19 research outputs found
Re-evaluation of recombination losses in dye-sensitized cells: The failure of dynamic relaxation methods to correctly predict diffusion length in nanoporous photoelectrodes
No full textPhotocurrents generated by thick, strongly absorbing, dye-sensitized cells were reduced when the electrolyte Iodine concentration was increased. Electron diffusion lengths measured using common transient techniques (L n) were at least two times higher than diffusion lengths measured at steady state (L IPCE). Charge collection efficiency calculated using Ln seriously overpredicted photocurrent, while L IPCE correctly predicted photocurrent. This has implications for optimizing cell design. © 2009 American Chemical Society.Ahn KS, 2007, J APPL PHYS, V101, DOI 10.1063-1.2721976; Barnes PRF, 2009, J PHYS CHEM C, V113, P1126, DOI 10.1021-jp809046j; Barnes PRF, 2009, J PHYS CHEM C, V113, P12615, DOI 10.1021-jp904497c; Bisquert J, 2004, J PHYS CHEM B, V108, P2313, DOI 10.1021-jp035395y; Bisquert J, 2004, J PHYS CHEM B, V108, P2323, DOI 10.1021-jp035397i; Cao YM, 2009, J PHYS CHEM C, V113, P6290, DOI 10.1021-jp9006872; Chiba Y, 2006, JPN J APPL PHYS 2, V45, pL638, DOI 10.1143-JJAP.45.L638; de Jongh PE, 1996, PHYS REV LETT, V77, P3427, DOI 10.1103-PhysRevLett.77.3427; Dor S, 2009, J PHYS CHEM C, V113, P2022, DOI 10.1021-jp808175d; Dunn HK, 2009, J PHYS CHEM C, V113, P4726, DOI 10.1021-jp810884q; Fukai Y, 2007, ELECTROCHEM COMMUN, V9, P1439, DOI 10.1016-j.elecom.2007.01.054; Gao F, 2008, J AM CHEM SOC, V130, P10720, DOI 10.1021-ja801942j; Guo L, 2007, ACTA PHYS SIN-CH ED, V56, P4270; Halme J, 2008, J PHYS CHEM C, V112, P20491, DOI 10.1021-jp806512k; Halme J, 2008, J PHYS CHEM C, V112, P5623, DOI 10.1021-jp711245f; Hamann TW, 2008, J PHYS CHEM C, V112, P10303, DOI 10.1021-jp802216p; Heimer TA, 2000, J PHYS CHEM A, V104, P4256, DOI 10.1021-jp993438y; Huang SY, 1997, J PHYS CHEM B, V101, P2576, DOI 10.1021-jp962377q; Ito S, 2008, THIN SOLID FILMS, V516, P4613, DOI 10.1016-j.tsf.2007.05.090; Jennings JR, 2008, J AM CHEM SOC, V130, P13364, DOI 10.1021-ja804852z; Jennings JR, 2007, J PHYS CHEM C, V111, P16100, DOI 10.1021-jp076457d; Kang MS, 2008, J PHOTOCH PHOTOBIO A, V195, P198, DOI 10.1016-j.jphotochem.2007.10.003; Koops SE, 2009, J AM CHEM SOC, V131, P4808, DOI 10.1021-ja8091278; Kopidakis N, 2003, J PHYS CHEM B, V107, P11307, DOI 10.1021-jp0304475; Kopidakis N., 2006, PHYS REV B, V73, P7; Liu Y, 1998, SOL ENERG MAT SOL C, V55, P267, DOI 10.1016-S0927-0248(98)00111-1; Lobato K, 2006, J PHYS CHEM B, V110, P16201, DOI 10.1021-jp063919z; Madhwani S, 2007, ENERG SOURCE PART A, V29, P721, DOI 10.1080-00908310500280926; Nazeeruddin MK, 2004, LANGMUIR, V20, P6514, DOI 10.1021-la0496082; NAZEERUDDIN MK, 1993, J AM CHEM SOC, V115, P6382, DOI 10.1021-ja00067a063; Nelson I. V., 1964, J ELECTROANAL CHEM, V7, P218, DOI 10.1016-0022-0728(64)80015-2; OREGAN B, 1990, J PHYS CHEM-US, V94, P8720, DOI 10.1021-j100387a017; O'Regan BC, 2008, J AM CHEM SOC, V130, P2906, DOI 10.1021-ja078045o; O'Regan BC, 2006, J PHYS CHEM B, V110, P17155, DOI 10.1021-jp062761f; O'Regan BC, 2009, J AM CHEM SOC, V131, P3541, DOI 10.1021-ja806869x; O'Regan BC, 2007, J PHYS CHEM C, V111, P14001, DOI 10.1021-jp073056p; OREGAN O, ACC CHEM RES UNPUB; Peter LM, 2007, J PHYS CHEM C, V111, P6601, DOI 10.1021-jp069058b; Rao C. N. R., 1972, APPL SPECTROSC, V5, P1, DOI 10.1080-05704927208081699; Schlichthorl G, 1997, J PHYS CHEM B, V101, P8141, DOI 10.1021-jp9714126; Snaith HJ, 2008, NANOTECHNOLOGY, V19, DOI 10.1088-0957-4484-19-42-424003; SODERGREN S, 1994, J PHYS CHEM-US, V98, P5552; Splan KE, 2004, J PHYS CHEM B, V108, P4111, DOI 10.1021-jp037230v; Wang M, 2009, CHEMPHYSCHEM, V10, P290, DOI 10.1002-cphc.200800708; Xia JB, 2007, J PHOTOCH PHOTOBIO A, V188, P120, DOI 10.1016-j.jphotochem.2006.11.02866686
