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Publications (10 of 57) Show all publications
Tian, L., Föhlinger, J., Zhang, Z.-B., Pati, P. B., Lin, J., Kubart, T., . . . Tian, H. (2018). Solid state p-type dye sensitized NiO-dye-TiO2 core-shell solar cells. Chemical Communications, 54(30), 3739-3742
Open this publication in new window or tab >>Solid state p-type dye sensitized NiO-dye-TiO2 core-shell solar cells
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2018 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 54, no 30, p. 3739-3742Article in journal (Refereed) Published
Abstract [en]

Solid state p-type dye sensitized NiO-dye-TiO2 core-shell solar cells with an organic dye PB6 were successfully fabricated for the first time. With Al2O3 as an inner barrier layer, the recombination process between injected holes in NiO and injected electrons in TiO2 was significantly suppressed and the charge transport time was also improved.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2018
National Category
Physical Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-352467 (URN)10.1039/c8cc00505b (DOI)000429592700013 ()29589009 (PubMedID)
Funder
Swedish Energy Agency, 43599-1
Available from: 2018-06-08 Created: 2018-06-08 Last updated: 2018-06-14Bibliographically approved
Tian, L., Föhlinger, J., Pati, P. B., Zhang, Z.-B., Lin, J., Yang, W., . . . Tian, H. (2018). Ultrafast dye regeneration in a core-shell NiO-dye-TiO2 mesoporous film. Physical Chemistry, Chemical Physics - PCCP, 20(1), 36-40
Open this publication in new window or tab >>Ultrafast dye regeneration in a core-shell NiO-dye-TiO2 mesoporous film
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2018 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 20, no 1, p. 36-40Article in journal (Refereed) Published
Abstract [en]

In this study, a core-shell NiO-dye-TiO2 mesoporous film was fabricated for the first time, utilizing atomic layer deposition technique and a newly designed triphenylamine dye. The structure of the film was confirmed by SEM, TEM, and EDX. Excitation of the dye led to efficient and fast charge separation, by hole injection into NiO, followed by an unprecedentedly fast dye regeneration (t1/2 [less-than-or-equal] 500 fs) by electron transfer to TiO2. The resulting charge separated state showed a pronounced transient absorption spectrum caused by the Stark effect, and no significant decay was found within 1.9 ns. This indicates that charge recombination between NiO and TiO2 is much slower than that between the NiO and the reduced dye in the absence of the TiO2 layer (t1/2 [approximate] 100 ps).

Place, publisher, year, edition, pages
The Royal Society of Chemistry, 2018
National Category
Natural Sciences Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-335974 (URN)10.1039/C7CP07088H (DOI)000418374800002 ()
Funder
Knut and Alice Wallenberg Foundation, 2011.0067Swedish Energy Agency, 43599-1
Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2018-03-14Bibliographically approved
Pati, P. B., Damas, G., Tian, L., Fernandes, D. L. A., Zhang, L., Bayrak Pehlivan, I., . . . Tian, H. (2017). An experimental and theoretical study of an efficient polymer nano-photocatalyst for hydrogen evolution. Energy & Environmental Science, 10(6), 1372-1376
Open this publication in new window or tab >>An experimental and theoretical study of an efficient polymer nano-photocatalyst for hydrogen evolution
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2017 (English)In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 10, no 6, p. 1372-1376Article in journal (Refereed) Published
Abstract [en]

In this work, we report a highly efficient organic polymer nano-photocatalyst for light driven proton reduction. The system renders an initial rate of hydrogen evolution up to 50 +/- 0.5 mmol g(-1) h(-1), which is the fastest rate among all other reported organic photocatalysts. We also experimentally and theoretically prove that the nitrogen centre of the benzothiadiazole unit plays a crucial role in the photocatalysis and that the Pdots structure holds a close to ideal geometry to enhance the photocatalysis.

