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Hagfeldt, Anders
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Publications (10 of 315) Show all publications
Zhang, J., Xu, B., Yang, L., Ruan, C., Wang, L., Liu, P., . . . Johansson, E. (2018). The Importance of Pendant Groups on Triphenylamine-Based Hole Transport Materials for Obtaining Perovskite Solar Cells with over 20% Efficiency. Advanced Energy Materials, 18(2), Article ID 1701209.
Open this publication in new window or tab >>The Importance of Pendant Groups on Triphenylamine-Based Hole Transport Materials for Obtaining Perovskite Solar Cells with over 20% Efficiency
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2018 (English)In: Advanced Energy Materials, ISSN 1614-6832, Vol. 18, no 2, article id 1701209Article in journal (Refereed) Published
Abstract [en]

Tremendous progress has recently been achieved in the field of perovskite solar cells (PSCs) as evidenced by impressive power conversion efficiencies (PCEs); but the high PCEs of >20% in PSCs has so far been mostly achieved by using the hole transport material (HTM) spiro-OMeTAD; however, the relatively low conductivity and high cost of spiro-OMeTAD significantly limit its potential use in large-scale applications. In this work, two new organic molecules with spiro[fluorene-9,9-xanthene] (SFX)-based pendant groups, X26 and X36, have been developed as HTMs. Both X26 and X36 present facile syntheses with high yields. It is found that the introduced SFX pendant groups in triphenylamine-based molecules show significant influence on the conductivity, energy levels, and thin-film surface morphology. The use of X26 as HTM in PSCs yields a remarkable PCE of 20.2%. In addition, the X26-based devices show impressive stability maintaining a high PCE of 18.8% after 5 months of aging in controlled (20%) humidity in the dark. We believe that X26 with high device PCEs of >20% and simple synthesis show a great promise for future application in PSCs, and that it represents a useful design platform for designing new charge transport materials for optoelectronic applications.

Keywords
high efficiency, hole transport materials, perovskites, photovoltaic devices, solar cells
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-336199 (URN)10.1002/aenm.201701209 (DOI)000419864800001 ()
Funder
Swedish Energy AgencyÅForsk (Ångpanneföreningen's Foundation for Research and Development)Swedish Research CouncilSwedish Research Council Formas
Available from: 2017-12-12 Created: 2017-12-12 Last updated: 2018-02-14Bibliographically approved
Pazoki, M., Cappel, U. B., Johansson, E. M. J., Hagfeldt, A. & Boschloo, G. (2017). Characterization techniques for dye-sensitized solar cells. Energy & Environmental Science, 10(3), 672-709
Open this publication in new window or tab >>Characterization techniques for dye-sensitized solar cells
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2017 (English)In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 10, no 3, p. 672-709Article, review/survey (Refereed) Published
Abstract [en]

Dye-sensitized solar cells (DSCs) have been widely studied in the last two decades and start to be commercialized in the photovoltaic market. Comprehensive characterization is needed to fully understand and optimize the device performance and stability. In this review, we summarize different characterization methods for dye-sensitized solar cells with liquid redox electrolytes or solid state hole transporting materials, most of which can also be used for similar devices such as perovskite based thin film solar cells. Limitations and advantages of relevant methods for studying the energy levels and time scales involved in charge transfer processes as well as charge transport related characteristic lengths are discussed. A summary of recent developments in DSCs and the importance of measured parameters for the device optimization procedure are mentioned at the end.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2017
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-320102 (URN)10.1039/c6ee02732f (DOI)000396430700002 ()
Available from: 2017-04-26 Created: 2017-04-26 Last updated: 2017-04-26Bibliographically approved
Philippe, B., Saliba, M., Correa-Baena, J.-P., Cappel, U. B., Turren-Cruz, S.-H., Grätzel, M., . . . Rensmo, H. (2017). Chemical Distribution of Multiple Cation (Rb+, Cs+, MA+, and FA+) Perovskite Materials by Photoelectron Spectroscopy. Chemistry of Materials, 29(8), 3589-3596
Open this publication in new window or tab >>Chemical Distribution of Multiple Cation (Rb+, Cs+, MA+, and FA+) Perovskite Materials by Photoelectron Spectroscopy
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2017 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 8, p. 3589-3596Article in journal (Refereed) Published
Abstract [en]

Lead-based mixed perovskite materials have emerged in the last couple of years as promising photovoltaic materials. Recently, it was shown that improved material stability can be achieved by incorporating small amounts of inorganic cations (Cs+  and Rb+ ), partially replacing the more common organic cations (e.g., methylammonium, MA, and formamidinium, FA). Especially, a mixed cation composition containing Rb+ , Cs+ , MA+ , and FA+  was recently shown to have benefi cial optoelectronic properties and was stable at elevated temperature. This work focuses on the composition of this material using synchrotron-based photoelectron spectroscopy. Diff erent probing depths were considered by changing the photon energy of the X-ray source providing insights on the chemical composition and the chemical distribution near the surface of the samples. Perovskite materials containing two, three, or four monovalent cations were analyzed and compared.

