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Bai, X., Yang, L., Hagfeldt, A., Johansson, E. & Jin, P. (2019). D35-TiO2 nano-crystalline film as a high performance visible-light photocatalyst towards the degradation of bis-phenol A. Chemical Engineering Journal, 355, 999-1010
Open this publication in new window or tab >>D35-TiO2 nano-crystalline film as a high performance visible-light photocatalyst towards the degradation of bis-phenol A
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2019 (English)In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 355, p. 999-1010Article in journal (Refereed) Published
Abstract [en]

Dye-sensitized photocatalytic suspension system for wastewater treatment is still limited in practice due to particle aggregation, fast charge carrier recombination, poor stability and recycling issue. In this study, we combine TiO2 nano-crystalline film with D35 organic dye to fabricate a new visible-light photocatalyst D35-TiO2, which exhibits excellent visible light absorption. Its transient photocurrent is almost 10 times higher than pure TiO2 under visible light illumination (lambda > 420 nm). Besides the well characterizations of the D35-TiO2 film, e.g., SEM, EDS, TEM, XRD, UV-Vis DRS, XPS, PL and I-T, degradation of bis-phenol A (BPA) is performed as the model reaction to test its photocatalytic activity. Meanwhile, we employ external bias in the reaction system to further enhance the photogenerated charge carrier separation, and improve the photocatalytic efficiency. Under the better experimental conditions of initial BPA concentration (5 mg/L), initial pH (pH 7), external bias (0.25 V) and sensitizer concentration (0.1 mM), BPA is almost completely degraded in 300 min, and the four intermediates are gradually mineralized. The ecotoxicity of BPA also decreases significantly after the photo-degradation. During the reaction, center dot O-2(-) plays a dominant role, meanwhile center dot OH and h(D35)(+) also contribute to the BPA degradation. After five cycles, the D35-TiO2 film still maintain the normal photocatalytic activity. Due to the high stability and recyclability, the D35-TiO2 nano-crystalline film provides a sustainable way for degrading micropollutants in wastewater.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2019
Keywords
Dye-sensitization, TiO2, Visible light, Nano-crystalline film
National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-363194 (URN)10.1016/j.cej.2018.08.061 (DOI)000445416900094 ()
Available from: 2018-10-18 Created: 2018-10-18 Last updated: 2018-10-18Bibliographically approved
Liu, J., Zhou, Q., Kyi Thein, N., Tian, L., Jia, D., Johansson, E. M. J. & Zhang, X. (2019). In situ growth of perovskite stacking layers for high-efficiency carbon-based hole conductor free perovskite solar cells. Journal of Materials Chemistry A, 7(22), 13777-13786
Open this publication in new window or tab >>In situ growth of perovskite stacking layers for high-efficiency carbon-based hole conductor free perovskite solar cells
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2019 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 7, no 22, p. 13777-13786Article in journal (Refereed) Published
Abstract [en]

The interfacial properties between a perovskite layer and carbon electrode are critical for the photovoltaic performance of carbon electrode-based perovskite solar cells (PSCs). Herein, a methylammonium lead mixed halide (MAPbIxBr3−x) perovskite layer is in situ grown on the top of a methylammonium lead iodide (MAPbI3) perovskite layer forming a MAPbI3/MAPbIxBr3−x perovskite stacking structure (PSS) to improve the interfacial properties at the perovskite/carbon electrode interface. The charge carrier dynamics in both the perovskite and the PSC device induced by the MAPbIxBr3−x perovskite stacking layer are studied using extensive characterization. The charge interfacial recombination at the perovskite/carbon electrode interface is significantly diminished using the PSS within the PSC, resulting in largely improved charge extraction and therefore high photovoltaic performance. The PSS-based PSC shows a power conversion efficiency of up to 16.2% (increased by 43% compared with that of a conventional MAPbI3-based PSC), which is among the highest efficiencies of carbon electrode-based hole conductor free PSCs. Meanwhile, the PSS-based PSC also exhibits good stability under both continuous illumination and storage under dark conditions. This work may provide a new avenue to fine tune the interfacial properties of carbon electrode-based PSCs for further improving their photovoltaic performance.

