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  • 1.
    Aung, Su Htike
    et al.
    Uppsala Univ, Dept Chem, Angstrom Lab, POB 523, S-75120 Uppsala, Sweden.;Univ Mandalay, Dept Phys, Mat Sci Res Lab, Mahaaungmyay Township 100103, Mandalay, Myanmar..
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Oo, Than Zaw
    Univ Mandalay, Dept Phys, Mat Sci Res Lab, Mahaaungmyay Township 100103, Mandalay, Myanmar..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    2-(4-Butoxyphenyl)-N-hydroxyacetamide: An Efficient Preadsorber for Dye-Sensitized Solar Cells2017In: ACS OMEGA, ISSN 2470-1343, Vol. 2, no 5, p. 1820-1825Article in journal (Refereed)
    Abstract [en]

    The effect of chemical modification of mesoporous TiO2 electrodes by 2-(4-butoxyphenyl)-N-hydroxyacetamide (BPHA) before dye adsorption is investigated in dye-sensitized solar cells (DSCs). Two organic dyes, LEG4 and Dyenamo blue, were used in combination with the cobalt (II/III) tris(bipyridine) redox couple. The photovoltaic performance of the DSCs is clearly enhanced by BPHA. Preadsorption of mesoporous TiO2 electrodes with BPHA lowered the amount of adsorbed dye but improved the shortcircuit current densities and the power conversion efficiencies by 10-20%, while keeping the open-circuit potential essentially unaffected. Notably, BPHA improved the LEG4 performance, whereas it has been reported for this dye that chenodeoxycholic acid as a coadsorbent lowers solar cell efficiency. Faster dye regeneration was found to be one reason for improved performance, but improved electron injection efficiency may also contribute to the favorable effect of BPHA.

  • 2.
    Aung, Su Htike
    et al.
    Mandalay Univ, Mat Sci Res Lab, Dept Phys, Mandalay, Myanmar..
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Oo, Than Zaw
    Mandalay Univ, Mat Sci Res Lab, Dept Phys, Mandalay, Myanmar..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Kinetic study of carminic acid and santalin natural dyes in dye-sensitized solar cells2016In: Journal of Photochemistry and Photobiology A: Chemistry, ISSN 1010-6030, E-ISSN 1873-2666, Vol. 325, p. 1-8Article in journal (Refereed)
    Abstract [en]

    The performance of natural dyes in dye-sensitized solar cells is usually worse than that of purpose-built organic dyes. Here, we set out to investigate the underlying origins. Two natural dyes, carminic acid and santalin, were selected as potential sensitizers for dye-sensitized solar cells. They were compared to a state-of-the-art organic sensitizer, LEG4, in devices using relatively thin (5 mu m), transparent mesoporous TiO2 electrodes and iodide/triiodide redox electrolyte in the low-volatile solvent 3-methoxypropionitrile. All dyes adsorbed well onto mesoporous TiO2 electrodes, giving it bright red colors. The power conversion efficiency of the natural dyes, about 0.5%, was poor compared to that of LEG4 under identical conditions (5.6%), due to both lower open circuit potentials and photocurrent densities. The origin of low efficiencies was investigated using a wide range of experimental techniques, such as (spectro)electrochemistry, ns-laser transient absorption spectroscopy and transient photocurrent and photovoltage measurements. The kinetics for regeneration of the oxidized natural dyes by iodide was found to about ten times slower than that of LEG4. This is probably due to the lower driving force for this reaction. Significant electron recombination to oxidized dye molecules and possibly poor electron injection efficiency caused the poor performance of the two natural dyes in dye-sensitized solar cells. In addition, for carminic acid electron injection into the conduction band of TiO2 appears to be poor. (C) 2016 Published by Elsevier B.V.

  • 3. Cong, Jiayan
    et al.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Kloo, Lars
    Electrolytes Based on TEMPO-Co Tandem Redox Systems Outperform Single Redox Systems in Dye-sensitized Solar Cells2015In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 8, no 2, p. 264-268Article in journal (Refereed)
    Abstract [en]

    A new TEMPO-Co tandem redox system with TEMPO and Co(bpy)(3)(2+/3+) has been investigated for the use in dye-sensitized solar cells (DSSCs). A large open-circuit voltage (V-OC) increase, from 862 mV to 965 mV, was observed in the tandem redox system, while the short-circuit current density (J(SC)) was maintained. The conversion efficiency was observed to increase from 7.1% for cells containing the single Co(bpy)(3)(2+/3+) redox couple, to 8.4% for cells containing the TEMPO-Co tandem redox system. The reason for the increase in V-OC and overall efficiency is ascribed to the involvement of partial regeneration of the sensitizing dye molecules by TEMPO. This assumption can be verified through the observed much faster regeneration dynamics exhibited in the presence of the tandem system. Using the tandem redox system, the faster recombination problem of the single TEMPO redox couple is resolved and the mass-transport of the metal-complex-based electrolyte is also improved. This TEMPO-Co tandem system is so far the most effienct tandem redox electrolyte reported not involving iodine. The current results show a promising future for tandem system as replacements for single redox systems in electrolytes for DSSCs.

