depth electrochemical impedance spectroscopy (EIS) analysis combined with physical characterization and density functional theory (DFT) calculations of Au NCs. In particular, we focused on the effect of the size of the Au NCs and electrolytes on the performance of MCSSCs and reveal that they are significantly influential on important solar cell characteristics such as the light absorption capability, charge injection kinetics, interfacial charge recombination, and charge transport. Besides offering comprehensive insights, this work represents an important stepping stone toward the development of MCSSCs by accomplishing a new PCE record of 3.8%.</P>

Triumphing over Charge Transfer Limitation of PEDOT Nanofiber with Polysulfide Mediator by 1,2-Ethanedithiol Doping at Redox Reduction Catalyst for Quantum Dot Solar Cells and H₂ Evolution

Tae Kyung LEE,Tea-Yon KIM,Byung Su KIM,Yong Soo KANG 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Electron-Transfer Kinetics through Interfaces between Electron-Transport and Ion-Transport Layers in Solid-State Dye-Sensitized Solar Cells Utilizing Solid Polymer Electrolyte

Cho, Woohyung,Lim, Jongchul,Kim, Tea-Yon,Kim, Young Rae,Song, Donghoon,Park, Taiho,Fabregat-Santiago, Francisco,Bisquert, Juan,Kang, Yong Soo American Chemical Society 2016 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.120 No.5

<P>The origin of the differences between the performance parameters found for dye-sensitized solar cells (DSCs) using liquid and poly(ethylene oxide)-based solid polymer electrolytes has been investigated. Limitations associated with poor polymer electrolyte penetration and ionic diffusion have been analyzed together with other effects such as the dye regeneration rate, the conduction band edge shift, and the electron recombination kinetics occurring in the solid polymer electrolyte. We have found that dye regeneration was faster for sensitized TiO2 films fully wetted with polymer electrolyte than that with liquid cells. This new result was attributed to a 0.2 eV decrease in the dye highest occupied molecular orbital energy yielding to an increase in the driving force for dye regeneration. These understandings may contribute to a further increase in the energy-conversion efficiency of DSCs employing solid polymer electrolyte.</P>

Anchor‐Functionalized Push‐Pull‐Substituted Bis(tridentate) Ruthenium(II) Polypyridine Chromophores: Photostability and Evaluation as Photosensitizers

Breivogel, Aaron,Wooh, Sanghyuk,Dietrich, Jan,Kim, Tea Yon,Kang, Yong Soo,Char, Kookheon,Heinze, Katja Wiley-VCH 2014 European journal of inorganic chemistry Vol. No.

<P><B>Abstract</B></P><P>Stable push‐pull substituted heteroleptic bis(tridentate) ruthenium(II) polypyridine complexes with COOH or 2,2′‐bipyridine anchor groups have been prepared and characterized by <SUP>1</SUP>H, <SUP>13</SUP>C and <SUP>15</SUP>N NMR 1D and 2D spectroscopy, infrared spectroscopy, elemental analysis, high‐resolution ESI mass spectrometry, electrochemistry, UV/Vis absorption spectroscopy, luminescence spectroscopy, and density functional calculations. The complexes feature a pronounced electronic directionality and high absorption wavelengths up to <I>λ</I><SUB>max</SUB> = 544 nm extending to 720 nm as a result of favorable push‐pull substitutions. A remarkable photostability in the presence of water and coordinating ions (I<SUP>–</SUP>) was discovered for the tridentate complexes when compared with the standard ruthenium sensitizer N719 and tris(bidentate) [Ru(bpy)<SUB>3</SUB>](PF<SUB>6</SUB>)<SUB>2</SUB>, which are highly photolabile under the same conditions (photodissociation/photosubstitution). The complexes were studied as photosensitizers in dye‐sensitized solar cells. The incident photon‐to‐current conversion efficiency follows the absorption spectra into the NIR region. However, the high positive charge of the complexes (2+) favors the recombination of the injected electrons with I<SUB>3</SUB><SUP>–</SUP> of the redox electrolyte, which is evidenced by high dark currents and short electron recombination lifetimes, leading to low cell performances compared with cells with the negatively charged N719 dye.</P>