National Category
Materials Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-388769 (URN)10.1039/c9ta02772f (DOI)000470928800035 ()
Funder
Swedish Energy AgencySwedish Research Council FormasSwedish Research CouncilGöran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of Technology
Available from: 2019-07-05 Created: 2019-07-05 Last updated: 2019-07-05Bibliographically approved
Zhang, X., Cappel, U. B., Jia, D., Zhou, Q., Du, J., Sloboda, T., . . . Johansson, E. (2019). Probing and Controlling Surface Passivation of PbS Quantum Dot Solid for Improved Performance of Infrared Absorbing Solar Cells. Chemistry of Materials, 31(11), 4081-4091
Open this publication in new window or tab >>Probing and Controlling Surface Passivation of PbS Quantum Dot Solid for Improved Performance of Infrared Absorbing Solar Cells
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2019 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 11, p. 4081-4091Article in journal (Refereed) Published
Abstract [en]

Surface properties of colloidal quantum dots (CQDs) are critical for the transportation and recombination of the photoinduced charge carrier in CQD solar cells, therefore dominating the photovoltaic performance. Herein, PbS CQD passivated using liquid-state ligand exchange (LSLX) and solid-state ligand exchange (SSLX) strategies are in detail investigated using photoelectron spectroscopy (PES), and solar cell devices are prepared to understand the link between the CQD surface properties and the solar cell function. PES using different energies in the soft and hard Xray regime is applied to study the surface and bulk properties of the CQDs, and the results show more effective surface passivation of the CQDs prepared with the LSLX strategy and less formation of lead-oxide. The CQD solar cells prepared with LSLX strategy show higher performance, and the photoelectric measurements suggest that the recombination of photoinduced charges is reduced for the solar cell prepared with the LSLX approach. Meanwhile, the fabricated solar cells exhibit good stability. This work provides important insights into how to fine-tune the CQD surface properties by improving the CQD passivation, and how this is linked to further improvements of the device photovoltaic performance.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Materials Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-390215 (URN)10.1021/acs.chemmater.9b00742 (DOI)000471728200026 ()
Funder
Swedish Energy AgencySwedish Research Council FormasSwedish Research CouncilGöran Gustafsson Foundation for Research in Natural Sciences and MedicineStiftelsen Olle Engkvist ByggmästareÅForsk (Ångpanneföreningen's Foundation for Research and Development)
Available from: 2019-08-08 Created: 2019-08-08 Last updated: 2019-08-08Bibliographically approved
Karimipour, M., Bagheri, M., Johansson, E. & Molaei, M. (2018). Excellent growth of ZnS shell on Ag2S QDs using a photochemical-microwave irradiation approach and fabrication of their indoor QD thin film solar cells. Materials technology (New York, N.Y.), 33(12), 784-792
Open this publication in new window or tab >>Excellent growth of ZnS shell on Ag2S QDs using a photochemical-microwave irradiation approach and fabrication of their indoor QD thin film solar cells
2018 (English)In: Materials technology (New York, N.Y.), ISSN 1066-7857, E-ISSN 1753-5557, Vol. 33, no 12, p. 784-792Article in journal (Refereed) Published
Abstract [en]

In this report, a new two pots method using microwave-photochemical approaches was suggested for the fabrication of Ag2S@ZnS core-shells. UV-Vis and photoluminescence spectroscopies clearly proved the growth of ZnS shell on Ag2S cores. X-ray diffraction, Energy dispersive x-ray spectroscopy and transmission electron microscopy also indicated the formation of core-shell structure. To identify excellence growth of ZnS shell, Ag2S@ZnS core-shells were implemented for the fabrication of thin film solar cells. The fabricated cells showed a J-V character with 0.4%, 1 mA.cm(-2) and 0.43V and 54% as efficiency, J(SC), V-OC and fill factor, respectively. The cells showed also an increasing efficiency up to 0.8% upon the decrease of incident solar intensity to 10% of its standard. The results proved the cells are stable under sun light illumination that is promising for environmentally friendly fabrication of QD thin film solar cells.

Place, publisher, year, edition, pages
TAYLOR & FRANCIS LTD, 2018
Keywords
Ag2S@ZnS core-shells, Photoluminescence, Solar cells, Photochemical synthesis, Microwave irradiation
National Category
Materials Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-364486 (URN)10.1080/10667857.2018.1503781 (DOI)000443904600003 ()
Available from: 2018-10-29 Created: 2018-10-29 Last updated: 2018-10-29Bibliographically approved
Yang, L., Schölin, R., Gabrielsson, E., Boschloo, G., Rensmo, H., Sun, L., . . . Johansson, E. M. J. (2018). Experimental and Theoretical Investigation of the Function of 4-tert-Butyl Pyridine for Interface Energy Level Adjustment in Efficient Solid-State Dye-Sensitized Solar Cells. ACS Applied Materials and Interfaces, 10(14), 11572-11579
Open this publication in new window or tab >>Experimental and Theoretical Investigation of the Function of 4-tert-Butyl Pyridine for Interface Energy Level Adjustment in Efficient Solid-State Dye-Sensitized Solar Cells
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 14, p. 11572-11579Article in journal (Refereed) Published
Abstract [en]

