Change search
Link to record
Permanent link

Direct link
BETA
Publications (10 of 17) Show all publications
Blazinic, V., Ericsson, L., Levine, I., Hansson, R., Opitz, A. & Moons, E. (2019). Impact of intentional photo-oxidation of a donor polymer and PC70BM on solar cell performance. Physical Chemistry, Chemical Physics - PCCP, 21, 22259-22271
Open this publication in new window or tab >>Impact of intentional photo-oxidation of a donor polymer and PC70BM on solar cell performance
Show others...
2019 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 21, p. 22259-22271Article in journal (Refereed) Published
Abstract [en]

A short lifetime is the main factor hindering the wider implementation of low-cost organic photovoltaics in large-area and outdoor applications. Ingress of oxygen and water vapour through non-ideal encapsulation layers is a known cause of degradation for polymer/fullerene based solar cells. To better understand the origin of this performance degradation, we study the effect of intentional exposure of the photo-active layer to simulated sunlight (AM1.5) in air both on the solar cell performance and on the molecular semiconductor materials. Cathode-free thin films of a blend of the electron donor polymer poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1) and the electron acceptor fullerene derivative [6,6]-phenyl-C70-butyric acid methyl ester (PC70BM) were exposed to simulated sunlight in air. Fourier-transform infrared spectra demonstrate the formation of carbonyl photo-oxidation products in the blend films, as well as in the pristine polymer and fullerene films. Solar cells prepared with photo-oxidized active layers show increasingly degraded electrical performance (lower short circuit current, open circuit voltage and fill factor) with increasing exposure time. The increased diode ideality factor indicates that trap-assisted recombination hinders device operation after exposure. The external quantum efficiency decreases drastically with increasing exposure time over the whole photon energy range, while the UV-vis absorption spectra of the blend films only show a mild photo-induced bleaching. This demonstrates that not only the photo-induced degradation of the solar cell performance is not predominantly caused by the loss in light absorption, but charge transport and collection are also hampered. This is explained by the fact that photo-oxidation of PC70BM causes bonds in its conjugated cage to break, as evidenced by the decreased ∏* intensity in C1s-NEXAFS spectra of PC70BM films. This degradation of unoccupied states of PC70BM will hinder the transport of photo-generated electrons to the electrode. Surface photovoltage spectroscopy gives direct evidence for gap states at the surface of a PC70BM film, formed after 2 hours of exposure and resulting in upward band bending at the PC70BM/air surface. These observations indicate that the photo-oxidation of PC70BM is likely to be the main cause of the performance degradation observed when the photoactive layer of a TQ1:PC70BM solar cell is intentionally exposed to light in air.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2019
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-75110 (URN)10.1039/C9CP04384E (DOI)000491079900005 ()
Funder
Swedish Energy Agency, 38327-1
Available from: 2019-10-07 Created: 2019-10-07 Last updated: 2019-11-14Bibliographically approved
Züfle, S., Hansson, R., Katz, E. A. & Moons, E. (2019). Initial photo-degradation of PCDTBT:PC 70 BM solar cells studied under various illumination conditions: Role of the hole transport layer. Solar Energy, 183(1), 234-239
Open this publication in new window or tab >>Initial photo-degradation of PCDTBT:PC 70 BM solar cells studied under various illumination conditions: Role of the hole transport layer
2019 (English)In: Solar Energy, ISSN 0038-092X, E-ISSN 1471-1257, Vol. 183, no 1, p. 234-239Article in journal (Refereed) Published
Abstract [en]

ncapsulated organic solar cells often show a burn-in behaviour under illumination. This burn-in manifests itself as a rapid performance loss followed by a much slower progression of the degradation. Here we investigate the burn-in for PCDTBT:PC 70 BM solar cells under a wide range of illumination intensities. We find that increasing the sunlight concentration from 1 Sun to up to 100 Suns does not change the degradation behaviour, i.e. the dependence of all principal photovoltaic parameters on the dose of solar exposure (in Sun hours). This suggests that the degradation mechanisms under solar concentration (≤100 Suns) are the same as those observed under 1 Sun. This result makes it possible to use concentrated sunlight for accelerated stability assessment of these devices. We also find that devices with PEDOT:PSS as hole transport material show a rapid drop in open-circuit voltage of around 100 mV during the first Sun hour of light exposure. By replacing PEDOT:PSS with MoO 3 this initial process can be prevented and only the much slower part of the photo-degradation takes place.