  • 4. Cong, Jiayan
    et al.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    Kloo, Lars
    Two Redox Couples are Better Than One: Improved Current and Fill Factor from Cobalt-Based Electrolytes in Dye-Sensitized Solar Cells2014In: ADV ENERGY MATER, ISSN 1614-6832, Vol. 4, no 8, p. 1301273-Article in journal (Refereed)
  • 5. Fan, Jiandong
    et al.
    Fabrega, Cristian
    Zamani, Reza R.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Parra, Andres
    Andreu, Teresa
    Arbiol, Jordi
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ramon Morante, Joan
    Cabot, Andreu
    Enhanced Photovoltaic Performance of Nanowire Dye-Sensitized Solar Cells Based on Coaxial TiO2@TiO Heterostructures with a Cobalt(II/III) Redox Electrolyte2013In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, no 20, p. 9872-9877Article in journal (Refereed)
    Abstract [en]

    The growth of a TiO shell at the surface of TiO2 nanowires (NWs) allowed us to improve the power conversion efficiency of NW-based dye-sensitized solar cells (DSCs) by a factor 2.5. TiO2@TiO core-shell NWs were obtained by a two-step process: First, rutile-phase TiO2 NWs were hydrothermally grown. Second, a hongquiite-phase TiO shell was electrochemically deposited at the surface of the TiO2 NWs. Bare TiO2 and heterojunction TiO2@TiO NW-based DSCs were obtained using a cobalt(II/III) redox electrolyte and LEG4 as the dye. With this electrolyte/dye combination, DSCs with outstanding V-oc values above 900 mV were systematically obtained. While TiO2@TiO NW-based DSCs had slightly lower V-oc values than bare TiO2 NW-based DSCs, they provided 3-fold higher photocurrents, overall reaching 2.5-fold higher power conversion efficiencies. The higher photocurrents were associated with the larger surface roughness and an enhanced charge-carrier separation/transfer at the NW/dye interface.

  • 6. Fan, Jiandong
    et al.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Cabot, Andreu
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Cobalt(II/III) Redox Electrolyte in ZnO Nanowire-Based Dye-Sensitized Solar Cells2013In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 5, no 6, p. 1902-1906Article in journal (Refereed)
    Abstract [en]

    In this work, we explore the use of cobalt complex redox shuttles in dye sensitized solar cells (DSCs) based on ZnO nanowires (NWs). Arrays of vertically aligned ZnO NWs produced by a low-cost hydrothermal method are used to fabricate DSCs with [Co(bpy)(3)](2+/3+) as electrolyte. A direct comparison of the performance of [Co(bpy)(3)](2+/3+)-based ZnO DSC with I-/I-3(-)-based ones demonstrates the higher suitability of the cobalt complex, both in terms of a larger open circuit voltage (V-OC) and a higher photocurrent. The [Co(bpy)(3)](2+/3+) electrolyte results in V-OC enhancements above 200 mV. This V-OC increase is associated to the better match between the cobalt complex redox potential and the oxidation potential of the dye. The incident photon-to-current efficiency (IPCE) enhancement is attributed to a less competitive visible light absorption of the cobalt redox couple. Thus the present study opens new opportunities to improve energy conversion efficiency in ZnO-based DSCs.

  • 7. Fan, Jiandong
    et al.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Munuera, Carmen
    Garcia-Hernandez, Mar
    Gueell, Frank
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Cabot, Andreu
    Influence of the Annealing Atmosphere on the Performance of ZnO Nanowire Dye-Sensitized Solar Cells2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 32, p. 16349-16356Article in journal (Refereed)
    Abstract [en]

    Postsynthesis thermal treatments are key to promote crystallinity and reduce the defect density in solution-processed nanomaterials. In particular, the annealing atmosphere strongly influences the functional properties of ZnO nanowires (NWs) and specifically their performance as photoanodes in dye-sensitized solar cells (DSCs). We prepared vertically aligned ZnO NWs by a low-cost, high-yield, and up-scalable hydrothermal method and studied the effect of the postannealing atmosphere on their optoelectronic properties and on their performance as electrodes in DSCs. When annealing ZnO NWs under argon, instead of air, significantly higher photoluminescence (PL) UV emission and relatively lower defects-related visible PL emission were obtained. At the same time, Ar-annealing rendered ZnO NWs with higher electrical conductivities, as observed from single NW measurements using conductive-atomic force microscopy. Furthermore, DSCs based on ZnO NWs annealed in argon were characterized by 50% higher photocurrents than those obtained from air-annealed ZnO. As a result 30% efficiency increases were systematically obtained when using argon as the annealing atmosphere. These results are discussed within the framework of a multiple trapping model for transport and charge transfer, taking into account differences in the defect concentration introduced during the annealing.

  • 8.
    Hao, Yan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Gabrielsson, Erik
    Royal Inst Technol KTH, Organ Chem, Ctr Mol Devices, Dept Chem Chem Sci & Engn, SE-10044 Stockholm, Sweden..
    Lohse, Peter William
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Yang, Wenxing
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    Royal Inst Technol KTH, Organ Chem, Ctr Mol Devices, Dept Chem Chem Sci & Engn, SE-10044 Stockholm, Sweden.;Dalian Univ Technol, State Key Lab Fine Chem, DUT KTH Joint Res Ctr Mol Devices, Dalian 116024, Peoples R China..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Peripheral Hole Acceptor Moieties on an Organic Dye Improve Dye-Sensitized Solar Cell Performance2015In: ADVANCED SCIENCE, Vol. 2, no 11, article id 1500174Article in journal (Refereed)
    Abstract [en]

    Investigation of charge transfer dynamics in dye-sensitized solar cells is of fundamental interest and the control of these dynamics is a key factor for developing more efficient solar cell devices. One possibility for attenuating losses through recombination between injected electrons and oxidized dye molecules is to move the positive charge further away from the metal oxide surface. For this purpose, a metal-free dye named E6 is developed, in which the chromophore core is tethered to two external triphenylamine (TPA) units. After photoinduced electron injection into TiO2, the remaining hole is rapidly transferred to a peripheral TPA unit. Electron-hole recombination is slowed down by 30% compared to a reference dye without peripheral TPA units. Furthermore, it is found that the added TPA moieties improve the electron blocking effect of the dye, retarding recombination of electrons from TiO2 to the cobalt-based electrolyte.