Water-based electrolytes for dye-sensitized solar cells
No full textStable and efficient dye-sensitized solar cells based on water-containing electrolytes are shown. For water contents up to 40percent, no decrease in efficiency is seen. The cells are demonstrated to be stable for long periods of continuous illumination.This work lays a foundation for the further development of water-based cells for commercial production. © 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim.ANDERSON MA, 1988, J MEMBRANE SCI, V39, P243, DOI 10.1016-S0376-7388(00)80932-1; 'Regan B. O., 1991, NATURE, V353, P737, DOI [DOI 10.1038-353737A0, 10.1038-353737a0]; Ardo S, 2009, CHEM SOC REV, V38, P115, DOI 10.1039-b804321n; Barnes PRF, 2009, NANO LETT, V9, P3532, DOI 10.1021-nl901753k; Barnes PRF, 2009, J PHYS CHEM C, V113, P1126, DOI 10.1021-jp809046j; Green MA, 2009, PROG PHOTOVOLTAICS, V17, P320, DOI 10.1002-pip.911; Hagfeldt A, 2000, ACCOUNTS CHEM RES, V33, P269, DOI 10.1021-ar980112j; Jung YS, 2009, ELECTROCHIM ACTA, V54, P6286, DOI 10.1016-j.electacta.2009.06.006; JURIS A, 1988, COORDIN CHEM REV, V84, P85, DOI 10.1016-0010-8545(88)80032-8; Kaneko M, 2003, MACROMOL RAPID COMM, V24, P444, DOI 10.1002-marc.200390059; Koops SE, 2009, J AM CHEM SOC, V131, P4808, DOI 10.1021-ja8091278; LISKA P, 1988, J AM CHEM SOC, V110, P3686, DOI 10.1021-ja00219a068; Liu Y, 1998, SOL ENERG MAT SOL C, V55, P267, DOI 10.1016-S0927-0248(98)00111-1; Macht B, 2002, SOL ENERG MAT SOL C, V73, P163, DOI 10.1016-S0927-0248(01)00121-0; Matar F, 2008, J MATER CHEM, V18, P4246, DOI 10.1039-b808255c; Mikoshiba S, 2005, CURR APPL PHYS, V5, P152, DOI 10.1016-j.cap.2004.06.023; NAZEERUDDIN MK, 1990, HELV CHIM ACTA, V73, P1788, DOI 10.1002-hlca.19900730624; OREGAN BC, 1990, THESIS U WISCONSIN; O'Regan BC, 2004, J PHYS CHEM B, V108, P4342, DOI 10.1021-jp035613n; O'Regan BC, 2009, J AM CHEM SOC, V131, P3541, DOI 10.1021-ja806869x; O'Regan BC, 2007, J PHYS CHEM C, V111, P14001, DOI 10.1021-jp073056p; Saito H, 2004, ELECTROCHEMISTRY, V72, P310; Tropsha YG, 1997, J PHYS CHEM B, V101, P2259, DOI 10.1021-jp9629856; VLACHOPOULOS N, 1988, J AM CHEM SOC, V110, P1216, DOI 10.1021-ja00212a033; Wang P, 2005, APPL PHYS LETT, V86, DOI 10.1063-1.188782554515
A 44 kyr paleoroughness record of the Antarctic surface
No full textTwo 788 m conductivity records from ice cores drilled at Dome C, Antarctica, provide an unprecedented opportunity to examine the past roughness of the Antarctic surface. By measuring the distribution of depth differences between synchronous events in the cores, the surface height distribution can be estimated during time intervals in the past. For the first time we publish a record of this type and consider its paleoclimatic implications. The paleoroughness, originating from sastrugi and dunes on the ice sheet surface, is hypothesized to be related to the wind speed, temperature, and accumulation rate during the period of preservation. The roughness record indicates only a slight decrease in the preserved surface roughness