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Publications (10 of 16) Show all publications
Gao, J., El-Zohry, A. M., Trilaksana, H., Gabrielsson, E., Leandri, V., Ellis, H., . . . Kloo, L. (2018). Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells: An Electrolyte Effect. ACS Applied Materials and Interfaces, 10(31), 26241-26247
Open this publication in new window or tab >>Light-Induced Interfacial Dynamics Dramatically Improve the Photocurrent in Dye-Sensitized Solar Cells: An Electrolyte Effect
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 31, p. 26241-26247Article in journal (Refereed) Published
Abstract [en]

A significant increase in the photocurrent generation during light soaking for solar cells sensitized by the triphenylamine-based D-pi-A organic dyes (PD2 and LEG1) and mediated by cobalt bipyridine redox complexes has been observed and investigated. The crucial role of the electrolyte has been identified in the performance improvement. Control experiments based on a pretreatment strategy reveals TBP as the origin. The increase in the current and IPCE has been interpreted by the interfacial charge-transfer kinetics studies. A slow component in the injection kinetics was exposed for this system. This change explains the increase in the electron lifetime and collection efficiency. Photoelectron spectroscopic measurements show energy shifts at the dye/TiO2 interface, leading us to formulate a hypothesis with respect to an electrolyte induced dye reorganization at the surface.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
Keywords
dye-sensitized solar cells, electrolyte, interface, dynamics, light soaking
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:kth:diva-234184 (URN)10.1021/acsami.8b06897 (DOI)000441477800045 ()29996051 (PubMedID)2-s2.0-85049917640 (Scopus ID)
Note

QC 20181003

Available from: 2018-10-03 Created: 2018-10-03 Last updated: 2018-11-23Bibliographically approved
Sharmoukh, W., Cong, J., Gao, J., Liu, P., Quentin, D. & Kloo, L. (2018). Molecular Engineering of D-D-pi-A-Based Organic Sensitizers for Enhanced Dye-Sensitized Solar Cell Performance. ACS OMEGA, 3(4), 3819-3829
Open this publication in new window or tab >>Molecular Engineering of D-D-pi-A-Based Organic Sensitizers for Enhanced Dye-Sensitized Solar Cell Performance
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2018 (English)In: ACS OMEGA, ISSN 2470-1343, Vol. 3, no 4, p. 3819-3829Article in journal (Refereed) Published
Abstract [en]

A series of molecularly engineered and novel dyes WS1, WS2, WS3, and WS4, based on the D35 donor, 1-(4-hexylphenyl)-2,5-di(thiophen-2-yl)-1H-pyrrole and 4-(4-hexylphenyl)-4H-dithieno[3,2-b: 2', 3'-d] pyrrole as pi-conjugating linkers, were synthesized and compared to the well-known LEG4 dye. The performance of the dyes was investigated in combination with an electrolyte based on Co(II/III) complexes as redox shuttles. The electron recombination between the redox mediators in the electrolyte and the TiO2 interface decreases upon the introduction of 4-hexylybenzene entities on the 2,5-di(thiophen-2-yl)-1H-pyrrole and 4H-dithieno[3,2-b: 2', 3'-d] pyrrole linker units, probably because of steric hindrance. The open circuit photovoltage of WS1-, WS2-, WS3-, and WS4-based devices in combination with the Co(II/III)-based electrolyte are consistently higher than those based on a I-/I-3(-) electrolyte by 105, 147, 167, and 75 mV, respectively. The WS3-based devices show the highest power conversion efficiency of 7.4% at AM 1.5 G 100 mW/cm(2) illumination mainly attributable to the high open-circuit voltage (V-OC).

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-227229 (URN)10.1021/acsomega.8b00271 (DOI)000430200300022 ()2-s2.0-85045042845 (Scopus ID)
Note

QC 20150514

Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-05-14Bibliographically approved
Liu, P., Wang, L., Karlsson, K. M., Hao, Y., Gao, J., Xu, B., . . . Kloo, L. (2018). Molecular Engineering of D-pi-A Type of Blue-Colored Dyes for Highly Efficient Solid-State Dye-Sensitized Solar Cells through Co-Sensitization. ACS Applied Materials and Interfaces, 10(42), 35946-35952
Open this publication in new window or tab >>Molecular Engineering of D-pi-A Type of Blue-Colored Dyes for Highly Efficient Solid-State Dye-Sensitized Solar Cells through Co-Sensitization
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 42, p. 35946-35952Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2018
Keywords
solid-state dye-sensitized solar cell, blue-colored dye, co-sensitization, molecular engineering, D-pi-A dye
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-239097 (URN)10.1021/acsami.8b11405 (DOI)000448754500028 ()30260625 (PubMedID)2-s2.0-85054957061 (Scopus ID)
Note