The presence of Cs and Rb was observed both at the sample surface and toward the bulk, and we found that in the presence of three or four cations, less unreacted PbI2  remains in the sample. Interestingly, Rb and Cs appear to act jointly resulting in a different cation depth profile compared to that of the triple counterparts. Our findings provide significant understanding of the intricate depth-dependent chemical composition in perovskite materials using the common practice of cation mixing.

National Category
Energy Systems
Identifiers
urn:nbn:se:uu:diva-321392 (URN)10.1021/acs.chemmater.7b00126 (DOI)000400233100028 ()
Funder
Swedish Research CouncilSwedish Energy AgencySwedish Foundation for Strategic Research
Available from: 2017-05-04 Created: 2017-05-04 Last updated: 2017-11-17Bibliographically approved
Zhang, J., Xu, B., Yang, L., Mingorance, A., Ruan, C., Hua, Y., . . . Johansson, E. (2017). Incorporation of Counter Ions in Organic Molecules: New Strategy in Developing Dopant-Free Hole Transport Materials for Efficient Mixed-Ion Perovskite Solar Cells. ADVANCED ENERGY MATERIALS, 7(14), Article ID 1602736.
Open this publication in new window or tab >>Incorporation of Counter Ions in Organic Molecules: New Strategy in Developing Dopant-Free Hole Transport Materials for Efficient Mixed-Ion Perovskite Solar Cells
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2017 (English)In: ADVANCED ENERGY MATERIALS, ISSN 1614-6832, Vol. 7, no 14, article id 1602736Article in journal (Refereed) Published
Abstract [en]

Hole transport matertial (HTM) as charge selective layer in perovskite solar cells (PSCs) plays an important role in achieving high power conversion efficiency (PCE). It is known that the dopants and additives are necessary in the HTM in order to improve the hole conductivity of the HTM as well as to obtain high efficiency in PSCs, but the additives can potentially induce device instability and poor device reproducibility. In this work a new strategy to design dopant-free HTMs has been presented by modifying the HTM to include charged moieties which are accompanied with counter ions. The device based on this ionic HTM X44 dos not need any additional doping and the device shows an impressive PCE of 16.2%. Detailed characterization suggests that the incorporated counter ions in X44 can significantly affect the hole conductivity and the homogeneity of the formed HTM thin film. The superior photovoltaic performance for X44 is attributed to both efficient hole transport and effective interfacial hole transfer in the solar cell device. This work provides important insights as regards the future design of new and efficient dopant free HTMs for photovotaics or other optoelectronic applications.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2017
National Category
Physical Chemistry Engineering and Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-332853 (URN)10.1002/aenm.201602736 (DOI)000405839400018 ()
Funder
Swedish Energy AgencyÅForsk (Ångpanneföreningen's Foundation for Research and Development)Swedish Research CouncilSwedish Research Council Formas
Available from: 2017-11-08 Created: 2017-11-08 Last updated: 2017-12-14Bibliographically approved
Pazoki, M., Jacobsson, J. T., Cruz, S., Johansson, M. B., Imani, R., Kullgren, J., . . . Boschloo, G. (2017). Photon Energy-Dependent Hysteresis Effects in Lead Halide Perovskite Materials. The Journal of Physical Chemistry C, 121(47), 26180-26187
Open this publication in new window or tab >>Photon Energy-Dependent Hysteresis Effects in Lead Halide Perovskite Materials
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2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 47, p. 26180-26187Article in journal (Refereed) Published
Abstract [en]