Place, publisher, year, edition, pages
Elsevier, 2019
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-47260 (URN)10.1016/j.solener.2019.03.020 (DOI)000467892000020 ()
Funder
Swedish Energy Agency, 38327-1Swedish Research Council, 2015-03778Göran Gustafsson Foundation for Research in Natural Sciences and Medicine, MP1307,STSM-MP1307-090216-070777
Note

Publicerad i Hanssons doktorsavhandling Materials and Device Engineering for Efficient and Stable Polymer Solar Cells som manuskript med titeln: "The role of the hole transport layer in the initial photo-degradation of PCDTBTPC70BM solar cells"

Available from: 2016-11-23 Created: 2016-11-23 Last updated: 2019-05-31Bibliographically approved
Chuan Chen, M., Omanakuttan, G., Hansson, R., Strömberg, A., Hallén, A., Rinio, M., . . . Sun, Y.-T. (2019). Low temperature activation of B implantation of Si subcell fabrication in III-V/Si tandem solar cells. In: Proceedings of the 36th EU PVSEC 2019: . Paper presented at European Photovoltaic Solar Energy Conference, Marseille (2019) (pp. 764-768). WIP
Open this publication in new window or tab >>Low temperature activation of B implantation of Si subcell fabrication in III-V/Si tandem solar cells
Show others...
2019 (English)In: Proceedings of the 36th EU PVSEC 2019, WIP, 2019, p. 764-768Conference paper, Published paper (Other academic)
Abstract [en]

In this work, we investigated the Si pre-amorphization implantation (PAI) assisted low temperatureannealing process to activate boron implantation in n-Si in a hydride vapor phase epitaxy (HVPE) reactor, which canbe used for the Si subcell fabrication in the III-V/Si tandem solar cells enabled by the corrugated epitaxial lateralovergrowth (CELOG). A uniform boron activation in Si and a low emitter sheet resistance of 77 /sq was obtained atannealing temperatures of 600-700°C. High-resolution x-ray diffraction was used to study the recrystallization ofamorphous silicon and the incorporation of boron dopants in Si. Hall measurements revealed p-type carrierconcentrations in the order of 1020 cm-3. The n-Si wafers with B implantation activated at 700°C by HVPE wereprocessed to solar cells and characterized by the standard light-current-voltage measurement under AM1.5 spectrumand external quantum efficiency measurements. The developed B implantation and low temperature activationprocesses are applied to the InP/Si seed template preparation for CELOG, on which CELOG GaInP over a Si subcellwith a direct heterojunction was demonstrated.

Place, publisher, year, edition, pages
WIP, 2019
Keywords
Multijunction Solar Cell, III-V semiconductors, Annealing, Amorphous Silicon
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-74774 (URN)10.4229/EUPVSEC20192019-3BV.2.55 (DOI)3-936338-60-4 (ISBN)
Conference
European Photovoltaic Solar Energy Conference, Marseille (2019)
Funder
Swedish Energy Agency, 40176-1
Available from: 2019-09-16 Created: 2019-09-16 Last updated: 2019-11-21Bibliographically approved
Ciammaruchi, L., Hansson, R., Moons, E. & Galagan, Y. (2018). Stability of organic solar cells with PCDTBT donor polymer: An interlaboratory study. Journal of Materials Research, 33(13), 1909-1924
Open this publication in new window or tab >>Stability of organic solar cells with PCDTBT donor polymer: An interlaboratory study
2018 (English)In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 33, no 13, p. 1909-1924Article in journal (Refereed) Published
Abstract [en]

This work is part of the interlaboratory collaboration to study the stability of organic solar cells containing PCDTBT polymer as a donor material. The varieties of the OPV devices with different device architectures, electrode materials, encapsulation, and device dimensions were prepared by seven research laboratories. Sets of identical devices were aged according to four different protocols: shelf lifetime, laboratory weathering under simulated illumination at ambient temperature, laboratory weathering under simulated illumination, and elevated temperature (65 degrees C) and daylight outdoor weathering under sunlight. The results generated in this study allow us to outline several general conclusions related to PCDTBT-based bulk heterojunction (BHJ) solar cells. The results herein reported can be considered as practical guidance for the realization of stabilization approaches in BHJ solar cells containing PCDTBT.

