6 results on '"Orgis, Thomas"'
Search Results
2. Influence of band gradients on Cu(In,Ga)Se2 solar cell diode factors.
- Author
-
Orgis, Thomas, Maiberg, Matthias, and Scheer, Roland
- Subjects
- *
SOLAR cells , *BAND gaps , *DIODES , *SPACE charge , *CONDUCTION bands - Abstract
The influence of band gap gradients on the charge collection and diode quality factor of solar cells is investigated by device simulation. A back surface band gap gradient manifested as a gradient of the conduction band is found to lead to an increased diode quality factor. Thus, the positive influence of the gradient on the fill factor is partially counterbalanced by the diode quality factor increase. The reason for the latter is the enhanced contribution of space charge region recombination. If the cell is equipped with a double gradient at front and back surfaces, the detrimental diode factor increase can be suppressed. The relevance of the findings is investigated using different carrier lifetimes and doping levels. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
3. Odd-even effects and the influence of length and specific positioning of alkoxy side chains on the optical properties of PPE-PPV polymers
- Author
-
Egbe, D. A. M., Ulbricht, C., Orgis, Thomas, Carbonnier, B., Kietzke, Thomas, Peip, M., Metzner, M., Gericke, M., Birckner, Eckhard, Pakula, T., Neher, Dieter (Prof. Dr.), and Grumm, U. W.
- Subjects
Institut für Physik und Astronomie - Abstract
This contribution reports the combined influences of odd-even effects and the specific positioning of alkoxy side chains OR1 = (OCn+H-10(2(n+10)+1)) and OR2 = (OCnH2n+1) (with n = 6, 7, 8, 9) on the phenylene-ethynylene and phenylene- vinylene segments, respectively, on the optical properties of hybrid polymers P(n+10)/n of general repeating unit: -Ph-C equivalent to C-Ph-C equivalent to C-Ph-CH=CH-Ph-CH=CH-. For the polymeric materials, visual color impression varies alternatively between orange red (P16/6 and P18/8) and yellow (P17/7 and P19/9) according to the odd and even features of the alkoxy side chains, where odd or even relates to the total number of sp(3)-hybridized atoms within the side chains. This side chain related effect is ascribed to both absorptive and emissive behaviors of the polymers on the basis of photophysical investigations in the bulk. Almost identical thin film absorption spectra were obtained for all four materials; however, the photoluminescence of the odd polymers, P16/6 (lambda(f) = 556 nm) and P18/ 8 (lambda(f) = 614 nm), was red-shifted relative to that of their even counterparts (lambda(f) = 535 nm). Further, the P18/8 maximum at 614 nm can be readily assigned to excimer emission, as evidenced by the largest Stokes shift (5600 cm(- 1)), largest fwhmf-value (3700 cm(-1))(,) and the lowest Phi(f)-value of 24%. The strong pi-pi interchain interaction in P18/8, due to loose alkoxy side chains packing, does not only favor fluorescence quenching but also enable an effective inter- as well as intra-molecular recombination of the generated positive and negative polarons in electrolurninescence, which explains the good EL properties of this polymer irrespective of the solvent used. A voltage-dependent blue shift of the EL spectra of up to 100 nm was observed for P18/8 devices prepared from aromatic solvents. This red to green EL shift as observed with increasing voltage is assigned to conformational changes of the polymer chains with increasing temperature
- Published
- 2005
4. Gallium gradients in Cu(In,Ga)Se2 thin-film solar cells.
- Author
-
Witte, Wolfram, Abou‐Ras, Daniel, Albe, Karsten, Bauer, Gottfried H., Bertram, Frank, Boit, Christian, Brüggemann, Rudolf, Christen, Jürgen, Dietrich, Jens, Eicke, Axel, Hariskos, Dimitrios, Maiberg, Matthias, Mainz, Roland, Meessen, Max, Müller, Mathias, Neumann, Oliver, Orgis, Thomas, Paetel, Stefan, Pohl, Johan, and Rodriguez‐Alvarez, Humberto
- Subjects
GALLIUM compounds ,SOLAR cells ,SOLAR batteries ,PHOTOVOLTAIC cells ,MASS spectrometry - Abstract
The gallium gradient in Cu(In,Ga)Se
2 (CIGS) layers, which forms during the two industrially relevant deposition routes, the sequential and co-evaporation processes, plays a key role in the device performance of CIGS thin-film modules. In this contribution, we present a comprehensive study on the formation, nature, and consequences of gallium gradients in CIGS solar cells. The formation of gallium gradients is analyzed in real time during a rapid selenization process by in situ X-ray measurements. In addition, the gallium grading of a CIGS layer grown with an in-line co-evaporation process is analyzed by means of depth profiling with mass spectrometry. This gallium gradient of a real solar cell served as input data for device simulations. Depth-dependent occurrence of lateral inhomogeneities on the µm scale in CIGS deposited by the co-evaporation process was investigated by highly spatially resolved luminescence measurements on etched CIGS samples, which revealed a dependence of the optical bandgap, the quasi-Fermi level splitting, transition levels, and the vertical gallium gradient. Transmission electron microscopy analyses of CIGS cross-sections point to a difference in gallium content in the near surface region of neighboring grains. Migration barriers for a copper-vacancy-mediated indium and gallium diffusion in CuInSe2 and CuGaSe2 were calculated using density functional theory. The migration barrier for the InCu antisite in CuGaSe2 is significantly lower compared with the GaCu antisite in CuInSe2 , which is in accordance with the experimentally observed Ga gradients in CIGS layers grown by co-evaporation and selenization processes. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]- Published
