Importance of 4-<i>tert</i>-Butylpyridine in Electrolyte for Dye-Sensitized Solar Cells Employing SnO₂ Electrode

Kim, Jae-Yup,Kim, Jin Young,Lee, Doh-Kwon,Kim, BongSoo,Kim, Honggon,Ko, Min Jae American Chemical Society 2012 The Journal of Physical Chemistry Part C Vol.116 No.43

<P>The photovoltaic performance of dye-sensitized solar cells (DSSCs) employing SnO<SUB>2</SUB> electrodes was investigated while increasing the content of 4-<I>tert</I>-butylpyridine (TBP) in the conventional liquid-type electrolyte. As the added TBP content increased, the open circuit voltage (<I>V</I><SUB>oc</SUB>) and conversion efficiency were highly enhanced while the short circuit current (<I>J</I><SUB>sc</SUB>) was not much affected. With the electrolyte of 2.0 M TBP, the <I>V</I><SUB>oc</SUB> and conversion efficiency were increased by 26 and 33%, respectively, compared with the conventional electrolyte (0.5 M TBP). The electrochemical impedance spectra revealed that the enhancement of <I>V</I><SUB>oc</SUB> resulted from the negative shift of the SnO<SUB>2</SUB> conduction band potential and the increase in resistance of electron recombination by 1 order of magnitude. It is noteworthy that the optimized concentration of TBP for the SnO<SUB>2</SUB> electrode is greatly larger than that for the TiO<SUB>2</SUB> electrode. This may be due to the much faster electron recombination rate and more positive conduction band potential of the SnO<SUB>2</SUB> electrode. The SnO<SUB>2</SUB> electrode modified with TiO<SUB>2</SUB> shell showed only slightly enhanced performance due to the similar effects of shell layer and those of the TBP. In contrast to the SnO<SUB>2</SUB>, TiO<SUB>2</SUB> electrodes did not show performance enhancement with the electrolyte of TBP concentration larger than 0.5 M. The impedance spectra of symmetric dummy cells employing Pt counter electrodes indicated that the catalytic effect of Pt was deteriorated, and the resistance of electrolyte diffusion was increased by the higher concentration of TBP. This brings up the need for development of a counter electrode that TBP is not easily adsorbed on, and alternative additives to TBP which are not highly viscous.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-43/jp307783q/production/images/medium/jp-2012-07783q_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp307783q'>ACS Electronic Supporting Info</A></P>

Correlation between Crystallinity, Charge Transport, and Electrical Stability in an Ambipolar Polymer Field-Effect Transistor Based on Poly(naphthalene-<i>alt</i>-diketopyrrolopyrrole)

Kim, Beom Joon,Lee, Hyo-Sang,Lee, Joong Seok,Cho, Sanghyeok,Kim, Hyunjung,Son, Hae Jung,Kim, Honggon,Ko, Min Jae,Park, Sungnam,Kang, Moon Sung,Oh, Se Young,Kim, BongSoo,Cho, Jeong Ho American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.22

<P>We characterized the electrical properties of ambipolar polymer field-effect transistors (PFETs) based on the low-band-gap polymer, pNAPDO-DPP-EH. The polymer consisted of electron-rich 2,6-di(thienyl)naphthalene units with decyloxy chains (NAPDO) and electron-deficient diketopyrrolopyrrole units with 2-ethylhexyl chains (DPP-EH). The as-spun pNAPDO-DPP-EH PFET device exhibited ambipolar transport properties with a hole mobility of 3.64 × 10<SUP>–3</SUP> cm<SUP>2</SUP>/(V s) and an electron mobility of 0.37 × 10<SUP>–3</SUP> cm<SUP>2</SUP>/(V s). Thermal annealing of the polymer film resulted in a dramatic increase in the carrier mobility. Annealing at 200 °C yielded hole and electron mobilities of 0.078 and 0.002 cm<SUP>2</SUP>/(V s), respectively. The mechanism by which the mobility had improved was investigated via grazing incidence X-ray diffraction studies, atomic force microscopy, and temperature-dependent transport measurements. These results indicated that thermal annealing improved the polymer film crystallinity and promoted the formation of a longer-range lamellar structure that lowered the thermal activation energy for charge hopping. Thermal annealing, moreover, reduced charge trapping in the films and thus improved the electrical stability of the PFET device. This work underscores the fact that long-range ordering in a crystalline polymer is of great importance for efficient charge transport and high electrical stability.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-22/jp400664r/production/images/medium/jp-2013-00664r_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp400664r'>ACS Electronic Supporting Info</A></P>

Carrier Lifetime Extension via the Incorporation of Robust Hole/Electron Blocking Layers in Bulk Heterojunction Polymer Solar Cells