QC 20181121

Available from: 2018-11-21 Created: 2018-11-21 Last updated: 2019-08-20Bibliographically approved
Gao, J., Fischer, A. C., Svensson, P. H. & Kloo, L. (2017). Crystallography as Forensic Tool for Understanding Electrolyte Degradation in Dye-sensitized Solar Cells. CHEMISTRYSELECT, 2(4), 1675-1680
Open this publication in new window or tab >>Crystallography as Forensic Tool for Understanding Electrolyte Degradation in Dye-sensitized Solar Cells
2017 (English)In: CHEMISTRYSELECT, ISSN 2365-6549, Vol. 2, no 4, p. 1675-1680Article in journal (Refereed) Published
Abstract [en]

The precipitation of solid compounds from model electrolytes for liquid dye-sensitized solar cells has a story to tell regarding decomposition processes to be expected in such systems. Of course, the crystal lattice energy for a specific crystalline compounds plays a role in what compound that will eventually precipitate, but the compounds nevertheless serve as indicators for what type of processes that take place in the solar cell electrolytes upon ageing. From the compounds isolated in this study we learn that both ligand exchange processes, double-salt precipitation and oxidation are degradation processes that should not be overlooked when formulating efficient and stable electrolytes for this type of electrochemical system.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2017
Keywords
Crystallography, Dye-sensitized solar cells, Forensics
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-205131 (URN)10.1002/slct.201601756 (DOI)000395533900043 ()
Note

QC 20170517

Available from: 2017-05-17 Created: 2017-05-17 Last updated: 2017-05-17Bibliographically approved
Bhagavathiachari, M., Elumalai, V., Gao, J. & Kloo, L. (2017). Polymer-doped molten salt mixtures as a new concept for electrolyte systems in dye-sensitized solar cells. ACS Omega, 2(10), 6570-6575
Open this publication in new window or tab >>Polymer-doped molten salt mixtures as a new concept for electrolyte systems in dye-sensitized solar cells
2017 (English)In: ACS Omega, ISSN 2470-1343, Vol. 2, no 10, p. 6570-6575Article in journal (Refereed) Published
Abstract [en]

A conceptually new polymer electrolyte for dye-sensitized solar cells is reported and investigated. The benefits of using this type of electrolyte based on ionic liquid mixtures (ILMs) and room temperature ionic liquids are highlighted. Impedance spectroscopy and transient electron measurements have been used to elucidate the background of the photovoltaic performance. Even though larger recombination losses were noted, the high ion mobility and conductivity induced in the ILMs by the added polymer result in enhanced overall conversion efficiencies.

Place, publisher, year, edition, pages
American Chemical Society, 2017
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-222934 (URN)10.1021/acsomega.7b00925 (DOI)000418744000030 ()2-s2.0-85032641455 (Scopus ID)
Note

QC 20180323

Available from: 2018-03-23 Created: 2018-03-23 Last updated: 2018-03-23Bibliographically approved
Chen, C., Cheng, M., Liu, P., Gao, J., Kloo, L. & Sun, L. (2016). Application of benzodithiophene based A-D-A structured materials in efficient perovskite solar cells and organic solar cells. Nano Energy, 23, 40-49
Open this publication in new window or tab >>Application of benzodithiophene based A-D-A structured materials in efficient perovskite solar cells and organic solar cells
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2016 (English)In: Nano Energy, ISSN 2211-2855, Vol. 23, p. 40-49Article in journal (Refereed) Published
Abstract [en]

In this work, we have designed and synthesized a novel molecular material, BDT-C1, in which the core unit, benzodithiophene (BDT), was functionalized by thiophene (TP) and benzo-[c][1,2,5]-thiadiazole (BTZ) derivatives to generate extended pi-conjugation. BDT-C1 shows high hole mobility and high conductivity in its pristine form, in combination with appropriate energy level alignment with respect to [CH3NH3]PbI3 and PC70BM, qualifying the material as a good candidate for application both in perovskite solar cells (PSCs) as dopant-free hole transport material (HTM) and in OSCs as donor material. The champion PSCs based on BDT-C1 show an average conversion efficiency (PCE) of 13.4% (scan forward: 13.9%; scan backward: PCE=12.9%, scan rate: 10 mV/s). Although the average efficiency obtained is slightly lower than that of reference devices based on the well-known doped HTM Spiro-OMeTAD (13.7%), the BDT-C1 based devices exhibit better stability. Moreover, BDT-C1 as a donor material in OSCs also shows good performance in combination with PC70BM as acceptor material, and an efficiency of 6.1% was obtained. The present results demonstrate that BDT-C1 works well as both donor material in OSCs as well as dopant-free HTMs for efficient PSCs.