Keywords
CATALYSTS; H-2; SYSTEM; ENVIRONMENTAL SCIENCES; CELLS; CONJUGATED POLYMERS; ENERGY & FUELS; ARTIFICIAL PHOTOSYNTHESIS; WATER; ENGINEERING, CHEMICAL; GENERATION; CHEMISTRY, MULTIDISCIPLINARY; VISIBLE-LIGHT
National Category
Polymer Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-332949 (URN)DOI: 10.1039/c7ee00751e (DOI)
Funder
Knut and Alice Wallenberg Foundation
Available from: 2017-11-02 Created: 2017-11-02 Last updated: 2017-11-13
D'Amario, L., Jiang, R., Cappel, U. B., Gibson, E. A., Boschloo, G., Rensmo, H., . . . Tian, H. (2017). Chemical and Physical Reduction of High Valence Ni States in Mesoporous NiO Film for Solar Cell Application.. ACS Applied Materials and Interfaces, 9(39), 33470-33477
Open this publication in new window or tab >>Chemical and Physical Reduction of High Valence Ni States in Mesoporous NiO Film for Solar Cell Application.
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2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 39, p. 33470-33477Article in journal (Refereed) Published
Abstract [en]

The most common material for dye-sensitized photocathodes is mesoporous NiO. We transformed the usual brownish NiO to be more transparent by reducing high valence Ni impurities. Two pretreatment methods have been used: chemical reduction by NaBH4 and thermal reduction by heating. The power conversion efficiency of the cell was increased by 33% through chemical treatment, and an increase in open-circuit voltage from 105 to 225 mV was obtained upon heat treatment. By optical spectroelectrochemistry, we could identify two species with characteristically different spectra assigned to Ni3+ and Ni4+. We suggest that the reduction of surface Ni3+ and Ni4+ to Ni2+ decreases the recombination reaction between holes on the NiO surface with the electrolyte. It also keeps the dye firmly on the surface, building a barrier for electrolyte recombination. This causes an increase in open-circuit photovoltage for the treated film.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-320184 (URN)10.1021/acsami.7b01532 (DOI)000412717600014 ()28368109 (PubMedID)
Funder
Swedish Energy Agency, 43599-1Knut and Alice Wallenberg Foundation, 2011.0067
Available from: 2017-04-17 Created: 2017-04-17 Last updated: 2018-01-10Bibliographically approved
Sorcar, S., Razzaq, A., Tian, H., Grimes, C. A. & In, S.-I. (2017). Facile electrochemical synthesis of anatase nano-architectured titanium dioxide films with reversible superhydrophilic behavior. Journal of Industrial and Engineering Chemistry, 46, 203-211
Open this publication in new window or tab >>Facile electrochemical synthesis of anatase nano-architectured titanium dioxide films with reversible superhydrophilic behavior
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2017 (English)In: Journal of Industrial and Engineering Chemistry, ISSN 1226-086X, E-ISSN 1876-794X, Vol. 46, p. 203-211Article in journal (Refereed) Published
Abstract [en]

In the present work we report a facile and readily-scalable electrochemical anodization technique for preparation of superhydrophilic TiO2 films having reversible wettability properties. The electrochemically anodized Titanium (Ti) foils manifest nanoscale topographical features, interconnected nanowebs and nanofibrils, that enhance both surface roughness and light absorption. After 5 min of UV illumination a water contact angle (WCA) of 4.8 degrees is measured for a 5 mu L deionized water droplet, while after 5 min of whitelight illumination the WCA is 3.2 degrees. Moreover, under UV illumination the superhydrophilic Ti foils exhibit self-cleaning properties. Key factors contributing to the superhydrophilic character include surface topology, and surface chemical reactions.

Keywords
Electrochemical anodization, Superhydrophilic, Nanowebs, Nanofibrils, Titanium dioxide, Surface topology
National Category
Chemical Engineering
Identifiers
urn:nbn:se:uu:diva-317580 (URN)10.1016/j.jiec.2016.10.032 (DOI)000393243500025 ()
Available from: 2017-03-22 Created: 2017-03-22 Last updated: 2017-11-29Bibliographically approved
Pati, P. B., Zhang, L., Philippe, B., Fernández-Terán, R., Ahmadi, S., Tian, L., . . . Tian, H. (2017). Insights into the Mechanism of a Covalently Linked Organic Dye-Cobaloxime Catalyst System for Dye-Sensitized Solar Fuel Devices. ChemSusChem, 10(11), 2480-2495
Open this publication in new window or tab >>Insights into the Mechanism of a Covalently Linked Organic Dye-Cobaloxime Catalyst System for Dye-Sensitized Solar Fuel Devices
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2017 (English)In: ChemSusChem, ISSN 1864-5631, E-ISSN 1864-564X, Vol. 10, no 11, p. 2480-2495Article in journal (Refereed) [Artistic work] Published
Abstract [en]