from the last glacial period (0.031 m root mean square (r.m.s.) of surface deviation) to the present (0.029 m r.m.s.). This result is surprising given the large change in temperature and accumulation rate that occurred during the last climatic transition. However, it could be consistent with modeling results suggesting low wind speeds on the East Antarctic Plateau during the last ice age if the possible influences of the accumulation and temperature changes are ignored. Additionally, the reliability of the Dome C ice core record is assessed, and the probability of short-term events being missing from the profile is determined. These results are of particular interest when constraining the proportion of events that may be synchronously matched with other ice cores. The principles and results present here allow inferences about the natural variation in ice core records generally
What makes dye cells tick, or kick the bucket? Injection, regeneration, and collection efficiencies in new, old, dry, and wet dye sensitized solar cells
No full textDSC electrolytes tolerant of water are demonstrate (figure 1). Some with surprising stability (figure 2). TAS data of complete cells allows determination of the rate constants for regeneration of S+ and electron recombination with S+ (figure 3). Luminescence lifetime (figure 4) of a large variety of cells, light soaked or thermally treated, indicate that the photocurrent can be explained by slow injection. We address diffusion length, its definition, determination, and relation to the empirical optimum thickness for DSCs
What makes dye cells tick, or kick the bucket? Injection, regeneration, and collection efficiencies in new, old, dry, and wet dye sensitized solar cells
No full textDSC electrolytes tolerant of water are demonstrate (figure 1). Some with surprising stability (figure 2). TAS data of complete cells allows determination of the rate constants for regeneration of S+ and electron recombination with S+ (figure 3). Luminescence lifetime (figure 4) of a large variety of cells, light soaked or thermally treated, indicate that the photocurrent can be explained by slow injection. We address diffusion length, its definition, determination, and relation to the empirical optimum thickness for DSCs
A technique for the examination of polar ice using the scanning electron microscope
No full textThe microstructure and location of impurities in polar ice are of great relevance to ice core studies. We describe a reliable method to examine ice in the scanning electron microscope (SEM). Specimens were cut in a cold room and could have their surfaces altered by sublimation either before (pre-etching) or after (etching) introduction to the cryo-chamber of the SEM. Pre-etching was used to smooth surfaces, whilst etching stripped away layers from the specimen surface, aiding the location of particles in situ, and allowing embedded structures to be revealed. X-ray analysis was used to determine the composition of localized impurities, which in some cases had been concentrated on the surface by etching. Examining uncoated surfaces was found to be advantageous and did not detract from qualitative X-ray analysis. Imaging uncoated was performed at low accelerating voltages and probe currents to avoid problems of surface charging
Do counter electrodes on metal substrateswork with cobalt complex based electrolyte in dye sensitized solar cells?