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Perovskite solar cells, Dopant-free, Hole transport material, Organic solar cells, Donor material
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-187795 (URN)10.1016/j.nanoen.2016.03.007 (DOI)000375045900006 ()2-s2.0-84961135334 (Scopus ID)
Funder
Swedish Energy AgencySwedish Research CouncilKnut and Alice Wallenberg Foundation
Note

QC 20160531

Available from: 2016-05-31 Created: 2016-05-30 Last updated: 2017-08-15Bibliographically approved
Gao, J. (2016). Electrolyte-Based Dynamics: Fundamental Studies for Stable Liquid Dye-Sensitized Solar Cells. (Doctoral dissertation). KTH Royal Institute of Technology
Open this publication in new window or tab >>Electrolyte-Based Dynamics: Fundamental Studies for Stable Liquid Dye-Sensitized Solar Cells
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The long-term outdoor durability of dye-sensitized solar cells (DSSCs) is still a challenging issue for the large-scale commercial application of this promising photovoltaic technique. In order to study the degradation mechanism of DSSCs, ageing tests under selected accelerating conditions were carried out. The electrolyte is a crucial component of the device. The interactions between the electrolyte and other device components were unraveled during the ageing test, and this is the focus of this thesis. The dynamics and the underlying effects of these interactions on the DSSC performance were studied.

Co(bpy)32+/3+-mediated solar cells sensitized by triphenylamine-based organic dyes are systems of main interest. The changes with respect to the configuration of both labile Co(bpy)32+ and apparently inert Co(bpy)33+ redox complexes under different ageing conditions have been characterized, emphasizing the ligand exchange problem due to the addition of Lewis-base-type electrolyte additives and the unavoidable presence of oxygen. Both beneficial and adverse effects on the DSSC performance have been separately discussed in the short-term and long-term ageing tests. The stability of dye molecules adsorbed on the TiO2 surface and dissolved in the electrolyte has been studied by monitoring the spectral change of the dye, revealing the crucial effect of cation-based additives and the cation-dependent stability of the device photovoltage. The dye/TiO2 interfacial electron transfer kinetics were compared for the bithiophene-linked dyes before and after ageing in the presence of Lewis base additives; the observed change being related to the light-promoted and Lewis-base-assisted performance enhancement. The effect of electrolyte co-additives on passivating the counter electrode was also observed. The final chapter shows the effect of electrolyte composition on the electrolyte diffusion limitation from the perspectives of cation additive options, cation concentration and solvent additives respectively. Based on a comprehensive analysis, suggestions have been made regarding lithium-ion-free and polymer-in-salt strategies, and also regarding cobalt complex degradation and the crucial role of Lewis base additives. The fundamental studies contribute to the understanding of DSSC chemistry and provide a guideline towards achieving efficient and stable DSSCs.

Place, publisher, year, edition, pages
KTH Royal Institute of Technology, 2016. p. 171
Series
TRITA-CHE-Report, ISSN 1654-1081 ; 2016:27
Keywords
Dye-sensitized solar cells, Stability, Electrolyte, Cobalt redox couples, Additives
National Category
Physical Chemistry
Research subject
Chemistry
Identifiers
urn:nbn:se:kth:diva-187025 (URN)978-91-7729-013-1 (ISBN)
Public defence
2016-06-15, Sal K2, Teknikringen 28, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Funder
Swedish Energy AgencySwedish Research Council
Note

QC 20160517

Available from: 2016-05-17 Created: 2016-05-16 Last updated: 2017-05-03Bibliographically approved
Gao, J., Yang, W., Pazoki, M., Boschloo, G. & Kloo, L. (2015). Cation-Dependent Photostability of Co(II/III)-Mediated Dye-Sensitized Solar Cells. The Journal of Physical Chemistry C, 119(44), 24704-24713
Open this publication in new window or tab >>Cation-Dependent Photostability of Co(II/III)-Mediated Dye-Sensitized Solar Cells
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2015 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 119, no 44, p. 24704-24713Article in journal (Refereed) Published
Abstract [en]