Yoon, Youngwoon,Kim, Hyeong Jun,Cho, Chul-Hee,Kim, Seulki,Son, Hae Jung,Ko, Min-Jae,Kim, Honggon,Lee, Doh-Kwon,Kim, Jin Young,Lee, Wonmok,Kim, Bumjoon J.,Kim, BongSoo American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.1

<P>We report the achievement of a power conversion efficiency (PCE) improvement in P3HT:PCBM-based bulk-heterojunction type polymer solar cells using photocrosslinked P3HT (c-P3HT) as the electron blocking/hole extraction layer and titanium oxide nanoparticles (TiO<SUB>2</SUB>) as the hole blocking/electron extraction layer. Devices prepared with a 20 nm thick c-P3HT layer showed an improved PCE of 3.4% compared to devices prepared without the c-P3HT layer (PCE = 3.0%). This improvement was attributed to an extension in the carrier lifetime and an enhancement in the carrier mobility. The incorporation of the c-P3HT layer lengthened (by more than a factor of 2) the carrier lifetime and increased (by a factor of 5) the hole mobility. These results suggest that the c-P3HT layer not only prevented non-geminate recombination but it also improved carrier transport. The PCE was further improved to 4.0% through the insertion of a TiO<SUB>2</SUB> layer that acted as an effective hole-blocking layer at the interface between the photoactive layer and the cathode. This work demonstrates that the incorporation of solution-processable hole and electron blocking/extraction layers offers an effective means for preventing nongeminate recombination at the interfaces between a photoactive layer and an electrode in bulk-heterojunction-type 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-1/am404381e/production/images/medium/am-2013-04381e_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am404381e'>ACS Electronic Supporting Info</A></P>

Correlation between Polymer Structure and Polymer:Fullerene Blend Morphology and Its Implications for High Performance Polymer Solar Cells

Son, Seon Kyoung,Kim, Youn-Su,Son, Hae Jung,Ko, Min Jae,Kim, Honggon,Lee, Doh-Kwon,Kim, Jin Young,Choi, Dong Hoon,Kim, Kyungkon,Kim, BongSoo American Chemical Society 2014 The Journal of Physical Chemistry Part C Vol.118 No.5

<P>We synthesized four polymers (pT3DPP-HD, pT3DPP-OD, pT2TTDPP-HD, and pT2TTDPP-OD) and characterized their photovoltaic properties as a function of the backbone planarity, alkyl side chain length, and film morphology. The polymers were donor–acceptor type low-band-gap (1.2–1.3 eV) polymers employing terthiophene (T3) or thiophene–thieno[3,2-<I>b</I>]thiophene–thiophene (T2TT) as the donor and 2,5-bis(2-hexyldecyl)pyrrolo[3,4-<I>c</I>]pyrrole-1,4-(2<I>H</I>,5<I>H</I>)-dione (DPP-HD) or 2,5-bis(2-octyldodecyl)pyrrolo[3,4-<I>c</I>]pyrrole-1,4-(2<I>H</I>,5<I>H</I>)-dione (DPP-OD) as the acceptor. The T2TT moiety in the polymer backbone is more planar than the T3; the OD moiety as the alkyl side chain ensured a higher solubility than the HD moiety. Polymer solar cells (PSCs) were fabricated, and their properties were characterized. The photoactive layer consisted of one of the four polymers and one of the fullerene derivatives (PC<SUB>70</SUB>BM or PC<SUB>60</SUB>BM). For a given fullerene derivative, the PCEs prepared with each of the four polymers were ordered according to pT3DPP-OD, pT2TTDPP-HD, pT3DPP-HD, and pT2TTDPP-OD. Studies on the morphologies of the polymer:fullerene layers revealed that the pT3DPP-OD:PC<SUB>70</SUB>BM blend exhibited an optimal degree of phase separation between the polymer and the fullerene, while retaining a high degree of interconnectivity, thereby yielding the highest PCE measured in this series. By contrast, the pT2TTDPP-OD:fullerene yielded the lowest PCE because of too high crystalline fibrous polymer domains. In conclusion, we demonstrate that minute variations in the polymer chemical structure strongly affects both (i) the nanoscale miscibility between the polymers and fullerenes and (ii) the interconnectivity of the polymer chains, and these properties are tightly correlated with the solar cell performance.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2014/jpccck.2014.118.issue-5/jp405744d/production/images/medium/jp-2013-05744d_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp405744d'>ACS Electronic Supporting Info</A></P>