No full textYes. Testing 7 different metals as a substrate for a counter electrode in dye sensitized solar cells (DSSC) showed that some metals can be a good option for use with cobalt electrolyte. It was found that Stainless steels 304 and 321 as well as Ni and Ti suit well to the counter electrodes in DSSCs with cobalt electrolyte. In these 4 cases both the efficiency and the lifetime were similar to the reference cells on conducting glass substrates. In contrast, the cells with Al, Cu and Zn substrates suffered from both a low efficiency and a poor stability. These three metals had clear marks of corrosion such as apparent corrosion products in the aged cells. Additionally, we also investigated how the different types of catalyst materials perform in the case of a metal counter electrode (stainless steel 304) with cobalt electrolyte in comparison to reference glass cells. Among the 5 different catalyst layers the best results for stainless steel electrode were achieved with low temperature platinization whereas polymer catalysts poly(3,4-ethylenedioxythiophene)-ptoluenesulfone and poly(3,4-ethylenedioxythiophene)-polystyrenesulfone that worked well on the glass worked very poorly on the metal. © 2012 The Electrochemical Society.Chen CM, 2010, ELECTROCHIM ACTA, V55, P1687, DOI 10.1016-j.electacta.2009.10.050; Fang X., 2005, THIN SOLID FILMS, V427, P242; Feldt SM, 2010, J AM CHEM SOC, V132, P16714, DOI 10.1021-ja1088869; Hashmi G, 2011, RENEW SUST ENERG REV, V15, P3717, DOI 10.1016-j.rser.2011.06.004; Ito S, 2005, CHEM COMMUN, P4351, DOI 10.1039-b505718c; Jennings JR, 2011, PHYS CHEM CHEM PHYS, V13, P6637, DOI 10.1039-c0cp02605k; Kalowekamo J, 2009, SOL ENERGY, V83, P1224, DOI 10.1016-j.solener.2009.02.003; Kroon JM, 2007, PROG PHOTOVOLTAICS, V15, P1, DOI 10.1002-pip.707; Law CH, 2010, ADV MATER, V22, P4505, DOI 10.1002-adma.201001703; Li DM, 2010, ADV FUNCT MATER, V20, P3358, DOI 10.1002-adfm.201000150; Liberatore M, 2009, APPL PHYS LETT, V94; Liu JY, 2011, ENERG ENVIRON SCI, V4, P3021, DOI 10.1039-c1ee01633d; Ma TL, 2004, J ELECTROANAL CHEM, V574, P77, DOI 10.1016-j.jelechem.2004.08.002; Miettunen K, 2011, J ELECTROANAL CHEM, V653, P93, DOI 10.1016-j.jelechem.2010.12.022; Miettunen K, 2010, J ELECTROCHEM SOC, V157, pB814, DOI 10.1149-1.3374645; Miettunen K, 2007, P 22 EUR PHOT SOL EN, P512; Miettunen K, 2010, CARBON, V49, P528; Reynolds GJ, 2011, ECS TRANSACTIONS, V33, P129, DOI 10.1149-1.3553355; Sapp SA, 2002, J AM CHEM SOC, V124, P11215, DOI 10.1021-ja027355y; Toivola M, 2006, SOL ENERG MAT SOL C, V90, P2881, DOI 10.1016-j.solmat.2006.05.002; Tsao HN, 2011, ENERG ENVIRON SCI, V4, P4921, DOI 10.1039-c1ee02389f; XU WW, 1990, MATER RES BULL, V25, P1385, DOI 10.1016-0025-5408(90)90221-M; Yella A, 2011, SCIENCE, V334, P629, DOI 10.1126-science.120968879
The reorganization energy of intermolecular hole hopping between dyes anchored to surfaces
No full textEvolution of chemical peak shapes in the Dome C, Antarctica, ice core