The electrolyte composition has a significant effect on the performance and stability of cobalt-based, dye-sensitized solar cells (DSSCs). The stability of DSSCs incorporating Co(II/III) tris(bipyridine) redox mediator has been investigated over 1000 h under full solar irradiation (with UV cutoff) at a temperature of 60 °C, the main focus being on monitoring the photovoltaic performance of the device and analyzing the internal charge-transfer dynamics in the presence of different cation coadditives (preferably added as tetracyanoborate salts). A clear cation-dependence is shown, not only of the early light-induced performance but also of the long-term photostability of the photovoltage of the device. These light-induced changes, which are attributed to the promotion of electron injection and less electron recombination loss, by transient spectral and electrochemical studies at the TiO2/dye/electrolyte interface, indicate that the main cation effects involve the TiO2 surface electric field and energy-state distribution. By examining the stability of adsorbed and solvated dye during aging, it has been found that the dye photodegradation is probably responsible for the decline in the photovoltage and that this is extremely dependent on the nature of the cation coadditives in the electrolyte. It is therefore suggested that optimization of the electrolyte cation composition is essential for improving the stability of cobalt-based DSSCs.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2015
National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-181971 (URN)10.1021/acs.jpcc.5b06310 (DOI)000364435200003 ()2-s2.0-84946547956 (Scopus ID)
Funder
Swedish Research CouncilSwedish Energy Agency
Note

QC 20160212

Available from: 2016-02-12 Created: 2016-02-11 Last updated: 2017-11-30Bibliographically approved
Gabrielsson, E., Tian, H., Eriksson, S. K., Gao, J., Chen, H., Li, F., . . . Sun, L. (2015). Dipicolinic acid: a strong anchoring group with tunable redox and spectral behavior for stable dye-sensitized solar cells. Chemical Communications, 51(18), 3858-3861
Open this publication in new window or tab >>Dipicolinic acid: a strong anchoring group with tunable redox and spectral behavior for stable dye-sensitized solar cells
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2015 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 51, no 18, p. 3858-3861Article in journal (Refereed) Published
Abstract [en]

Dipicolinic acidwas investigated as a new anchoring group for DSSCs. A pilot dye (PD2) bearing this new anchoring group was found to adsorb significantly stronger to TiO2 than its cyanoacrylic acid analogue. The electrolyte composition was found to have a strong effect on the photoelectrochemical properties of the adsorbed dye in the device, allowing the dye LUMO energy to be tuned by 0.5 eV. Using a pyridine-free electrolyte, panchromatic absorption of the dye on TiO2 extending to 900 nm has been achieved. Solar cells using PD2 and a Co(bpy)(3) based electrolyte showed unique stability under simulated sunlight and elevated temperatures.

Keywords
Core-Level Shift, Electrolytes, Additives, Molecules
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-163486 (URN)10.1039/c4cc06432a (DOI)000349990600035 ()25655483 (PubMedID)2-s2.0-84923136577 (Scopus ID)
Funder
Knut and Alice Wallenberg FoundationSwedish Energy AgencyVINNOVASwedish Research Council
Note

QC 20150407

Available from: 2015-04-07 Created: 2015-04-07 Last updated: 2017-12-04Bibliographically approved
Gao, J., Bhagavathiachari, M. & Kloo, L. (2014). Long-term stability for cobalt-based dye-sensitized solar cells obtained by electrolyte optimization. Chemical Communications, 50(47), 6249-6251
Open this publication in new window or tab >>Long-term stability for cobalt-based dye-sensitized solar cells obtained by electrolyte optimization
2014 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 50, no 47, p. 6249-6251Article in journal (Refereed) Published
Abstract [en]

A significant improvement in the long-term stability for cobalt-based dye-sensitized solar cells (DSCs) under light-soaking conditions has been achieved by optimization of the composition of tris(2,2'-bipyridine) Co(II)/Co(III) electrolytes. The effects of component exchanges and changes were also studied during the optimization process.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-147440 (URN)10.1039/c4cc00698d (DOI)000336793100017 ()2-s2.0-84901044564 (Scopus ID)
Funder
Swedish Research CouncilSwedish Energy Agency
Note

QC 20140627

Available from: 2014-06-27 Created: 2014-06-27 Last updated: 2017-12-05Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5115-4593

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