  • 9.
    Hao, Yan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Saygili, Yasemin
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, Stn 6, CH-1015 Lausanne, Switzerland..
    Cong, Jiayan
    KTH Royal Inst Technol, Sch Chem Sci & Engn, Dept Chem, Appl Phys Chem, Teknikringen 30, SE-10044 Stockholm, Sweden..
    Eriksson, Anna
    Yang, Wenxing
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zhang, Jinbao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Polanski, Enrico
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, Stn 6, CH-1015 Lausanne, Switzerland..
    Nonomura, Kazuteru
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, Stn 6, CH-1015 Lausanne, Switzerland..
    Zakeeruddin, Shaik Mohammed
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, Stn 6, CH-1015 Lausanne, Switzerland.;King Abdulaziz Univ, CEAMR, Jeddah 21589, Saudi Arabia..
    Gratzel, Michael
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, Stn 6, CH-1015 Lausanne, Switzerland..
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, Stn 6, CH-1015 Lausanne, Switzerland.;King Abdulaziz Univ, CEAMR, Jeddah 21589, Saudi Arabia..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Novel Blue Organic Dye for Dye-Sensitized Solar Cells Achieving High Efficiency in Cobalt-Based Electrolytes and by Co-Sensitization2016In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 8, no 48, p. 32797-32804Article in journal (Refereed)
    Abstract [en]

    Blue and green dyes as well as NIR-absorbing dyes have attracted great interest because of their excellent ability of absorbing the incident photons in the red and near-infrared range region. A novel blue D-pi-A dye (Dyenamo Blue), based on the diketopyrrolopyrrole (DPP)-core, has been designed and synthesized. Assembled with the cobalt bipyridine-based electrolytes, the device with Dyenamo Blue achieved a satisfying efficiency of 7.3% under one sun (AM1.5 G). The co-sensitization strategy was further applied on this blue organic dye together with a red D-pi-A dye (D35). The successful co-sensitization outperformed a panchromatic light absorption and improved the photocurrent density; this in addition to the open-circuit potential result in an efficiency of 8.7%. The extended absorption of the sensitization and the slower recombination reaction between the blue dye and TiO2 surface inhibited by the additional red sensitizer could be the two main reasons for the higher performance. In conclusion, from the results, the highly efficient cobalt-based DSSCs could be achieved with the co-sensitization between red and blue D-pi-A organic dyes with a proper design, which showed us the possibility of applying this strategy for future high-performance solar cells.

  • 10.
    Hao, Yan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Tian, Haining
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Cong, Jiayan
    Yang, Wenxing
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Bora, Ilkay
    Sun, Licheng
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Triphenylamine Groups Improve Blocking Behavior of Phenoxazine Dyes in Cobalt-Electrolyte-Based Dye-Sensitized Solar Cells2014In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 15, no 16, p. 3476-3483Article in journal (Refereed)
    Abstract [en]

    Novel phenoxazine dyes are successfully introduced as sensitizers into dye-sensitized solar cells (DSCs) with cobalt-based electrolyte. In sensitizers with triphenylamine (TPA) groups recombination from electrons in the TiO2 conduction band to the cobalt(III) species is suppressed. The effect of the steric properties of the phenoxazine sensitizers on the overall device performance and on recombination and regeneration processes is compared. Optimized DSCs sensitized with IB2 having two TPA groups in combination with tris(2,2'-bipyridyl) cobalt( II/III) yield efficiencies of 6.3 %, similar to that of IB3, which is equipped with mutiple alkoxy groups. TH310 with only one TPA group gives lower efficiency and open circuit voltage, while IB1 without TPA groups performs even worse. These results demonstrate that both TPA groups on the IB2 are needed for an efficient blocking effect. These results reveal a possible new role for TPA units in DSC sensitizer design.

  • 11.
    Hao, Yan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Yang, Wenxing
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zhang, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Jiang, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Mijangos, Edgar
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Molecular Biomimetics.
    Saygili, Yasemin
    Hammarström, Leif
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    A small electron donor in cobalt complex electrolyte significantly improves efficiency in dye-sensitized solar cells2016In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, article id 13934Article in journal (Refereed)
    Abstract [en]

    Photoelectrochemical approach to solar energy conversion demands a kinetic optimization of various light-induced electron transfer processes. Of great importance are the redox mediator systems accomplishing the electron transfer processes at the semiconductor/electrolyte interface, therefore affecting profoundly the performance of various photoelectrochemical cells. Here, we develop a strategy-by addition of a small organic electron donor, tris(4-methoxyphenyl)amine, into state-of-art cobalt tris(bipyridine) redox electrolyte-to significantly improve the efficiency of dye-sensitized solar cells. The developed solar cells exhibit efficiency of 11.7 and 10.5%, at 0.46 and one-sun illumination, respectively, corresponding to a 26% efficiency improvement compared with the standard electrolyte. Preliminary stability tests showed the solar cell retained 90% of its initial efficiency after 250 h continuous one-sun light soaking. Detailed mechanistic studies reveal the crucial role of the electron transfer cascade processes within the new redox system.