4-tert-Butylpyridine (t-BP) is commonly used in solid state dye-sensitized solar cells (ssDSSCs) to increase the photovoltaic performance. In this report, the mechanism how t-BP functions as a favorable additive is investigated comprehensively. ssDSSCs were prepared with different concentrations of t-BP, and a clear increase in efficiency was observed up to a maximum concentration and for higher concentrations the efficiency thereafter decreases. The energy level alignment in the complete devices was measured using hard X-ray photoelectron spectroscopy (HAXPES). The results show that the energy levels of titanium dioxide are shifted further away from the energy levels of spiro-OMeTAD as the t-BP concentration is increased. This explains the higher photovoltage obtained in the devices with higher t-BP concentration. In addition, the electron lifetime was measured for the devices and the electron lifetime was increased when adding t-BP, which can be explained by the recombination blocking effect at the surface of TiO2. The results from the HAXPES measurements agree with those obtained from density functional theory calculations and give an understanding of the mechanism for the improvement, which is an important step for the future development of solar cells including t-BP.

Keywords
mesoporous, TiO2, photovoltaic, dye, solar energy
National Category
Physical Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-353206 (URN)10.1021/acsami.7b16877 (DOI)000430156000021 ()29560716 (PubMedID)
Funder
Swedish Energy AgencySwedish Research CouncilSwedish Research Council FormasEU, FP7, Seventh Framework Programme, 226716
Available from: 2018-06-13 Created: 2018-06-13 Last updated: 2018-06-13Bibliographically approved
Zhang, X., Öberg, V. A., Du, J., Liua, J. & Johansson, E. (2018). Extremely lightweight and ultra-flexible infrared light-converting quantum dot solar cells with high power-per-weight output using a solution-processed bending durable silver nanowire-based electrode. Energy & Environmental Science, 11(2), 354-364
Open this publication in new window or tab >>Extremely lightweight and ultra-flexible infrared light-converting quantum dot solar cells with high power-per-weight output using a solution-processed bending durable silver nanowire-based electrode
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2018 (English)In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 11, no 2, p. 354-364Article in journal (Refereed) Published
Abstract [en]

Lightweight and flexible solar cells are highly interesting materials for use in new applications, such as spacecraft, aircraft and personal pack load. PbS colloidal quantum dots (CQDs) exhibit a broad and strong light absorption spectrum covering the ultraviolet-visible-near infrared region, allowing for incorporation of very thin CQD films into solar cells with high power conversion efficiency (PCE) from solar light to electricity. Herein, we report an extremely lightweight and ultra-flexible CQD solar cell constructed on a polyethylene naphthalate substrate with a thickness of 1.3 mu m. A solution-processed Ag nanowire network with excellent mechanical, optical and electrical properties was prepared as the front-electrode in the solar cell. The thickness of the complete CQD solar cell is less than 2 mm, and similar to 10% PCE with a weight of 6.5 g m(-2) is achieved, resulting in a power-per-weight output of 15.2 W g(-1). The flexible solar cell possesses durable mechanical properties and maintains high-level photovoltaic performance under extreme deformation and after repeated compression-stretching deformation. Moreover, the flexible CQD solar cell shows impressive stability both under continuous illumination and after storage under ambient conditions. These results reveal that solution-processed CQDs are compatible with an ultra-flexible substrate for the construction of ultra-lightweight infrared light-converting CQD solar cells with possibilities for new exciting solar energy applications.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2018
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-349844 (URN)10.1039/c7ee02772a (DOI)000425283400013 ()
Funder
Göran Gustafsson Foundation for Research in Natural Sciences and MedicineSwedish Energy AgencySwedish Research Council FormasÅForsk (Ångpanneföreningen's Foundation for Research and Development)Swedish Research CouncilStiftelsen Olle Engkvist Byggmästare
Available from: 2018-05-03 Created: 2018-05-03 Last updated: 2018-05-03Bibliographically approved
Zhang, X., Jia, D., Hägglund, C., Öberg, V. A., Du, J., Liu, J. & Johansson, E. M. J. (2018). Highly photostable and efficient semitransparent quantum dot solar cells by using solution-phase ligand exchange. Nano Energy, 53, 373-382
Open this publication in new window or tab >>Highly photostable and efficient semitransparent quantum dot solar cells by using solution-phase ligand exchange
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2018 (English)In: Nano Energy, ISSN 2211-2855, E-ISSN 2211-3282, Vol. 53, p. 373-382Article in journal (Refereed) Published
Abstract [en]