A covalently-linked organic dye-cobaloxime catalyst system is developed by facile click reaction for mechanistic studies and application in a dye sensitized solar fuel device based on mesoporous NiO. This system has been systematically investigated by photophysical measurements, density functional theory, time resolved fluorescence, transient absorption spectroscopy as well as photoelectron spectroscopy. The results show that irradiation of the dye-catalyst on NiO leads to ultrafast hole injection into NiO from the excited dye, followed by a fast electron transfer to reduce the catalyst unit. Moreover, they suggest that the dye undergoes structural changes in the excited state and that excitation energy transfer occurs between neighboring molecules. The photoelectrochemical experiments also show the hydrogen production by this system-based NiO photocathode. The axial chloride ligands of the catalyst are released during photocatalysis to create the active sites for proton reduction. A working mechanism of the dye-catalyst on photocathode is eventually proposed on the basis of this study.

Keywords
DSSFDs, electron transfer, Cobaloxime catalyst
National Category
Physical Chemistry
Research subject
Chemistry with specialization in Chemical Physics
Identifiers
urn:nbn:se:uu:diva-301412 (URN)10.1002/cssc.201700285 (DOI)000403005900021 ()
Available from: 2016-08-23 Created: 2016-08-23 Last updated: 2017-12-28Bibliographically approved
Besharat, Z., Alvarez-Asencio, R., Tian, H., Yu, S., Johnson, C. M., Gothelid, M. & Rutland, M. W. (2017). In-situ evaluation of dye adsorption on TiO2 using QCM. EPJ Photovoltaics, 8, Article ID 80401.
Open this publication in new window or tab >>In-situ evaluation of dye adsorption on TiO2 using QCM
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2017 (English)In: EPJ Photovoltaics, ISSN 2105-0716, Vol. 8, article id 80401Article in journal (Refereed) Published
Abstract [en]

We measured the adsorption characteristics of two organic dyes; triphenylamine-cyanoacrylic acid (TPA-C) and phenoxazine (MP13), on TiO2, directly in a solution based on quartz crystal microbalance (QCM). Monitoring the adsorbed amount as a function of dye concentration and during rinsing allows determination of the equilibrium constant and distinction between chemisorbed and physisorbed dye. The measured equilibrium constants are 0.8 mM(-1) for TPA-C and 2.4 mM(-1) for MP13. X-ray photoelectron spectroscopy was used to compare dried chemisorbed layers of TPA-C prepared in solution with TPA-C layers prepared via vacuum sublimation; the two preparation methods render similar spectra except a small contribution of water residues (OH) on the solution prepared samples. Quantitative Nanomechanical Mapping Atomic Force Microscopy (QNM-AFM) shows that physisorbed TPA-C layers are easily removed by scanning the tip across the surface. Although not obvious in height images, adhesion images clearly demonstrate removal of the dye.

Place, publisher, year, edition, pages
EDP SCIENCES S A, 2017
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-320219 (URN)10.1051/epjpv/2017002 (DOI)000396159700001 ()
Funder
Swedish Research CouncilKnut and Alice Wallenberg Foundation
Available from: 2017-04-18 Created: 2017-04-18 Last updated: 2017-11-29Bibliographically approved
Sheibani, E., Zhang, L., Liu, P., Xu, B., Mijangos, E., Boschloo, G., . . . Tian, H. (2016). A study of oligothiophene–acceptor dyes in p-type dye-sensitized solar cells. RSC Advances, 6(22), 18165-18177
Open this publication in new window or tab >>A study of oligothiophene–acceptor dyes in p-type dye-sensitized solar cells
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2016 (English)In: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, no 22, p. 18165-18177Article in journal (Refereed) Published
Abstract [en]