Lead halide perovskites have a range of spectacular properties and interesting phenomena and are a serious candidate for the next generation of photovoltaics with high efficiencies and low fabrication costs. An interesting phenomenon is the anomalous hysteresis often seen in current-voltage scans, which complicates accurate performance measurements but has also been explored to obtain a more comprehensive understanding of the device physics. Herein, we demonstrate a wavelength and illumination intensity dependency of the hysteresis in state-of-the-art perovskite solar cells with 18% power conversion efficiency (PCE), which gives new insights into ion migration. The perovskite devices show lower hysteresis under illumination with near band edge (red) wavelengths compared to more energetic (blue) excitation. This can be rationalized with thermalization-assisted ion movement or thermalization-assisted vacancy generation. These explanations are supported by the dependency of the photovoltage decay with illumination time and excitation wavelength, as well as by impedance spectroscopy. The suggested mechanism is that high-energy photons create hot charge carriers that either through thermalization can create additional vacancies or by release of more energetic phonons play a role in overcoming the activation energy for ion movement. The excitation wavelength dependency of the hysteresis presented here gives valuable insights into the photophysics of the lead halide perovskite solar cells.

National Category
Physical Chemistry Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-334350 (URN)10.1021/acs.jpcc.7b06775 (DOI)000417228500005 ()
Funder
ÅForsk (Ångpanneföreningen's Foundation for Research and Development), 43294-1StandUp
Available from: 2017-11-22 Created: 2017-11-22 Last updated: 2018-03-08Bibliographically approved
Hao, Y., Yang, W., Zhang, L., Jiang, R., Mijangos, E., Saygili, Y., . . . Boschloo, G. (2016). A small electron donor in cobalt complex electrolyte significantly improves efficiency in dye-sensitized solar cells. Nature Communications, 7, Article ID 13934.
Open this publication in new window or tab >>A small electron donor in cobalt complex electrolyte significantly improves efficiency in dye-sensitized solar cells
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2016 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 7, article id 13934Article in journal (Refereed) Published
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.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-310194 (URN)10.1038/ncomms13934 (DOI)000390223200001 ()
Funder
Swedish Research CouncilSwedish Energy AgencyKnut and Alice Wallenberg FoundationStiftelsen Olle Engkvist Byggmästare
Note

Yan Hao and Wenxing Yang contributed equally to this work.

Available from: 2016-12-12 Created: 2016-12-12 Last updated: 2018-08-16Bibliographically 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
Sveinbjörnsson, K., Aitola, K., Zhang, J., Johansson, M. B., Zhang, X., Correa-Baena, J.-P., . . . Johansson, E. M. J. (2016). Ambient air-processed mixed-ion perovskites for high-efficiency solar cells. Journal of Materials Chemistry A, 4(42), 16536-16545
Open this publication in new window or tab >>Ambient air-processed mixed-ion perovskites for high-efficiency solar cells
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2016 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 4, no 42, p. 16536-16545Article in journal (Refereed) Published
Abstract [en]

Mixed-ion (FAPbI(3))(1-x)(MAPbBr(3))(x) perovskite solar cells have achieved power conversion efficiencies surpassing 20%. However, in order to obtain these high efficiencies the preparation is performed in a controlled inert atmosphere. Here, we report a procedure for manufacturing highly efficient solar cells with a mixed-ion perovskite in ambient atmosphere. By including a heating step at moderate temperatures of the mesoporous titanium dioxide substrates, and spin-coating the perovskite solution on the warm substrates in ambient air, a red intermediate phase is obtained. Annealing the red phase at 100 degrees C results in a uniform and crystalline perovskite film, whose thickness is dependent on the substrate temperature prior to spin-coating. The temperature was optimized between 20 and 100 degrees C and it was observed that 50 degrees C substrate temperature yielded the best solar cell performances. The average efficiency of the best device was 17.6%, accounting for current-voltage (I-V) measurement hysteresis, with 18.8% performance in the backward scan direction and 16.4% in the forward scan direction. Our results show that it is possible to manufacture high-efficiency mixed-ion perovskite solar cells under ambient conditions, which is relevant for large-scale and low-cost device manufacturing processing.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-310043 (URN)10.1039/c6ta06912f (DOI)000387166900031 ()
Funder
Göran Gustafsson Foundation for promotion of scientific research at Uppala University and Royal Institute of TechnologySwedish Energy AgencyÅForsk (Ångpanneföreningen's Foundation for Research and Development)Swedish Research Council FormasSwedish Research Council
Available from: 2016-12-09 Created: 2016-12-09 Last updated: 2018-01-31Bibliographically approved
Aitola, K., Sveinbjörnsson, K., Correa-Baena, J.-P., Kaskela, A., Abate, A., Tian, Y., . . . Boschloo, G. (2016). Carbon nanotube-based hybrid hole-transporting material and selective contact for high efficiency perovskite solar cells. Energy & Environmental Science, 9(2), 461-466
Open this publication in new window or tab >>Carbon nanotube-based hybrid hole-transporting material and selective contact for high efficiency perovskite solar cells
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2016 (English)In: Energy & Environmental Science, ISSN 1754-5692, E-ISSN 1754-5706, Vol. 9, no 2, p. 461-466Article in journal (Refereed) Published
Abstract [en]

