Showing papers by "Jürgen H. Werner published in 2004"
TL;DR: In this paper, the radiative recombination limit of photovoltaic power conversion under one sun terrestrial illumination was calculated for solar cells with lateral fluctuations of the band-gap energy, and a simple analytical model quantified the fluctuations by the standard deviation σEg from the mean band gap.
Abstract: The radiative recombination limit of photovoltaic power conversion under one sun terrestrial illumination is calculated for solar cells with lateral fluctuations of the band-gap energy. A simple analytical model quantifies the fluctuations by the standard deviation σEg from the mean band gap. The calculated maximum efficiency decreases by 1.7% (absolute) for σEg=50 meV and by 6.1% for σEg=100 meV with respect to a uniform band gap.
195 citations
TL;DR: In this paper, spatial variations of the electronic properties of solar cells are simulated with the help of a multi-diode model, and an optimum local series resistance for maximum power conversion efficiency is found.
Abstract: Spatial variations of the electronic properties of solar cells are simulated with the help of a multi-diode model. Increasing the local series resistance limits the degradation of the overall performance by reducing losses of the open circuit voltage originating from cell areas with minor electronic quality. At the same time, the fill factor of the device decreases such that an optimum local series resistance for maximum power conversion efficiency is found. The value of the optimum series resistance depends on the degree of electronic inhomogeneity. Thus, optimization rules for spatially uniform solar cells are different from those for nonuniform cells.
88 citations
TL;DR: In this article, annealing experiments with thin Cu(In, Ga)Se 2 films were performed to analyze grain growth on the basis of a kinetic growth model, and the results showed that the average grain size increased by a factor of 2.4.
48 citations
TL;DR: In this article, the microstructure of Cu(In,Ga)Se2 thin films with different preferred grain orientations (textures) was investigated with a cathodoluminescence spectrometer attached to a transmission electron microscope.
Abstract: We investigate the microstructure of Cu(In,Ga)Se2 thin films with different preferred grain orientations (textures). The films are grown by coevaporation from elemental sources. We analyse the electro-optical properties of the films with a cathodoluminescence spectrometer attached to a transmission electron microscope. {112} textured films show sharp contrasts at the grain boundaries, whereas grain boundaries in {220/204} textured films give only very weak contrasts indicating a preferential population of electronically rather inactive grain boundaries.
34 citations
TL;DR: In this paper, the authors investigated the suitability of thin-film solar cells for application under low irradiance conditions with irradiance E 10 kΩ cm2 of the solar cells and found that the shunt resistance of these solar cells originates from highly localised shunt regions in the absorber material.
26 citations
Patent•
26 Jul 2004
TL;DR: Verfahren>>\zur Erzeugung eines dotierten Bereichs in einem Festkorper, bei¯¯¯¯welchem as mentioned in this paper, einSourceFileMedium, welches einen Dotierstoff enthalt, mit einer Oberflache des¯¯¯¯Festkorpers Kontakt gebracht, was verkleinerte Abbildung des Linienfokus.
Abstract: Verfahren
zur Erzeugung eines dotierten Bereichs in einem Festkorper, bei
welchem – ein
Medium, welches einen Dotierstoff enthalt, mit einer Oberflache des
Festkorpers
in Kontakt gebracht wird, – durch
Bestrahlung mit Laserimpulsen ein Bereich des Festkorpers unterhalb
der mit dem Medium kontaktierten Oberflache kurzzeitig aufgeschmolzen
wird, so dass der Dotierstoff in den aufgeschmolzenen Bereich eindiffundiert und
wahrend
des Abkuhlens
der aufgeschmolzene Bereich rekristallisiert, und – der Laserstrahl
in einem Linienfokus auf den Festkorper fokussiert wird, dadurch
gekennzeichnet, dass – mittels
einer Zylinderlinse ein Linienfokus erzeugt wird und mittels eines
Objektivs eine verkleinerte Abbildung des Linienfokus auf der Oberflache des
Festkorpers
derart erzeugt wird, dass die Breite des Linienfokus kleiner als
10 μm betragt, und – die Lange des
Linienfokus in einem Bereich oberhalb von 100 μm liegt
4 citations
Patent•
26 Jul 2004
TL;DR: In this article, a method for producing a doped region in a solid body is described, where a medium containing a dopant is brought into contact with a surface of the solid body, and an area of the surface of a solid is briefly melted below the contacted with the medium surface by irradiation with laser pulses so that the dopant in the melted area is diffused and recrystallized during cooling of the melted region and the laser beam is focused in a line focus on the solids.
Abstract: A method for producing a doped region in a solid body, wherein - a medium containing a dopant is brought into contact with a surface of the solid body, - an area of the solid is briefly melted below the contacted with the medium surface by irradiation with laser pulses so that the dopant in the melted area is diffused and recrystallized during cooling of the melted region and - the laser beam is focused in a line focus on the solids, characterized, in that - by means of a cylindrical lens, a line focus is generated and a reduced image of the line focus is generated on the surface of the solid body in such a manner by means of a lens, the width of the line focus is less than 10 micrometres, and - is the length of the line focus in a range above 100 microns
1 citations