  • 12. Hao, Yan
    et al.
    Yang, Xichuan
    Cong, Jiayan
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    Engineering of highly efficient tetrahydroquinoline sensitizers for dye-sensitized solar cells2012In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 68, no 2, p. 552-558Article in journal (Refereed)
    Abstract [en]

    Four novel tetrahydroquinoline dyes by inserting isophorone and/or thiophene moieties as pi bridge between the electron donating unit of substituted tetrahydroquinoline and the electron withdrawing unit of cyano carboxylic acid have been synthesized and successfully applied to dye-sensitized solar cells. Among them, DSCs sensitized by HYTIC, which shows the simplest molecular structure, exhibit improved efficiency of 7.0%. This by now is the highest efficiency for the reported tetrahydroquinoline sensitizers and comparable to the performance of N719-sensitized solar cells under the conditions employed here.

  • 13.
    Hao, Yan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Yang, Xichuan
    Cong, Jiayan
    Jiang, Xiao
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    Photo-induced electron transfer study of D-pi-A sensitizers with different type of anchoring groups for dye-sensitized solar cells2012In: RSC Advances, ISSN 2046-2069, Vol. 2, no 14, p. 6011-6017Article in journal (Refereed)
    Abstract [en]

    A new D-pi-A organic dye HY102 with a lateral anchoring group and two reference dyes HY102-1 (using cyanoacrylic acid as an electron acceptor and the anchoring group) and HY102-2 (containing both cyanoacrylic acid and lateral carboxylic acid) have been synthesized. The optical and electrochemical test results from the three different styles of photosensitizers show that the excited electrons of the novel dye HY102 with lateral carboxylic acid group most probably are injected into the CB of TiO2 through the electron acceptor moiety close to the TiO2 surface by spatial transfer, not through the lateral anchoring group of the carboxylic acid. Research into the photo-induced electron transfer of the novel sensitizers with lateral anchoring system is reasonable and crucial for further improving efficiencies by modifying the molecular structures.

  • 14.
    Li, Hairong
    et al.
    Nanyang Technol Univ, Energy Res Inst NTU ERI N, Sch Mat Sci & Engn, Singapore 637553, Singapore.
    Koh, Teck Ming
    Nanyang Technol Univ, Energy Res Inst NTU ERI N, Sch Mat Sci & Engn, Singapore 637553, Singapore.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zhou, Feng
    Nanyang Technol Univ, Energy Res Inst NTU ERI N, Sch Mat Sci & Engn, Singapore 637553, Singapore.
    Abe, Yuichiro
    Nanyang Technol Univ, Energy Res Inst NTU ERI N, Sch Mat Sci & Engn, Singapore 637553, Singapore.
    Su, Haibin
    Nanyang Technol Univ, Energy Res Inst NTU ERI N, Sch Mat Sci & Engn, Singapore 637553, Singapore.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Grimsdale, Andrew C.
    Nanyang Technol Univ, Energy Res Inst NTU ERI N, Sch Mat Sci & Engn, Singapore 637553, Singapore.
    Comparative Studies on Rigid pi Linker-Based Organic Dyes: Structure-Property Relationships and Photovoltaic Performance2014In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 7, no 12, p. 3396-3406Article in journal (Refereed)
    Abstract [en]

    A series of six structurally correlated donor-pi bridge-acceptor organic dyes were designed, synthesized, and applied as sensitizers in dye-sensitized solar cells. Using the most widely studied donor (triarylamine) and cyclopenta[1,2-b:5,4-b’]dithiophene or cyclopenta[1,2-b: 5,4-b’] dithiophene[2’,1’:4,5]thieno[2,3-d] thiophene as pi spacers, their structure-property relationships were investigated in depth by photophysical techniques and theoretical calculations. It was found that the photovoltaic performance of these dyes largely depends on their electronic structures, which requires synergistic interaction between donors and acceptors. Increasing the electron richness of the donor or the elongation of pi-conjugated bridges does not necessarily lead to higher performance. Rather, it is essential to rationally design the dyes by balancing their light-harvesting capability with achieving suitable energy levels to guarantee unimpeded charge separation and transport.

  • 15.
    Liu, Peng
    et al.
    KTH Royal Inst Technol, Sch Chem Biotechnol & Hlth, Dept Chem, Ctr Mol Devices,Appl Phys Chem, SE-10044 Stockholm, Sweden.
    Wang, Linqin
    KTH Royal Inst Technol, Sch Chem Biotechnol & Hlth, Dept Chem, Ctr Mol Devices,Organ Chem, SE-10044 Stockholm, Sweden.
    Karlsson, Karl Martin
    KTH Royal Inst Technol, Sch Chem Biotechnol & Hlth, Dept Chem, Ctr Mol Devices,Appl Phys Chem, SE-10044 Stockholm, Sweden.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Gao, Jiajia
    KTH Royal Inst Technol, Sch Chem Biotechnol & Hlth, Dept Chem, Ctr Mol Devices,Appl Phys Chem, SE-10044 Stockholm, Sweden.
    Xu, Bo
    KTH Royal Inst Technol, Sch Chem Biotechnol & Hlth, Dept Chem, Ctr Mol Devices,Organ Chem, SE-10044 Stockholm, Sweden.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Licheng
    KTH Royal Inst Technol, Sch Chem Biotechnol & Hlth, Dept Chem, Ctr Mol Devices,Organ Chem, SE-10044 Stockholm, Sweden;Dalian Univ Technol, Inst Artificial Photosynth, State Key Lab Fine Chem, DUT KTH Joint Educ & Res Ctr Mol Devices, Dalian 116024, Peoples R China.
    Kloo, Lars
    KTH Royal Inst Technol, Sch Chem Biotechnol & Hlth, Dept Chem, Ctr Mol Devices,Appl Phys Chem, SE-10044 Stockholm, Sweden.
    Molecular Engineering of D-pi-A Type of Blue-Colored Dyes for Highly Efficient Solid-State Dye-Sensitized Solar Cells through Co-Sensitization2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 42, p. 35946-35952Article in journal (Refereed)
    Abstract [en]