- 2015
- Full Text
- View/download PDF
5. The Spring-Time Boundary Layer in the Central Arctic Observed during PAMARCMiP 2009.
- Author
-
Lampert, Astrid, Maturilli, Marion, Ritter, Christoph, Hoffmann, Anne, Stock, Maria, Herber, Andreas, Birnbaum, Gerit, Neuber, Roland, Dethloff, Klaus, Orgis, Thomas, Stone, Robert, Brauner, Ralf, Kässbohrer, Johannes, Haas, Christian, Makshtas, Alexander, Sokolov, Vladimir, and Liu, Peter
- Subjects
ATMOSPHERIC boundary layer ,OPTICAL radar ,SEA ice ,ICE - Abstract
The Arctic atmospheric boundary layer (AABL) in the central Arctic was characterized by dropsonde, lidar, ice thickness and airborne in situ measurements during the international Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project (PAMARCMiP) in April 2009. We discuss AABL observations in the lowermost 500 m above (A) open water, (B) sea ice with many open/refrozen leads (C) sea ice with few leads, and (D) closed sea ice with a front modifying the AABL. Above water, the AABL had near-neutral stratification and contained a high water vapor concentration. Above sea ice, a low AABL top, low near-surface temperatures, strong surface-based temperature inversions and an increase of moisture with altitude were observed. AABL properties and particle concentrations were modified by a frontal system, allowing vertical mixing with the free atmosphere. Above areas with many leads, the potential temperature decreased with height in the lowest 50 m and was nearly constant above, up to an altitude of 100-200 m, indicating vertical mixing. The increase of the backscatter coefficient towards the surface was high. Above sea ice with few refrozen leads, the stably stratified boundary layer extended up to 200-300 m altitude. It was characterized by low specific humidity and a smaller increase of the backscatter coefficient towards the surface. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
6. Remote sensing and in-situ measurements of tropospheric aerosol, a PAMARCMiP case study
- Author
-
Hoffmann, Anne, Osterloh, Lukas, Stone, Robert, Lampert, Astrid, Ritter, Christoph, Stock, Maria, Tunved, Peter, Hennig, Tabea, Böckmann, Christine, Li, Shao-Meng, Eleftheriadis, Kostas, Maturilli, Marion, Orgis, Thomas, Herber, Andreas, Neuber, Roland, and Dethloff, Klaus
- Subjects
- *
TROPOSPHERIC aerosols , *REMOTE sensing , *PARTICLE size distribution , *SCATTERING (Physics) , *AIR pollution , *PHOTOMETRY , *BACKSCATTERING , *DATA analysis , *OPTICAL radar - Abstract
Abstract: In this work, a closure experiment for tropospheric aerosol is presented. Aerosol size distributions and single scattering albedo from remote sensing data are compared to those measured in-situ. An aerosol pollution event on 4 April 2009 was observed by ground based and airborne lidar and photometer in and around Ny-Ålesund, Spitsbergen, as well as by DMPS, nephelometer and particle soot absorption photometer at the nearby Zeppelin Mountain Research Station. The presented measurements were conducted in an area of 40 × 20 km around Ny-Ålesund as part of the 2009 Polar Airborne Measurements and Arctic Regional Climate Model Simulation Project (PAMARCMiP). Aerosol mainly in the accumulation mode was found in the lower troposphere, however, enhanced backscattering was observed up to the tropopause altitude. A comparison of meteorological data available at different locations reveals a stable multi-layer-structure of the lower troposphere. It is followed by the retrieval of optical and microphysical aerosol parameters. Extinction values have been derived using two different methods, and it was found that extinction (especially in the UV) derived from Raman lidar data significantly surpasses the extinction derived from photometer AOD profiles. Airborne lidar data shows volume depolarization values to be less than 2.5% between 500 m and 2.5 km altitude, hence, particles in this range can be assumed to be of spherical shape. In-situ particle number concentrations measured at the Zeppelin Mountain Research Station at 474 m altitude peak at about 0.18 μm diameter, which was also found for the microphysical inversion calculations performed at 850 m and 1500 m altitude. Number concentrations depend on the assumed extinction values, and slightly decrease with altitude as well as the effective particle diameter. A low imaginary part in the derived refractive index suggests weakly absorbing aerosols, which is confirmed by low black carbon concentrations, measured at the Zeppelin Mountain as well as on board the Polar 5 aircraft. [Copyright &y& Elsevier]
- Published
- 2012
- Full Text
- View/download PDF
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.