Place, publisher, year, edition, pages
New York: Cambridge University Press, 2018
Keywords
energetic material, nanoscale, organic
National Category
Physical Sciences Materials Chemistry
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-68746 (URN)10.1557/jmr.2018.163 (DOI)000438739300009 ()
Available from: 2018-08-16 Created: 2018-08-16 Last updated: 2018-10-18Bibliographically approved
Farinhas, J., Oliveira, R., Hansson, R., Ericsson, L., Moons, E., Morgado, J. & Charas, A. (2017). Efficient ternary organic solar cells based on immiscible blends. Organic electronics, 41, 130-136
Open this publication in new window or tab >>Efficient ternary organic solar cells based on immiscible blends
Show others...
2017 (English)In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 41, p. 130-136Article in journal (Refereed) Published
Abstract [en]

Organic photovoltaic cells based on ternary blends of materials with complementary properties represent an approach to improve the photon-absorption and/or charge transport within the devices. However, the more complex nature of the ternary system, i.e. in diversity of materials' properties and morphological features, complicates the understanding of the processes behind such optimizations. Here, organic photovoltaic cells with wider absorption spectrum composed of two electron-donor polymers, F8T2, poly(9,9-dioctylfluorene-alt-bithiophene), and PTB7, poly([4,8-bis[(2'-ethylhexyl) oxy] benzo[1,2-b: 4,5-b'] dithiophene-2,6-diyl][3-fluoro-2-[(2'-ethylhexyl) carbonyl] thieno[3,4-b] thiophenediyl]), mixed with [6,6]-phenyl-C-61-butyric acid methyl ester (PC61BM) are investigated. We demonstrate an improvement of 25% in power conversion efficiency in comparison with the most efficient binary blend control devices. The active layers of these ternary cells exhibit gross phase separation, as determined by Atomic Force Microscopy (AFM) and Synchrotron-based Scanning Transmission X-ray Microscopy (STXM).

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Polymer solar cells, Photovoltaics, Ternary blend, Morphology, High efficiency
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-62620 (URN)10.1016/j.orgel.2016.12.009 (DOI)000390586300017 ()
Available from: 2017-08-10 Created: 2017-08-10 Last updated: 2019-10-28Bibliographically approved
Chavhan, S. D., Hansson, R., Ericsson, L., Beyer, P., Hofmann, A., Brütting, W., . . . Moons, E. (2017). Low temperature processed NiOx hole transport layers for efficient polymer solar cells. Organic electronics, 44, 59-66
Open this publication in new window or tab >>Low temperature processed NiOx hole transport layers for efficient polymer solar cells
Show others...
2017 (English)In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 44, p. 59-66Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
OPV Nickel oxide Hole injection layer UV-ozone Kelvin probe XPS
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-47258 (URN)10.1016/j.orgel.2017.01.040 (DOI)000397441800009 ()
Funder
Swedish Energy Agency, 38327-2Swedish Research Council, 2015-03778Göran Gustafsson Foundation for Research in Natural Sciences and Medicine
Available from: 2016-11-23 Created: 2016-11-23 Last updated: 2019-10-28Bibliographically approved
Hansson, R. (2017). Materials and Device Engineering for Efficient and Stable Polymer Solar Cells. (Doctoral dissertation). Karlstad: Karlstads universitet
Open this publication in new window or tab >>Materials and Device Engineering for Efficient and Stable Polymer Solar Cells
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Polymer solar cells form a promising technology for converting sunlight into electricity, and have reached record efficiencies over 10% and lifetimes of several years. The performance of polymer solar cells depends strongly on the distribution of electron donor and acceptor materials in the active layer. To achieve longer lifetimes, degradation processes in the materials have to be understood. In this thesis, a set of complementary spectroscopy and microscopy techniques, among which soft X-ray techniques have been used to determine the morphology of polymer:fullerene based active layers. We have found that the morphology of TQ1:PC70BM films is strongly influenced by the processing solvent and the use of solvent additives. We have also found, by using soft X-ray techniques, that not only the light-absorbing polymer TQ1, but also the fullerene is susceptible to photo-degradation in air. Moreover, the fullerene degradation is accelerated in the presence of the polymer. Additionally, this thesis addresses the role of the interfacial layers for device performance and stability. The commonly used hole transport material PEDOT:PSS has the advantage of being solution processable at room temperature, but this layer is also known to contribute to the device degradation. We have found that low-temperature processed NiOx is a promising alternative to PEDOT:PSS, leading to improved device performance. Even for encapsulated polymer solar cells, some photo-induced degradation of the electrical performance is observed and is found to depend on the nature of the hole transport material. We found a better initial stability for solar cells with MoO3 hole transport layers than with PEDOT:PSS. In the pursuit of understanding the initial decrease in electrical performance of PEDOT:PSS-based devices, simulations were performed, from which a number of degradation sources could be excluded.