Two new dyes, E1 and E2, equipped with triphenylamine as the electron donor, oligothiophene as the linkerand different electron acceptor groups, have been designed and synthesized as photosensitizers for p-typedye-sensitized solar cells (p-DSCs). A systematic study of the effect of molecular structures on the observedphotophysical properties, the electron/hole recombination process, the overall performance and theinterfacial charge separation was carried out. Transient absorption spectroscopy (TAS) shows that the E1dye with a napthoilene-1,2-benzimidazole (NBI) unit as the acceptor has a longer lifetime in the reducedstate than the E2 dye with a malononitrile subunit on the NiO surface.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-280839 (URN)10.1039/c5ra26310g (DOI)000370717900043 ()
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg FoundationÅForsk (Ångpanneföreningen's Foundation for Research and Development), 14-452Stiftelsen Olle Engkvist Byggmästare
Available from: 2016-03-15 Created: 2016-03-15 Last updated: 2017-11-30
Antila, L. J., Ghamgosar, P., Maji, S., Tian, H., Ott, S. & Hammarström, L. (2016). Dynamics and Photochemical H-2 Evolution of Dye-NiO Photocathodes with a Biomimetic FeFe-Catalyst [Letter to the editor]. ACS ENERGY LETTERS, 1(6), 1106-1111
Open this publication in new window or tab >>Dynamics and Photochemical H-2 Evolution of Dye-NiO Photocathodes with a Biomimetic FeFe-Catalyst
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2016 (English)In: ACS ENERGY LETTERS, ISSN 2380-8195, Vol. 1, no 6, p. 1106-1111Article in journal, Letter (Refereed) Published
Abstract [en]

Mesoporous NiO films were cosensitized with a coumarin 343 dye and a proton reduction catalyst of the [Fe-2(CO)(6)(bdt)] (bdt = benzene-1,2-dithiolate) family. Femtosecond ultraviolet visible transient absorption experiments directly demonstrated subpicosecond hole injection into NiO from excited dyes followed by rapid (t(50%) similar to 6 ps) reduction of the catalyst on the surface with similar to 70% yield. The reduced catalyst was long-lived (2 mu s to 20 ms), which may allow protonation and a second reduction step of the catalyst to occur. A photo electrochemical device based on this photocathode produced H-2 with a Faradaic efficiency of similar to 50%. Fourier transform infrared spectroscopy and gas chromatography experiments demonstrated that the observed device deterioration with time was mainly due to catalyst degradation and desorption from the NiO surface. The insights gained from these mechanistic studies, regarding development of dye-catalyst cosensitized photocathodes, are discussed.

National Category
Physical Chemistry Nano Technology
Identifiers
urn:nbn:se:uu:diva-313538 (URN)10.1021/acsenergylett.6b00506 (DOI)000390086400005 ()
Funder
Swedish Research CouncilKnut and Alice Wallenberg FoundationSwedish Energy Agency
Available from: 2017-02-01 Created: 2017-01-20 Last updated: 2017-02-15Bibliographically approved
Hua, Y., Xu, B., Liu, P., Chen, H., Tian, H., Cheng, M., . . . Sun, L. (2016). High conductivity Ag-based metal organic complexes as dopant-free hole-transport materials for perovskite solar cells with high fill factors. Chemical Science, 7(4), 2633-2638
Open this publication in new window or tab >>High conductivity Ag-based metal organic complexes as dopant-free hole-transport materials for perovskite solar cells with high fill factors
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2016 (English)In: Chemical Science, ISSN 2041-6520, E-ISSN 2041-6539, Vol. 7, no 4, p. 2633-2638Article in journal (Refereed) Published
Abstract [en]

Hole-transport materials (HTMs) play an important role as hole scavenger materials in the most efficient perovskite solar cells (PSCs). Here, for the first time, two Ag-based metal organic complexes (HA1 and HA2) are employed as a new class of dopant-free hole-transport material for application in PSCs. These HTMs show excellent conductivity and hole-transport mobility. Consequently, the devices based on these two HTMs exhibit unusually high fill factors of 0.76 for HA1 and 0.78 for HA2, which are significantly higher than that obtained using spiro-OMeTAD (0.69). The cell based on HA1-HTM in its pristine form achieved a high power conversion efficiency of 11.98% under air conditions, which is comparable to the PCE of the cell employing the well-known doped spiro-MeOTAD (12.27%) under the same conditions. More importantly, their facile synthesis and purification without using column chromatography makes these new silver-based HTMs highly promising for future commercial applications of PSCs. These results provide a new way to develop more low-cost and high conductivity metal-complex based HTMs for efficient PSCs.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-288635 (URN)10.1039/c5sc03569d (DOI)000372614800020 ()
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg Foundation
Available from: 2016-05-04 Created: 2016-04-28 Last updated: 2017-11-30Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-6897-2808

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