| 1. |
- Johansson, Erik M .J., et al.
(författare)
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Interfacial properties of photovoltaic TiO2/dye/PEDOT-PSS heterojunctions
- 2005
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Ingår i: Synthetic metals. - : Elsevier BV. - 0379-6779 .- 1879-3290. ; 149:03-feb, s. 157-167
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Tidskriftsartikel (refereegranskat)abstract
- Systems comprising a dense TiO2 film electrode, a ruthenium polypyridine dye and a PEDOT-PSS (poly(3,4-ethylenedioxythiophene)-poly(4-styrenesulphonate)) film were prepared. The heterojunctions were shown to have photovoltaic properties, with the dye absorbing the light, the TiO2 acting as an electron conducting material and PEDOT-PSS acting as a hole transport material. A series of dyes was used to investigate their influence on the photocurrent and the photovoltage characteristics of the heterojunction. These results were compared to a photoelectrochemical system in which the PEDOT-PSS was replaced by a liquid electrolyte containing triiodide/iodide redox-couple. Photoelectron spectroscopy (PES) was used to monitor the interfacial properties of the heterojunction and the investigation points out effects of importance when assembling the materials together to a functional unit. Specifically, it was concluded that the interaction with the dye clearly affects the structure of PEDOT-PSS, both with respect to the surface composition of PSS relative to PEDOT and with respect to the chemical state of the sulphur in the polymers. Moreover, a comparison of the Ru3d and the valence band spectra of the two different interfaces (dye/TiO2 and dye/PEDOT-PSS) indicates that the energy level structure of the dyes compared to the substrate is different for the two surfaces. Thus, in the combined energy level picture under dark conditions, the energy levels in TiO2 relative to the energy levels in PEDOT-PSS depend on the dye.
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| 2. |
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| 3. |
- Hamrin, Kjell, et al.
(författare)
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Ionization energies in methane and ethane measured by means of ESCA
- 1968
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 1:13, s. 613-615
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Tidskriftsartikel (refereegranskat)abstract
- Ionization energies for the molecular orbitals in methane and ethane are obtained by means of the ESCA technique. In methane the 2a(1) electrons are found at a binding energy of 23.1 eV: in ethane the 2a(1) level is split up in two levels due to the interaction between the carbon atoms.
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| 4. |
- Hamrin, Kjell, et al.
(författare)
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Structure studies of sulphur compounds by ESCA
- 1968
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Ingår i: Chemical Physics Letters. - 0009-2614 .- 1873-4448. ; 1:11, s. 557-559
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Tidskriftsartikel (refereegranskat)abstract
- Results, obtained by means of the ESCA-technique (Electron Spectroscopy for Chemical Analysis), are reported on the correlation between the binding energy of the inner electrons of sulphur and the chemical state and environment, with particular emphasis on the sulphur-oxygen bond. A charge-binding energy correlation is established which can be used for the estimation of charge on sulphur in compounds with uncertain structure or composition.
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| 5. |
- Henningsson, Anders, 1969-
(författare)
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Ion Insertion into Electrode Materials Studied with X-Ray and Electron Spectroscopic Methods
- 2002
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Ion insertion into electrode materials can be used to store energy in battery applications. In this thesis, photoelectron spectroscopic and x-ray absorption spectroscopic methods have been used to study the change of the electronic structure of host materials during electrochemical ion insertion. Specifically, the properties of ion insertion into nanoporous TiO2 were studied. It is demonstrated that the insertion of Li ions results in a reduction of the Ti4+ sites in TiO2 to Ti3+ sites close to the inserted Li ion. The intensity of the Ti3+ is directly correlated to the number of inserted electrons. It is also shown that the two phases resulting from moderate insertion can be detected by studying the electronic structure of inserted Li ions and the behavior observed can be correlated with electrochemical measurements. Insertion of ions into tungsten oxides is a potential candidate for smart window and display applications. Ion insertion into these materials was, also studied with electron spectroscopic methods. The insertion of H+ reduces W6+ to W5+ and further insertion results in a reduction to W4+. Cyclic voltammerty shows two reduction peaks where the first peak implies reduction of W6+ to W5+ and the second peak can be associated with further reduction to W4+.During the first charge/discharge cycles of a battery based on graphite anodes a solid electrolyte interface layer is formed on the electrode surface. This layer consumes some of the charge carrying Li ions, hence decreases the capacity of the battery. A careful characterization of this layer has been performed to aid in the further development of this type of battery.
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| 6. |
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| 7. |
- Sinno, Hiam, 1983-, et al.
(författare)
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Amphiphilic semiconducting copolymer as compatibility layer for printing polyelectrolyte-gated OFETs
- 2013
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Ingår i: Organic electronics. - : Elsevier. - 1566-1199 .- 1878-5530. ; 14:3, s. 790-796
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Tidskriftsartikel (refereegranskat)abstract
- We report a method for inkjet-printing an organic semiconductor layer on top of the electrolyte insulator layer in polyelectrolyte-gated OFETs by using a surface modification treatment to overcome the underlying wettability problem at this interface. The method includes depositing an amphiphilic diblock copolymer (P3HT-b-PDMAEMA). This material is designed to have one set of blocks that mimics the hydrophobic properties of the semiconductor (poly(3-hexylthiophene) or P3HT), while the other set of blocks include polar components that improve adhesion to the polyelectrolyte insulator. Contact angle measurements, atomic force microscopy, and X-ray photoelectron spectroscopy confirm formation of the desired surface modification film. Successful inkjet printing of a smooth semiconductor layer allows us to manufacture complete transistor structures that exhibit low-voltage operation in the range of 1 V.
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| 8. |
- Zhang, Tiankai, et al.
(författare)
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Ion-modulated radical doping of spiro-OMeTAD for more efficient and stable perovskite solar cells
- 2022
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Ingår i: Science. - : AMER ASSOC ADVANCEMENT SCIENCE. - 0036-8075 .- 1095-9203. ; 377:6605, s. 495-501
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Tidskriftsartikel (refereegranskat)abstract
- Record power conversion efficiencies (PCEs) of perovskite solar cells (PSCs) have been obtained with the organic hole transporter 2,2,7,7-tetrakis(N,N-di-p-methoxyphenyl-amine)9,9-spirobifluorene (spiro-OMeTAD). Conventional doping of spiro-OMeTAD with hygroscopic lithium salts and volatile 4-tert-butylpyridine is a time-consuming process and also leads to poor device stability. We developed a new doping strategy for spiro-OMeTAD that avoids post-oxidation by using stable organic radicals as the dopant and ionic salts as the doping modulator (referred to as ion-modulated radical doping). We achieved PCEs of >25% and much-improved device stability under harsh conditions. The radicals provide hole polarons that instantly increase the conductivity and work function (WF), and ionic salts further modulate the WF by affecting the energetics of the hole polarons. This organic semiconductor doping strategy, which decouples conductivity and WF tunability, could inspire further optimization in other optoelectronic devices.
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