Water-Based Thixotropic Polymer Gel Electrolyte for Dye-Sensitized Solar Cells

Park, Se Jeong,Yoo, Kichoen,Kim, Jae-Yup,Kim, Jin Young,Lee, Doh-Kwon,Kim, BongSoo,Kim, Honggon,Kim, Jong Hak,Cho, Jinhan,Ko, Min Jae American Chemical Society 2013 ACS NANO Vol.7 No.5

<P>For the practical application of dye-sensitized solar cells (DSSCs), it is important to replace the conventional organic solvents based electrolyte with environmentally friendly and stable ones, due to the toxicity and leakage problems. Here we report a noble water-based thixotropic polymer gel electrolyte containing xanthan gum, which satisfies both the environmentally friendliness and stability against leakage and water intrusion. For application in DSSCs, it was possible to infiltrate the prepared electrolyte into the mesoporous TiO<SUB>2</SUB> electrode at the fluidic state, resulting in sufficient penetration. As a result, this electrolyte exhibited similar conversion efficiency (4.78% at 100 mW cm<SUP>–2</SUP>) and an enhanced long-term stability compared to a water-based liquid electrolyte. The effects of water on the photovoltaic properties were examined elaborately from the cyclic voltammetry curves and impedance spectra. Despite the positive shift in the conduction band potential of the TiO<SUB>2</SUB> electrode, the open-circuit voltage was enhanced by addition of water in the electrolyte due to the greater positive shift in the I<SUP>–</SUP>/I<SUB>3</SUB><SUP>–</SUP> redox potential. However, due to the dye desorption and decreased diffusion coefficient caused by the water content, the short-circuit photocurrent density was reduced. These results will provide great insight into the development of efficient and stable water-based electrolytes.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2013/ancac3.2013.7.issue-5/nn4001269/production/images/medium/nn-2013-001269_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn4001269'>ACS Electronic Supporting Info</A></P>

Cu(<small>I</small>)-containing room temperature ionic liquids as selective and reversible absorbents for propyne

Kim, Jin Hyung,Palgunadi, Jelliarko,Mukherjee, Deb Kumar,Lee, Hyun Joo,Kim, Honggon,Ahn, Byoung Sung,Cheong, Minserk,Kim, Hoon Sik Royal Society of Chemistry 2010 Physical chemistry chemical physics Vol.12 No.42

<P>A Cu(<SMALL>I</SMALL>)-containing room temperature ionic liquid (Cu-RTIL), prepared from CuCl and 1,3-dimethylimidazolium methylphosphite ([DMIM][MeHPO<SUB>3</SUB>]), was found to reversibly and selectively interact with propyne over propylene. Cu-RTIL exhibited 12 times higher propyne absorption capacity and 14 times higher ideal propyne/propylene selectivity than [DMIM][MeHPO<SUB>3</SUB>]. Fast atom bombardment (FAB)-mass spectral and computational results with Cu-RTIL (CuCl/[DMIM][MeHPO<SUB>3</SUB>] = 1/2) strongly imply that the Cu-RTIL contains stable methylphosphite-coordinated anionic Cu(<SMALL>I</SMALL>) species such as CuCl(MeHPO<SUB>3</SUB>)<SUP>−</SUP> and Cu(MeHPO<SUB>3</SUB>)<SUB>2</SUB><SUP>−</SUP>. Computational studies on the optimized structures demonstrate that the preferential absorption of propyne over propylene in a Cu-RTIL originates from the difference in the interaction mode between the coordinated phosphite ligand and propyne or propylene. Strong π-complexation of propylene and propyne with Cu in Cu-RTIL is not observed.</P> <P>Graphic Abstract</P><P>A Cu(<SMALL>I</SMALL>)-containing room temperature ionic liquid (Cu-RTIL), prepared from CuCl and 1,3-dimethylimidazolium methylphosphite ([DMIM][MeHPO<SUB>3</SUB>]), was found to reversibly and selectively interact with propyne over propylene. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c004140h'> </P>

The Fluorination of 1,1,1- trifluoro -2,2- dichloroethane to Pentafluoroethane over Cr - based Catalyst

Kim, Hoon Sik,Lee, Byung Gwon,Kim, Honggon,Lee, Sang Deuk,Seo, Inseok 한국공업화학회 1997 Journal of Industrial and Engineering Chemistry Vol.3 No.2

The fluorination reaction of 1,1,1-trifluoro-2,2,-dichloroethane (CF₃CHCl₂, HCFC-123) to pentafluoroethane (CF₃CHF₂, HFC-125) has been studied under atmospheric pressure at the temperature range of 250 - 380℃ over Cr-based catalyst. The catalyst comprised Cr, one component selected from the group consisting of Mg or Ca and at least one metal component selected from the group consisting of Ce, Zn and Ni. The effects of catalyst compositions, molar ratio of reactants (HF/HCFC-123), reaction temperature, contact time on the catalytic activities were extensively investigated. The catalytic performance of chromium oxide mixed with metallic compounds has been found to be much improved as compared with that of chromium oxide catalyst alone. Especially, the presence of metallic compounds in the chromium oxide catalyst has shown the outstanding capability of slowing down the catalyst deactivation by retarding the carbon deposition on the catalyst.