Abstract [en]

With the increasing global demand for energy, solar cells provide a clean method for converting the abundant sunlight to electricity. Polymer solar cells can be made from a large variety of light-harvesting and electrically conducting molecules and are inexpensive to produce. They have additional advantages, like their mechanical flexibility and low weight, which opens opportunities for novel applications. In order for polymer solar cells to be more competitive, however, both the power conversion efficiencies and lifetimes need to further improve. One way to achieve this is to optimize the morphology of the active layer. The active layer of a polymer solar cell consists of electron donating and electron accepting molecules whose distribution in the bulk of the film is a major factor that determines the solar cell performance.

This thesis presents the use of complementary spectroscopy and microscopy methods to probe the local composition in the active layer of polymer solar cells. The stability of the active layer is studied and the interplay between the photo-degradation of the donor and acceptor molecules is investigated. Additionally, this thesis addresses how the interfacial layers between the active layer and the electrodes can influence device performance and stability.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2017. p. 75
Series
Karlstad University Studies, ISSN 1403-8099 ; 2017:2
Keywords
polymer solar cell, photovoltaics, morphology, photo-degradation, conjugated polymer, fullerene, synchroton-based techniques, hole transport layers
National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-47257 (URN)978-91-7063-736-0 (ISBN)978-91-7063-739-1 (ISBN)
Public defence
2017-02-03, 21A342, Karlstads universitet, Karlstad, 13:15 (English)
Opponent
Supervisors
Note

I publikationen felaktigt ISBN 978-91-7063-739-1

Artikel 5 publicerad i avhandlingen som manuskript med titeln "The role of the hole transport layer in the initial photo-degradation of PCDTBT: PC70BM solar cells"

Available from: 2017-01-13 Created: 2016-11-23 Last updated: 2019-10-28Bibliographically approved
Hansson, R., Ericsson, L., Holmes, N. P., Blazinic, V., Dastoor, P. & Moons, E. (2017). Opportunities and challenges in probing local composition of organic material blends for photovoltaics. Journal of Materials Research, 32(10), 1982-1992
Open this publication in new window or tab >>Opportunities and challenges in probing local composition of organic material blends for photovoltaics
Show others...
2017 (English)In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 32, no 10, p. 1982-1992Article in journal (Refereed) Published
Place, publisher, year, edition, pages
Materials Research Society, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kau:diva-47259 (URN)10.1557/jmr.2017.7 (DOI)000402284600014 ()
Funder
Swedish Energy Agency, 38327-1Swedish Research Council, 2015-03778Göran Gustafsson Foundation for Research in Natural Sciences and Medicine
Available from: 2016-11-23 Created: 2016-11-23 Last updated: 2019-11-21Bibliographically approved
Opitz, A., Wilke, A., Amsalem, P., Oehzelt, M., Blum, R.-P., Rabe, J. P., . . . Koch, N. (2016). Organic heterojunctions: Contact-induced molecular reorientation, interface states, and charge redistribution. Scientific Reports, 6, Article ID 21291.
Open this publication in new window or tab >>Organic heterojunctions: Contact-induced molecular reorientation, interface states, and charge redistribution
Show others...
2016 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 6, article id 21291Article in journal (Refereed) Published
Abstract [en]

