| 1. |
- Arvizu, Miguel A, et al.
(författare)
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Electrochromism in sputter-deposited W-Ti oxide films : Durability enhancement due to Ti
- 2014
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 125, s. 184-189
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Tidskriftsartikel (refereegranskat)abstract
- Thin films of W-Ti oxide were prepared by reactive DC magnetron sputtering and were characterized by Rutherford bathcattering spectrometry, X-ray diffraction, scanning electron microscopy and atomic force microscopy. The electrochromic properties were studied by cyclic voltammetry in an electrolyte of lithium perchlorate in propylene carbonate and by optical transmittance measurements. The addition of Ti significantly promoted the amorphous nature of the films and stabilized their electrochemical cycling performance and dynamic range for electrochromism. (C) 2014 Elsevier B.V. All rights reserved.
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| 2. |
- Baier, Robert, et al.
(författare)
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Electronic properties of grain boundaries in Cu(In,Ga)Se-2 thin films with various Ga-contents
- 2012
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248. ; 103, s. 86-92
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Tidskriftsartikel (refereegranskat)abstract
- We present a study on the electronic properties of grain boundaries (GBs) in polycrystalline Cu(In,Ga)Se-2 (CIGSe) thin films by means of Kelvin probe force microscopy. As grown as well as KCN-treated films were investigated comparatively. No influence of the chemical treatment on the electronic properties of GBs was found. GBs generally exhibited large variations in their electronic properties. By means of a novel method of data analysis both potential barriers for holes and electrons were found at GBs, in a range from -118 mV to +114 mV, as well as GBs without potential barrier. No dependence of the electronic GB-properties on the Ga-content was detected. Consequently, we conclude that there is no correlation between the electronic properties of GBs and the obtained maximum efficiencies of CIGSe thin film solar cells as a function of the Ga-content. (C) 2012 Elsevier B.V. All rights reserved.
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| 3. |
- Barrios, David, et al.
(författare)
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Toward a quantitative model for suspended particle devices : Optical scattering and absorption coefficients
- 2013
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 111, s. 115-122
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Tidskriftsartikel (refereegranskat)abstract
- Suspended particle devices (SPDs) allow rapid voltage-controlled modulation of their optical transmittance and are of interest for solar-energy-related and other applications. We investigated the spectral total and diffuse transmittance of an SPD, including its angular dependence. The optical modulation was large for visible light but almost nil in the infrared, and the devices had noticeable haze. A theoretical two-flux model was formulated and provided a quantitative description of the absorption and scattering coefficients and thereby of the detailed optical performance. This analysis gives a benchmark for assessing improvements of the SPD technology as well as for comparing it with alternative technologies for optical modulation.
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| 4. |
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| 5. |
- Bayrak Pehlivan, Ilknur, et al.
(författare)
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[PEI-SiO2]:[LiTFSI] nanocomposite polymer electrolytes : Ion conduction and optical properties
- 2012
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 98, s. 465-471
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Tidskriftsartikel (refereegranskat)abstract
- Ion conductivity and optical properties were investigated for polymer electrolytes based on poly (ethyleneimine) and lithium bis(trifluoromethylsulfonyl)imide and also containing up to 9 wt.% of 7-nm-diameter SiO2 nanoparticles. The [N]:[Li] molar ratio was kept constant at 50:1. Impedance measurements were performed in the frequency range 10(-2)-10(7) Hz and between the temperatures 20 and 70 degrees C with an applied ac voltage of 1 V. Spectrophotometric data of total and diffuse transmittance were taken between the wavelengths 300 and 2500 nm. The bulk impedance was fitted to a conductive Havriliak-Negami circuit model. The ion conductivity increased monotonically for increasing SiO2 contents: specifically its room temperature value went from 8.5 x 10(-7) S/cm without nanoparticles to 3.8 x 10(-5) S/cm for 8 wt.% of SiO2 while the diffuse transmittance remained at similar to 1% so that optical clarity prevailed.
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| 6. |
- Bergqvist, Jonas, et al.