For semitransparent solar cells (SSCs) the photovoltaic efficiency and the transparency are the two primary objectives for utilization in for example building integrated photovoltaics. Solution-processed PbS colloidal quantum dot (CQD) has strong light absorption in the ultraviolent region and possess the advantages of tunable bandgap in the visible and infrared region. Herein we report a PbS CQD-SSC with tunable infrared light absorption and high photostability by combining experimental studies and numerical theoretical simulations. Through fine-controlling the electro-optics in the CQD-SSC and by using a solution-phase ligand exchange for the CQD solid film deposition, the power loss in the device is significantly decreased, yielding a CQD-SSC with a power conversion efficiency of 8.4% and an average visible transmittance of 21.4%, respectively. After 540 h continuous 100 mW cm(-2) illumination the solar cell still shows similar to 85% of its initial power conversion efficiency, and then recovers to the initial performance after storage in dark. This work provides a strong progress and an approach toward the development of low-cost, highly efficient and stable semitransparent CQD solar cells. Meanwhile this study also provides insight and quantitative guidelines for further improving the SSC photovoltaic efficiency and transparency in general.

Keywords
Quantum dot, Ligand exchange, Semitransparent solar cells, Electro-optics, Energy loss
National Category
Physical Chemistry Materials Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-369607 (URN)10.1016/j.nanoen.2018.08.068 (DOI)000448994600041 ()
Funder
Swedish Energy AgencySwedish Research Council FormasSwedish Research CouncilÅForsk (Ångpanneföreningen's Foundation for Research and Development)Göran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologyStiftelsen Olle Engkvist Byggmästare
Available from: 2018-12-14 Created: 2018-12-14 Last updated: 2018-12-17Bibliographically approved
Öberg, V. A., Zhang, X., Johansson, M. B. & Johansson, E. M. J. (2018). Hot-Injection Synthesized Ag2S Quantum Dots with Broad Light Absorption and High Stability for Solar Cell Applications. CHEMNANOMAT, 4(12), 1223-1230
Open this publication in new window or tab >>Hot-Injection Synthesized Ag2S Quantum Dots with Broad Light Absorption and High Stability for Solar Cell Applications
2018 (English)In: CHEMNANOMAT, ISSN 2199-692X, Vol. 4, no 12, p. 1223-1230Article in journal (Refereed) Published
Abstract [en]

A hot-injection synthesis method was used to synthesize low-toxicity Ag2S colloidal quantum dots (CQDs) with strong and broad light absorption as an ultra-thin photo-absorber in CQD heterojunction solar cells. By using iodide and sulfur linkers it was possible to accomplish efficient charge carrier extraction, resulting in a high photocurrent due to the broad absorption spectrum. Transient photovoltage decay measurements were used to obtain information about trap states in the CQDs and the effect on the lifetime of the photoinduced carriers. The devices show very promising stability under constant long-term illumination and they are stable under ambient storage conditions with low losses to the performance over a period of over two months. These results show that Ag2S CQDs have high potential within solar cell applications, and point the direction for further improvements.

Keywords
energy conversion, hot-injection, quantum dots, silver sulfide, solar cells
National Category
Physical Chemistry Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-372703 (URN)10.1002/cnma.201800263 (DOI)000452048600005 ()
Funder
Swedish Energy AgencySwedish Research Council FormasSwedish Research CouncilÅForsk (Ångpanneföreningen's Foundation for Research and Development)
Available from: 2019-01-09 Created: 2019-01-09 Last updated: 2019-01-09Bibliographically approved
Zhang, X., Zhang, J., Phuyal, D., Du, J., Tian, L., Öberg, V. A., . . . Johansson, E. M. J. (2018). Inorganic CsPbI3 Perovskite Coating on PbS Quantum Dot for Highly Efficient and Stable Infrared Light Converting Solar Cells. Advanced Energy Materials, 8(6), Article ID 1702049.
Open this publication in new window or tab >>Inorganic CsPbI3 Perovskite Coating on PbS Quantum Dot for Highly Efficient and Stable Infrared Light Converting Solar Cells
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2018 (English)In: Advanced Energy Materials, ISSN 1614-6832, Vol. 8, no 6, article id 1702049Article in journal (Refereed) Published
Abstract [en]