메탄으로부터 수소생산용 촉매 개발

김필(Pil Kim),김희수(Heesoo Kim),박영근(Younggeun Park),이재호(Jae Ho Lee),김홍곤(Honggon Kim),이종협(Jongheop Yi) 한국가스학회 2003 한국가스학회 학술대회논문집 Vol.2003 No.10

Simultaneous Enhancement of Solar Cell Efficiency and Photostability via Chemical Tuning of Electron Donating Units in Diketopyrrolopyrrole-Based Push–Pull Type Polymers

Ryu, Tae In,Yoon, Youngwoon,Kim, Ji-Hoon,Hwang, Do-Hoon,Ko, Min Jae,Lee, Doh-Kwon,Kim, Jin Young,Kim, Honggon,Park, Nam-Gyu,Kim, BongSoo,Son, Hae Jung American Chemical Society 2014 Macromolecules Vol.47 No.18

<P>We synthesized a series of push–pull-type copolymers by copolymerizing an electron-deficient diketopyrrolopyrrole with three electron-donating benzodithiophene (BDT) moieties. PDPPDTT, which incorporated a dithienothiophene (DTT), showed a higher power conversion efficiency (PCE) of 6.11% compared to 3.31% for the BDT-based polymer (PDPPBDT). PDPPDTBDT, which incorporated a dithienobenzodithiophene (DTBDT), also exhibited superior performance, with a PCE of 4.75% although this value was lower than that obtained for PDPPDTT. The presence of the DTT unit in the polymer backbone lowered the energy bandgap of the polymer and induced an optimal morphology in the polymer:PC<SUB>71</SUB>BM blend film, resulting in higher charge carrier generation. Furthermore, the effectively delocalized frontier orbitals of PDPPDTT enhanced intermolecular interactions between the polymer chains by favoring effective π–π stacking, which facilitated charge carrier transport. By contrast, PDPPDTBDT unexpectedly showed a low-crystallinity thin film despite its backbone planarity, which reduced the performance relative to that of PDPPDTT. Importantly, PDPPDTT exhibited significantly better device stability compared to the other polymers in a light soaking test due to the much higher photochemical stability of PDPPDTT. We demonstrated a systematic approach to simultaneously increasing the photovoltaic performances and device stability, and we explored the basis for the structure–property relationship that accompanied such improvements.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2014/mamobx.2014.47.issue-18/ma501300a/production/images/medium/ma-2014-01300a_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ma501300a'>ACS Electronic Supporting Info</A></P>

Binder-Free Cu–In Alloy Nanoparticles Precursor and Their Phase Transformation to Chalcogenides for Solar Cell Applications

Lim, Ye Seul,Jeong, Jeunghyun,Kim, Jin Young,Ko, Min Jae,Kim, Honggon,Kim, BongSoo,Jeong, Unyong,Lee, Doh-Kwon American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.23

<P>A low-cost, nonvacuum fabrication route for CuInSe<SUB>2</SUB> and CuInS<SUB>2</SUB> thin films is presented. To produce these films, binder-free colloidal precursors were prepared using Cu–In intermetallic nanoparticles that were synthesized via a chemical reduction method. The Cu–In alloy precursor films were transformed to CuInSe<SUB>2</SUB> and CuInS<SUB>2</SUB> by reactive annealing in chalcogen-containing atmospheres at atmospheric pressure. The as-synthesized nanoparticles and the annealed films were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, energy dispersive X-ray spectrometry, electron probe X-ray microanalysis, Raman spectroscopy, and Auger electron spectroscopy depth profile measurements to elucidate the phase evolution pathway and the densification mechanism of the Cu–In–Se–S system. Solar cell devices made with CuInSe<SUB>2</SUB> and CuInS<SUB>2</SUB> absorbing layers exhibited power conversion efficiencies of 3.92% and 2.28%, respectively. A comparison of the devices suggested that the microstructure of the absorbing layer had a greater influence on the overall photovoltaic performance than the band gap energy. A diode analysis on the solar cell devices revealed that the high saturation current density and diode ideality factor caused lower open-circuit voltages than would be expected from the band gap energies. However, the diode analysis combined with the microstructural and compositional analysis offered guidance about how to improve the photovoltaic performance of these devices.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-23/jp401637b/production/images/medium/jp-2013-01637b_0013.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp401637b'>ACS Electronic Supporting Info</A></P>