    A novel blue-colored organic donor-pi-acceptor sensitizer, the so-called MKA16 dye, has been employed to construct solid-state dye-sensitized solar cells (ssDSSCs). Using 2,2',7-,7'-tetrakis(N,N-di-p-methoxyphenyl-amine) 9,9'-spirobifuorene (Spiro-OMeTAD) as hole-transport material, a good conversion efficiency of 5.8% was recorded for cells based on the MKA16 dye and a high photovoltage of 840 mV in comparison with 5.6% efficiency using the known (Dyenamo Blue) dye. By co-sensitization using the orange-colored D35 dye and MKA16 together, the solid-state solar cells showed an excellent efficiency of 7.5%, with a high photocurrent of 12.41 mA cm(-2) and open-circuit voltage of 850 mV. The results show that the photocurrent of ssDSSCs can be significantly improved by co-sensitization mainly attributed to the wider light absorption range contributing to the photocurrent. In addition, results from photo-induced absorption spectroscopy show that the dye regeneration is efficient in co-sensitized solar cells. The current results possible routes of improving the design of aesthetic and highly efficient ssDSSCs.

  • 16.
    Tian, Haining
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Oscarsson, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Gabrielsson, Erik
    KTH, Stockholm.
    Eriksson, Susanna K.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Lindblad, Rebecka
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Xu, Bo
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Gardner, James M.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Sun, Licheng
    KTH, Stockholm.
    Enhancement of p-Type Dye-Sensitized Solar Cell Performance by Supramolecular Assembly of Electron Donor and Acceptor2014In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 4, p. 4282-Article in journal (Refereed)
    Abstract [en]

    Supramolecular interactions based on porphyrin and fullerene derivatives were successfully adopted to improve the photovoltaic performance of p-type dye-sensitized solar cells (DSCs). Photoelectron spectroscopy (PES) measurements suggest a change in binding configuration of ZnTCPP after co-sensitization with C60PPy, which could be ascribed to supramolecular interaction between ZnTCPP and C60PPy. The performance of the ZnTCPP/C60PPy-based p-type DSC has been increased by a factor of 4 in comparison with the DSC with the ZnTCPP alone. At 560 nm, the IPCE value of DSCs based on ZnTCPP/C60PPy was a factor of 10 greater than that generated by ZnTCPP-based DSCs. The influence of different electrolytes on charge extraction and electron lifetime was investigated and showed that the enhanced V-oc from the Co2+/(3+)(dtbp)(3)-based device is due to the positive E-F shift of NiO.

  • 17.
    Tian, Lei
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Törndahl, Tobias
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Ling, Junzhong
    Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden.
    Pati, Palas Baran
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Kubart, Tomas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Sun, Junliang
    Stockholm Univ, Dept Mat & Environm Chem, S-10691 Stockholm, Sweden.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Tian, Haining
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Mechanistic Insights into Solid-State p-Type Dye-Sensitized Solar Cells2019In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 123, no 43, p. 26151-26160Article in journal (Refereed)
    Abstract [en]

    The study of p-type dye sensitized solar cells (p-DSCs) is appealing but challenging. Although the devices have been studied for 20 years, the light conversion efficiency lags far behind those of n-DSCs. Very recently, on the basis of a core-shell structure, a novel solid-state p-DSC (p-ssDSCs) has been fabricated, which showed great enhancement in open-circuit voltage and dye regeneration rate. To further improve the performance of such devices, charge diffusion, recombination process, and the main limiting factors have to be understood. In the present paper, core-shell p-ssDSCs with ZnO as an electron conductor were fabricated by atomic layer deposition. The charge transport time was determined to be ca. 0.1 ms, which is about 2 orders of magnitude faster than those of typical liquid devices with I-/I-3(-) as a redox mediator. As a consequence, the devices exhibit the highest reported charge diffusion coefficient (D-d)' among p-DSCs. It is ascribed to an electron-limiting diffusion process by the ambipolar diffusion model, suggesting a different charge-transport-determining mechanism in contrast to liquid p-DSCs. The charge recombination rate is 1-2 orders of magnitude slower than its charge transport time, mandating that the estimated charge collection efficiency is near unity. Detailed analysis of the incident photon-to-electron conversion efficiency suggests that the energy conversion efficiency in these p-ssDSCs is currently limited by a large fraction of dyes that is not fully electrically connected in the device.