Solution-processed colloidal quantum dot (CQD) solar cells harvesting the infrared part of the solar spectrum are especially interesting for future use in semitransparent windows or multilayer solar cells. To improve the device power conversion efficiency (PCE) and stability of the solar cells, surface passivation of the quantum dots is vital in the research of CQD solar cells. Herein, inorganic CsPbI3 perovskite (CsPbI3-P) coating on PbS CQDs with a low-temperature, solution-processed approach is reported. The PbS CQD solar cell with CsPbI3-P coating gives a high PCE of 10.5% and exhibits remarkable stability both under long-term constant illumination and storage under ambient conditions. Detailed characterization and analysis reveal improved passivation of the PbS CQDs with the CsPbI3-P coating, and the results suggest that the lattice coherence between CsPbI3-P and PbS results in epitaxial induced growth of the CsPbI3-P coating. The improved passivation significantly diminishes the sub-bandgap trap-state assisted recombination, leading to improved charge collection and therefore higher photovoltaic performance. This work therefore provides important insight to improve the CQD passivation by coating with an inorganic perovskite ligand for photovoltaics or other optoelectronic applications.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2018
Keywords
charge recombination, inorganic perovskite, quantum dots, solar cells, surface passivation
National Category
Physical Chemistry Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-348982 (URN)10.1002/aenm.201702049 (DOI)000426152400017 ()
Funder
Swedish Energy AgencySwedish Research CouncilSwedish Research Council Formas
Available from: 2018-04-26 Created: 2018-04-26 Last updated: 2018-10-26Bibliographically approved
Xu, L., Yang, L., Johansson, E., Wang, Y. & Jin, P. (2018). Photocatalytic activity and mechanism of bisphenol a removal over TiO2-x/rGO nanocomposite driven by visible light. Chemical Engineering Journal, 350, 1043-1055
Open this publication in new window or tab >>Photocatalytic activity and mechanism of bisphenol a removal over TiO2-x/rGO nanocomposite driven by visible light
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2018 (English)In: Chemical Engineering Journal, ISSN 1385-8947, E-ISSN 1873-3212, Vol. 350, p. 1043-1055Article in journal (Refereed) Published
Abstract [en]

In the present study, Ti3+ and oxygen vacancies (Ti3+/O-v) self-doped TiO2 and coupled with a reduced graphene oxide (rGO) nanocomposite (TiO2-x/rGO) was successfully synthesized via a facile hydrothermal-calcination method for the efficient degradation of bisphenol A (BPA) under visible light. The results of XPS, ERP and TEM analyses revealed that the presence of Ti3+/O-v in the lattice of TiO2-x/rGO leads to the narrowed band gap and enhanced visible light harvesting. The chemical bonds (TieOeC) between TiO2-x and rGO act as the channel for electron transfer, consequently resulting in the efficient charge separation, which was investigated and confirmed by such methods as PL spectra and time-resolved PL spectra. In addition, the coupling of TiO2-x and rGO could strongly suppress the aggregation of TiO2-x particles and therefore improve the adsorption of organic pollutants. For the synergistic effect of the three preeminent features mentioned above, TiO2-x/rGO exhibited a 6.16-, 2.92-and 2.55-fold faster reaction rate for BPA degradation than that of pristine TiO2, TiO2/rGO and TiO2-x, respectively. Moreover, the effects of the initial substrate concentration, initial solution pH, catalyst dosage and inorganic anions on BPA removal were also investigated in depth. EPR measurements indicated that center dot O-2(-) as the major oxidizing species, is responsible for the degradation of BPA. Next, the feasible pathway of BPA degradation by TiO2-x/rGO was proposed based on the analysis of intermediate products. Finally, the mechanism of the enhanced photocatalytic performance by TiO2-x/rGO under visible light was discussed. Based on these results, the TiO2-x/rGO nanocomposite could be an efficient and promising photocatalyst for the degradation of organic pollutants in water.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2018
Keywords
Endocrine disrupting chemicals, Bisphenol A, Ti3+ self-doped TiO2, TiO2-x/rGO nanocomposite, Visible-light photodegradation, Superoxide radicals
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-360171 (URN)10.1016/j.cej.2018.06.046 (DOI)000437093000104 ()
Available from: 2018-09-12 Created: 2018-09-12 Last updated: 2018-09-12Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-9358-8277

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