No full text[1] Interpretation of the chemical layers measured in ice cores requires knowledge of processes occurring after their deposition on the ice sheet. We present evidence for the diffusion of soluble ions in the top 350 m of the Dome C ice core, Antarctica, that helps in explaining the unexpectedly broad volcanic peaks observed at depth. A windowed-differencing operation applied to chemical time series indicates a damping of the signals over the past 11,000 years, independent of minor climatic variation, for sulfate and chloride, but not sodium. This implies a diffusive process is transporting both sulfate and chloride ions while the sodium ions remain fixed. We estimate the effective diffusivity in the core to be 4.7 x 10(-8) m(2) yr(-1) for sulfate and 2.0 x 10(-7) m(2) yr(-1) for chloride. These values are not high enough to significantly disrupt chemical interpretation in this section of core, but could be significant for older ice. The temperature of this section of ice (-53degreesC) implies that the predominantly acidic sulfate (and possibly chloride ions) will exist in the liquid phase while the sodium may be solid. We propose and develop two new mechanisms that could explain the observed solute movement. One involves the diffusion of solute through a connected vein network driven by liquid concentration imbalances instigated by the process of grain growth. The other considers a system of discontinuous veins where grain growth increases connectivity between isolated vein clusters allowing the spread of solute. In both mechanisms, the effective diffusivity is governed indirectly by grain growth rate; this may be a significant factor controlling effective diffusion in other cores
Effect of density on electrical conductivity of chemically laden polar ice
No full text[1] Electrical conductivity measurements made using the dielectric profiling technique (DEP) are compared to chemical data from the top 350 m of the Dome C ice core in Antarctica. The chemical data are used to calculate the concentration of the major acidic impurities in the core: sulphuric acid and hydrochloric acid. The conductivity coefficients in solid ice for sulphuric acid (beta(H2SO4)) and hydrochloric acid (beta(HCl)) are found to be 4.9 and 4.5 S m(-1) M-1. These are consistent with previously found values for the acid conductivity coefficient at different sites and suggest that the same conductivity mechanisms are important in all polar ice. A method of rolling regression analysis is used to find the variation of the pure ice conductivity (sigma(infinity) pure) and the conductivity coefficient of sulphuric acid, beta(H2SO4), with depth. Then sigma(infinity) pure and beta(H2SO4) are assessed against changes in core density and hence volume fraction of ice, nu, due to the inclusion of air bubbles in the firn. Looyenga's model for dielectric mixtures applied to conduction in firn broadly predicts the variation observed in sigma(infinity) pure but does not fit well for ice above 110 m. A previous application of the theory of percolation in random lattices is used to model the conductivity coefficient in firn. The coefficient beta(H2SO4) is linked to nu by the power law: beta(H2SO4)(nu) proportional to beta(H2SO4) (1) (nu - nu(c))(t); where nu(c) is a threshold volume fraction below which no conduction can take place and is related to the geometry of the conducting lattice being modeled. The value of the exponent t is also dependent on the structure of the lattice and is here found to be t = 2.5, which is slightly lower than the previously obtained value of t = 2.7 for a structure where each grain has between 14 and 16 nearest neighbors. This model is consistent with the concept of conduction, via liquid H2SO4, taking place at two grain boundaries for firn. The model does not, however, preclude conduction taking place via acid situated at three grain boundaries or in an interconnected vein network at densities above 640 kg m(-3)