  • 18.
    Yang, Wenxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Ghamgosar, Pedram
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Lulea Univ Technol, Dept Engn Sci & Math, Lulea, Sweden..
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Thermal Stability Study of Dye-Sensitized Solar Cells with Cobalt Bipyridyl-based Electrolytes2016In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 213, p. 879-886Article in journal (Refereed)
    Abstract [en]

    Dye-sensitized solar cells (DSSCs) with cobalt bipyridyl-based electrolytes can display higher solar cell performance than their iodide/triiodide counterpart. There is, however, little knowledge on their long term stability, which is a crucial aspect for potential commercial application. Herein, we studied the thermal stability of DSSCs using Co(bpy)(3)(2+/3+) redox electrolyte at 70 degrees C in the dark for 50 days, combining 3 different additives, 4-tert-butylpyridine (TBP), 1-methylimidazole (MBI) and 2,2'-bipyridyl (BPY), in a nonvolatile solvent 3-methoxypropionitrile (MPN). Significant voltage decreases were found for all the studied solar cells, with a mechanism involving both a positive shift of the conduction band edge potential of TiO2 and a decreased electron lifetime, characterized by time resolved transient modulation techniques. Furthermore electrochemical impedance spectroscopy and differential pulse voltammetry studies indicate that the stability of Co(bpy)(3)(3+) is limited, causing an increased diffusion resistance in the electrolyte, but, surprisingly, no substantial change of the short-circuit current density (Jsc) in the devices. Overall, the DSSCs fabricated with the addition of both MBI and BPY in the electrolyte show the highest stability, maintaining 96% of its initial efficiency after 50 days, resulting from the overall compensation effects between the open circuit voltage decrease and the Jsc increase. These results provide insights about the degradation mechanism and emphasize the importance of the stability of TiO2/dye/electrolyte interface for the device stability under thermal stress.

  • 19.
    Yang, Wenxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Vlachopoulos, Nick
    Ecole Polytech Fed Lausanne, FSB ISIC LSPM, Inst Chem Sci & Engn, Lab Photomol Sci, Chemin Alambics,Stn 6, CH-1015 Lausanne, Switzerland..
    Eriksson, Anna I. K.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Studies on the Interfacial Electric Field and Stark Effect at the TiO2/Dye/Electrolyte Interface2016In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 39, p. 22215-22224Article in journal (Refereed)
    Abstract [en]

    Interfaces of dye-sensitized TiO2 nanoparticles with electrolytes or hole conductors have been widely applied in photoelectrochemical cells. However, the fundamental understanding of their properties and function is still poor. Herein, we demonstrate that the spectral changes that occur in the-visible spectrum of dye-sensitized TiO2 films upon (a) Li+ titration, (b) potentiostatic electron accumulation in mesoporous TiO2, and (c) photoinduced electron injection into TiO2 can be explained by the Stark effect, which can then be used to characterize the change in the local electric field at the TiO2/dye/electrolyte interface. A quantitative analysis of the Stark effect indicates that the compact (Helmholtz) layer capacitance at the TiO2/dye/electrolyte interface strongly affects the strength of the local electric field. Systematic studies show that the Helmholtz layer capacitance depends strongly on the Li+ concentration and surface dye coverage but is independent of the concentrations of other electrolytic species and the light intensity. These results illustrate the potential of Stark spectroscopy for the in situ study of the TiO2/dye/electrolyte interfaces and provide substantial new insights into these widely applied interfaces related to photoelectrochemistry and other research fields.

  • 20.
    Yang, Wenxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Pazoki, Meysam
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Eriksson, Anna I. K.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    A key discovery at the TiO2/dye/electrolyte interface: slow local charge compensation and a reversible electric field2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 26, p. 16744-16751Article in journal (Refereed)
    Abstract [en]

    Dye-sensitized mesoporous TiO2 films have been widely applied in energy and environmental science related research fields. The interaction between accumulated electrons inside TiO2 and cations in the surrounding electrolyte at the TiO2/dye/electrolyte interface is, however, still poorly understood. This interaction is undoubtedly important for both device performance and fundamental understanding. In the present study, Stark effects of an organic dye, LEG4, adsorbed on TiO2 were well characterized and used as a probe to monitor the local electric field at the TiO2/dye/electrolyte interface. By using time-resolved photo- and potential-induced absorption techniques, we found evidence for a slow (t > 0.1 s) local charge compensation mechanism, which follows electron accumulation inside the mesoporous TiO2. This slow local compensation was attributed to the penetration of cations from the electrolyte into the adsorbed dye layer, leading to a more localized charge compensation of the electrons inside TiO2. Importantly, when the electrons inside TiO2 were extracted, a remarkable reversal of the surface electric field was observed for the first time, which is attributed to the penetrated and/or adsorbed cations now being charge compensated by anions in the bulk electrolyte. A cation electrosorption model is developed to account for the overall process. These findings give new insights into the mesoporous TiO2/dye/electrolyte interface and the electron-cation interaction mechanism. Electrosorbed cations are proposed to act as electrostatic trap states for electrons in the mesoporous TiO2 electrode.

  • 21.
    Yang, Wenxing
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Vlachopoulos, Nick
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Efficient dye regeneration at low driving force achieved in triphenylamine dye LEG4 and TEMPO redox mediator based dye-sensitized solar cells2015In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 17, no 24, p. 15868-15875Article in journal (Refereed)
    Abstract [en]