We demonstrate a high efficiency perovskite solar cell with a hybrid hole-transporting material-counter electrode based on a thin single-walled carbon nanotube (SWCNT) film and a drop-cast 2,2,7,-7-tetrakis(N, N-di-p-methoxyphenylamine)-9,90-spirobifluorene (Spiro-OMeTAD) hole-transporting material (HTM). The average efficiency of the solar cells was 13.6%, with the record cell yielding 15.5% efficiency. The efficiency of the reference solar cells with spin-coated Spiro-OMeTAD hole-transportingmaterials (HTMs) and an evaporated gold counter electrode was 17.7% (record 18.8%), that of the cells with only a SWCNT counter electrode (CE) without additional HTM was 9.1% (record 11%) and that of the cells with gold deposited directly on the perovskite layer was 5% (record 6.3%). Our results show that it is possible to manufacture high efficiency perovskite solar cells with thin film (thickness less than 1 mu m) completely carbon-based HTMCEs using industrially upscalable manufacturing methods, such as press-transferred CEs and drop-cast HTMs.

National Category
Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-280914 (URN)10.1039/c5ee03394b (DOI)000369744500010 ()
Funder
Swedish Energy AgencySwedish Research CouncilKnut and Alice Wallenberg FoundationStandUpEU, FP7, Seventh Framework Programme, 604472
Available from: 2016-03-16 Created: 2016-03-16 Last updated: 2018-01-31Bibliographically approved
Freitag, M., Giordano, F., Yang, W., Pazoki, M., Hao, Y., Zietz, B., . . . Boschloo, G. (2016). Copper Phenanthroline as a Fast and High-Performance Redox Mediator for Dye-Sensitized Solar Cells. The Journal of Physical Chemistry C, 120(18), 9595-9603
Open this publication in new window or tab >>Copper Phenanthroline as a Fast and High-Performance Redox Mediator for Dye-Sensitized Solar Cells
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2016 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 120, no 18, p. 9595-9603Article in journal (Refereed) Published
Abstract [en]

The most commonly used redox mediators in dye-sensitized solar cells (DSCs), iodide/triiodide and cobalt trisbipyridine ([Co(bpy)(3)](2+/3+)), were successfully replaced by bis (2,9-dimethy1-1,10-phenanthroline) copp er (I/H) ([Cu(dmp)(2)](1+/2+)). The use of the copper complex based electrolyte led to an exceptionally high photovoltaic performance of 8.3% for LEG4-sensitized TiO2 solar cells, with a remarkably high open-circuit potential of above 1.0 V at 1000 W m(-2) under AM1.5G conditions. The copper complex based redox electrolyte has higher diffusion coefficients and is considerably faster in dye regeneration than comparable cobalt trisbipyridine based electrolytes. A driving force for dye regeneration of only 0.2 eV is sufficient to obtain unit yield, pointing to new possibilities for improvement in DSC efficiencies. The interaction of the excited dye with components of the electrolyte was monitored using steady-state emission measurements and time-correlated single-photon counting (TC-SPC). Our results indicate bimolecular reductive quenching of the excited LEG4 dye by the [Cu(dmp)(2)](2+) complex through a dynamic mechanism. Excited-state dye molecules can readily undergo bimolecular electron transfer with a suitable donor molecule. In DSCs this process can occur when the excited dye is unable to inject electrons into the TiO2. With a high electrolyte concentration the excited dye can be intercepted with an electron from the electrolyte resulting in the reduced state of the dye. Quenching of the reduced dye by the electrolyte competes with electron injection and results in a lower photocurrent. Quenching of excited LEG4 by complexes of [Cu(dmp)(2)](+), [Co(bpy)(3)](2+), and [Co(bpy)(3)](3+) followed a static mechanism, due ground-state dye-quencher binding. Inhibition of unwanted quenching processes by structural modifications may open ways to further increase the overall efficiency.

National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-298095 (URN)10.1021/acs.jpcc.6b01658 (DOI)000375969000007 ()
Funder
Swedish Energy AgencySwedish Research CouncilStandUp
Available from: 2016-06-29 Created: 2016-06-29 Last updated: 2017-11-28Bibliographically approved
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