(författare)
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In situ reflectance imaging of organic thin film formation from solution deposition
- 2013
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier. - 0927-0248 .- 1879-3398. ; 114, s. 89-98
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Tidskriftsartikel (refereegranskat)abstract
- In this work we present reflectance imaging as a suitable method for in situ monitoring of the drying process of film formation for organic photovoltaics (OPV) over large areas, as well as for lab-scale spin-coating. The drying wet film is illuminated with a narrow bandwidth LED with the specularly reflected light recorded by a video camera as the film dries and forms the active layer of the OPV cell. The interference fringes generated by the thinning wet film can be used to measure the rate of solvent evaporation and the drying time. Subsequent mapping elucidates variations in drying conditions over the substrate, which lead to variations in morphology formation. The technique is suitable for tracking thickness variations of the dry film, with a sensitivity of 10 nm, by comparing the intensity of the reflected light from the dry film to simulated interference conditions calculated for each thickness. The drying process is furthermore accurately simulated by an optical model considering the changes in refractive index as the amount of solvent decreases with respect to the solid content. This non-invasive in situ method represents an important monitoring tool for future large scale OPV manufacturing where high performing morphologies with uniform thickness have to be formed over very large areas.
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| 7. |
- Cai, Tianqi, et al.
(författare)
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Low bandgap polymers synthesized by FeCl(3) oxidative polymerization
- 2010
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248. ; 94:7, s. 1275-1281
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Tidskriftsartikel (refereegranskat)abstract
- Four low bandgap polymers, combining an alkyl thiophene donor with benzo[c][1,2,5]thiadiazole, 2,3-diphenylquinoxaline, 2,3-diphenylthieno[3,4-b]pyrazine and 6,7-diphenyl-[1,2,5]thiadiazolo[3,4-g] quinoxaline acceptors in a donor-acceptor-donor architecture, were synthesized via FeCl3 oxidative polymerization. The molecular weights of the polymers were improved by introducing o-dichlor-obenzene (ODCB) as the reaction solvent instead of the commonly used solvent, chloroform. The photophysical, electrochemical and photovoltaic properties of the resulting polymers were investigated and compared. The optical bandgaps of the polymers vary between 1.0 and 1.9 eV, which is promising for solar cells. The devices spin-coated from an ODCB solution of P1DB:[70]PCBM showed a power conversion efficiency of 1.08% with an open-circuit voltage of 0.91 V and a short-circuit current density of 3.36 mA cm(-2) under irradiation from an AM1.5G solar simulator (100 mW cm(-2)). (C) 2010 Elsevier B.V. All rights reserved.
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| 8. |
- Chen, Zhi-Hui, et al.
(författare)
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Comb-shaped photonic crystal structure for efficient broadband light diffraction and funnelling in solar cells
- 2012
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 99, s. 316-320
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Tidskriftsartikel (refereegranskat)abstract
- We present a comb-shaped photonic-crystal (PhC) rods-lattice structure of broadband light diffraction and funnelling for solar cell applications. It is shown that the photonic band of this PhC structure is very dispersive over a broad bandwidth so that light will be efficiently diffracted in the wavelength region of solar radiation. The PhC structure also creates resonance modes leading to further diffraction and funnelling of light so that the light propagates in many pathways in the whole PhC lattice region, which will greatly facilitate light-matter interaction when light-absorbing elements are embedded in the PhC structure. The proposed structure is also valid for photodetection applications.
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| 9. |
- El Daif, O., et al.
(författare)
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Front side plasmonic effect on thin silicon epitaxial solar cells
- 2012
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Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248. ; 104, s. 58-63
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Tidskriftsartikel (refereegranskat)abstract
- We study the effect of metal nanoparticles, showing localised plasmonic resonances, on the spectrally resolved efficiency of thin film crystalline silicon solar cells. We investigate model structures: silver (Ag) nanodiscs on the surface of epitaxial cells grown on highly doped silicon substrates, with a controlled micron-scale thickness. The cells have no back reflector in order to exclusively study the effect of the front surface on their optical properties. The nanodiscs were deposited through hole-mask colloidal lithography, which is a low-cost, bottom-up and extremely versatile technique. As opposed to many other works, we use as benchmarks both bare silicon cells and cells with a dielectric antireflection coating. We optically observe a resonance showing an absorption increase, found to be controllable by the discs parameters. We also see an increase in short-circuit current with respect to bare cells, but we see a decrease in efficiency with respect to cells with a dielectric antireflection coating, due to losses at short wavelengths. As the material properties are not notably affected by the particles deposition, we show that the main loss mechanisms are an important parasitic absorption in the nanoparticles and destructive interferences.
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| 10. |
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