    Minimizing the driving force required for the regeneration of oxidized dyes using redox mediators in an electrolyte is essential to further improve the open-circuit voltage and efficiency of dye-sensitized solar cells (DSSCs). Appropriate combinations of redox mediators and dye molecules should be explored to achieve this goal. Herein, we present a triphenylamine dye, LEG4, in combination with a TEMPO-based electrolyte in acetonitrile (E-0 = 0.89 V vs. NHE), reaching an efficiency of up to 5.4% under one sun illumination and 40% performance improvement compared to the previously and widely used indoline dye D149. The origin of this improvement was found to be the increased dye regeneration efficiency of LEG4 using the TEMPO redox mediator, which regenerated more than 80% of the oxidized dye with a driving force of only similar to 0.2 eV. Detailed mechanistic studies further revealed that in addition to electron recombination to oxidized dyes, recombination of electrons from the conducting substrate and the mesoporous TiO2 film to the TEMPO+ redox species in the electrolyte accounts for the reduced short circuit current, compared to the state-of-the-art cobalt tris(bipyridine) electrolyte system. The diffusion length of the TEMPO-electrolyte based DSSCs was determined to be similar to 0.5 mu m, which is smaller than the similar to 2.8 mu m found for cobalt-electrolyte based DSSCs. These results show the advantages of using LEG4 as a sensitizer, compared to previously record indoline dyes, in combination with a TEMPO-based electrolyte. The low driving force for efficient dye regeneration presented by these results shows the potential to further improve the power conversion efficiency (PCE) of DSSCs by utilizing redox couples and dyes with a minimal need of driving force for high regeneration yields.

  • 22.
    Zhang, Jinbao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Yang, Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
    Mohammadi, Hajar
    Univ Isfahan, Dept Chem, Esfahan 8174673441, Iran.
    Vlachopoulos, Nick
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, CH G1 523, CH-1015 Lausanne, Switzerland.
    Sun, Licheng
    KTH Royal Inst Technol, Dept Chem Chem Sci & Engn, Ctr Mol Devices, Organ Chem, SE-10044 Stockholm, Sweden.
    Hagfeldt, Anders
    Ecole Polytech Fed Lausanne, Lab Photomol Sci, CH G1 523, CH-1015 Lausanne, Switzerland.
    Sheibani, Esmaeil
    Univ Isfahan, Dept Chem, Esfahan 8174673441, Iran.
    Electrochemically polymerized poly (3, 4-phenylenedioxythiophene) as efficient and transparent counter electrode for dye sensitized solar cells2019In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 300, p. 482-488Article in journal (Refereed)
    Abstract [en]

    A new conducting polymer poly (3, 4-phenylenedioxythiophene) is synthesized by the electrochemical polymerization technique with different solvents. We find that solvents used in electrochemical polymerization play important roles for the catalytic activity and morphology of the formed conducting polymers. The obtained poly (3, 4-phenylenedioxythiophene) is for the first time employed as counter electrode electrocatalyst in dye sensitized solar cells with cobalt-based electrolytes. We demonstrate that a polymer prepared from a mixed acetonitrile-dichloromethane solvent exhibit higher catalytic activity for redox reactions, as compared to that from a single solvent, dichloromethane. The devices based on this mixed solvent-based polymer from a mixed solvents show a high power conversion efficiency of 5.97%. An additional advantageous feature of the electrochemically polymerized poly (3, 4-phenylenedioxythiophene) for solar cell applications is the high transparency in the visible and nearinfrared region. We also investigate the beneficial effect of the poly (3, 4-phenylenedioxythiophene) layer thickness on device performance, and concluded that the series resistance and charge transfer resistance are greatly influenced by the thickness of polymer, as evidenced by electrochemical impedance spectroscopy measurements. The optimal thickness for poly (3, 4-phenylenedioxythiophene) is about 100 nm. Furthermore, the high catalytic activity and transparency of the new conducting polymer as counter electrode shows great promise for other optoelectronic applications.

  • 23.
    Zhang, Jinbao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Vlachopoulos, Nick
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, Stn 6, Chemin Alambics, CH-1015 Lausanne, Switzerland.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Holcombe, Thomas W
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, Swiss Fed Inst Technol,Stn 6, CH-1015 Lausanne, Switzerland.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Grätzel, Michael
    Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photon & Interfaces, Swiss Fed Inst Technol,Stn 6, CH-1015 Lausanne, Switzerland.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. Ecole Polytech Fed Lausanne, Inst Chem Sci & Engn, Lab Photomol Sci, Stn 6, Chemin Alambics, CH-1015 Lausanne, Switzerland.
    Efficient Blue-Colored Solid-State Dye-Sensitized Solar Cells: Enhanced Charge Collection by Using an in Situ Photoelectrochemically Generated Conducting Polymer Hole Conductor.2016In: ChemPhysChem, ISSN 1439-4235, E-ISSN 1439-7641, Vol. 17, no 10, p. 1441-1445Article in journal (Refereed)
    Abstract [en]

    A high power conversion efficiency (PCE) of 5.5 % was achieved by efficiently incorporating a diketopyrrolopyrrole-based dye with a conducting polymer poly(3,4-ethylenediothiophene) (PEDOT) hole-transporting material (HTM) that was formed in situ, compared with a PCE of 2.9 % for small molecular spiro-OMeTAD-based solid-state dye solar cells (sDSCs). The high PCE for PEDOT-based sDSCs is mainly attributed to the significantly enhanced charge-collection efficiency, as a result of the three-order-of-magnitude higher hole conductivity (0.53 S cm(-1) ) compared with that of the widely used low molecular weight HTM spiro-OMeTAD (3.5×10(-4)  S cm(-1) ).