We reveal the rather complex interplay of contact-induced re-orientation and interfacial electronic structure-in the presence of Fermi-level pinning-at prototypical molecular heterojunctions comprising copper phthalocyanine (H16CuPc) and its perfluorinated analogue (F16CuPc), by employing ultraviolet photoelectron and X-ray absorption spectroscopy. For both layer sequences, we find that Fermi-level (E-F) pinning of the first layer on the conductive polymer substrate modifies the work function encountered by the second layer such that it also becomes E-F-pinned, however, at the interface towards the first molecular layer. This results in a charge transfer accompanied by a sheet charge density at the organic/organic interface. While molecules in the bulk of the films exhibit upright orientation, contact formation at the heterojunction results in an interfacial bilayer with lying and co-facial orientation. This interfacial layer is not EF-pinned, but provides for an additional density of states at the interface that is not present in the bulk. With reliable knowledge of the organic heterojunction's electronic structure we can explain the poor performance of these in photovoltaic cells as well as their valuable function as charge generation layer in electronic devices.

National Category
Physical Sciences
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-41201 (URN)10.1038/srep21291 (DOI)000370370200001 ()26887445 (PubMedID)
Available from: 2016-04-01 Created: 2016-04-01 Last updated: 2018-06-20Bibliographically approved
Hansson, R., Lindqvist, C., Ericsson, L., Opitz, A., Wang, E. & Moons, E. (2016). Photodegradation in air of the active layer components in a thiophene-quinoxaline copolymer:fullerene solar cell. Physical Chemistry, Chemical Physics - PCCP, 18(16), 11132-11138
Open this publication in new window or tab >>Photodegradation in air of the active layer components in a thiophene-quinoxaline copolymer:fullerene solar cell
Show others...
2016 (English)In: Physical Chemistry, Chemical Physics - PCCP, ISSN 1463-9076, E-ISSN 1463-9084, Vol. 18, no 16, p. 11132-11138Article in journal (Refereed) Published
Abstract [en]

We have studied the photo-degradation in air of a blend of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and poly[2,3-bis-(3-octyloxyphenyl)quinoxaline-5,8-diyl-alt-thiophene-2,5-diyl] (TQ1), and how the photo-degradation affects the solar cell performance. Using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, changes to the electronic structure of TQ1 and PCBM caused by illumination in ambient air are investigated and compared between the pristine materials and the blend. The NEXAFS spectra show that the unoccupied molecular orbitals of TQ1 are not significantly changed by the exposure of pristine TQ1 to light in air, whereas those of PCBM are severely affected as a result of photo-induced degradation of PCBM. Furthermore, the photo-degradation of PCBM is accelerated by blending it with TQ1. While the NEXAFS spectrum of TQ1 remains unchanged upon illumination in air, its valence band spectrum shows that the occupied molecular orbitals are weakly affected. Yet, UV-Vis absorption spectra demonstrate photo-bleaching of TQ1, which is attenuated in the presence of PCBM in blend films. Illumination of the active layer of TQ1: PCBM solar cells prior to cathode deposition causes severe losses in electrical performance.

Keywords
polymer solar cells, photodegradation, fullerene, near-edge X-ray absorption fine structure
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:kau:diva-37835 (URN)10.1039/c5cp07752d (DOI)000374786300053 ()
Available from: 2015-09-04 Created: 2015-09-03 Last updated: 2018-06-20Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-4745-1074

Search in DiVA

Show all publications