  • 24.
    Zhang, Jinbao
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Yang, Lei
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Shen, Yang
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Park, Byung-Wook
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Johansson, Erik M. J.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Boschloo, Gerrit
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Kloo, Lars
    Gabrielsson, Erik
    Sun, Licheng
    Jarboui, Adel
    Perruchot, Christian
    Jouini, Mohamed
    Vlachopoulos, Nick
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Poly(3,4-ethylenedioxythiophene) Hole-Transporting Material Generated by Photoelectrochemical Polymerization in Aqueous and Organic Medium for All-Solid-State Dye-Sensitized Solar Cells2014In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 118, no 30, p. 16591-16601Article in journal (Refereed)
    Abstract [en]

    We applied organic donor-pi-acceptor (D-pi-A) sensitizers for photoelectrochemical polymerization (PEP) because of their appropriate energy levels and high light absorption. The polymerized conducting polymer PEDOT was used as hole conductor in all-solid-state dye-sensitized solar cells (ssDSCs). By combination of the D-pi-A sensitizers and the generated PEDOT from PEP of bis-EDOT in acetonitrile, the resulting device showed an average power conversion efficiency of 5.6%. Furthermore, the PEP in aqueous micellar electrolytic medium was also employed because of the ability to decrease oxidation potential of the precursor, thereby making the polymerization process easier. The latter method is a cost-effective and environmentally friendly approach. Using as hole conductor the so-obtained PEDOT from PEP of bis-EDOT in aqueous electrolyte, the devices exhibited impressive power conversion efficiency of 5.2%. To compare the properties of the generated polymer from bis-EDOT in these two PEP methods, electron lifetime, photoinduced absorption (PIA) spectra, and UV-vis-NIR spectra were measured. The results showed that PEDOT from organic PEP exhibits a delocalized conformation with high conductivity and a smooth and compact morphology; a rough morphology with high porosity and polymer structure of relatively shorter chains was assumed to be obtained from aqueous PEP. Therefore, better dye regeneration but faster charge recombination was observed in the device based on PEDOT from aqueous PEP of bis-EDOT. Subsequently, to extend the aqueous PEP approach in consideration of the ability to decrease the oxidation potential of the precursor, the easily available precursor EDOT was for the first time used for PEP in aqueous medium in a variant of the aforementioned procedure, and the device based on the so-obtained PEDOT shows a more than 70-fold increase in efficiency, 3.0%, over that based on the polymer generated from EDOT by PEP in organic media. It was demonstrated that aqueous micellar PEP with EDOT as monomer is an efficient strategy for generation of conducting polymer hole-transporting materials.

  • 25.
    Zhang, Wei
    et al.
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Liu, Peng
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Sadollahkhani, Azar
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Li, Yuanyuan
    KTH Royal Inst Technol, Wallenberg Wood Sci Ctr, Dept Fiber & Polymer Technol, SE-10044 Stockholm, Sweden..
    Zhang, Biaobiao
    KTH Royal Inst Technol, Dept Chem, Organ Chem, SE-10044 Stockholm, Sweden..
    Zhang, Fuguo
    KTH Royal Inst Technol, Dept Chem, Organ Chem, SE-10044 Stockholm, Sweden..
    Safdari, Majid
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry. KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Hua, Yong
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden.;Yunnan Univ, Sch Mat Sci & Engn, Kunming 650000, Yunnan, Peoples R China..
    Kloo, Lars
    KTH Royal Inst Technol, Dept Chem, Appl Phys Chem, SE-10044 Stockholm, Sweden..
    Investigation of Triphenylamine (TPA)-Based Metal Complexes and Their Application in Perovskite Solar Cells2017In: ACS OMEGA, ISSN 2470-1343, Vol. 2, no 12, p. 9231-9240Article in journal (Refereed)
    Abstract [en]

    Triphenylamine-based metal complexes were designed and synthesized via coordination to Ni(II), Cu(II), and Zn(II) using their respective acetate salts as the starting materials. The resulting metal complexes exhibit more negative energy levels (vs vacuum) as compared to 2,2', 7,7'-tetrakis(N, N-di-p-methoxyphenylamine)-9,9'-spirobifluorene (Spiro-OMeTAD), high hole extraction efficiency, but low hole mobilities and conductivities. Application of dopants typically used for Spiro-OMeTAD was not successful, indicating a more complicated mechanism of partial oxidation besides the redox potential. However, utilization as hole-transport material was successful, giving a highest efficiency of 11.1% under AM 1.5G solar illumination.

  • 26. Zhao, Jianghua
    et al.
    Yang, Xichuan
    Hao, Yan
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Cheng, Ming
    Tian, Jie
    Sun, Licheng
    Effect of Different Numbers of -CH2- Units on the Performance of Isoquinolinium Dyes2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 6, p. 3907-3914Article in journal (Refereed)
    Abstract [en]

    Three new dyes have been synthesized to investigate the influence of the distance between the electron acceptor and TiO2 surface on the performance of dye-sensitized solar cells (DSSCs). In these dyes, the isoquinolinium acceptor, with a -(CH2)(n) COOH anchoring group, and a functionalized triphenylamine donor are separated by an oligothiophene bridge. The physical and electrochemical properties of the dyes were investigated systematically. The results prove that different numbers of -CH2- units between the isoquinolinium acceptor and the carboxyl anchoring group have a less pronounced effect on the physical and electrochemical properties of these dyes. However, when applied in DSSCs, a sharp decrease in the short-circuit current (J(SC)) was observed with increasing numbers of -CH2- units. For example, the device containing the organic dye bearing three -CH2- units produced the lowest J(SC) of 7.94 mA.cm(-2). In contrast, the device containing the dye bearing only one -CH2- unit exhibited the highest J(SC) of 13.88 mA.cm(-2). The higher photocurrent obtained with the device incorporating the dye with one -CH2- unit resulted in a higher power conversion efficiency of 6.8%.

1 - 26 of 26
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