124 research outputs found
Unambiguous Determination of Local Orientations of Polycrystalline CuInSe2 Thin Films via Dictionary Based Indexing
Junction formation by Zn(O,S) sputtering yields CIGSe-based cells with efficiencies exceeding 18%
In an effort to reduce the complexity and associated production costs of
Cu(In,Ga)Se2 (CIGSe)-based solar cells, the commonly used sputtered undoped
ZnO layer has been modified to eliminate the requirement for a dedicated
buffer layer. After replacing the ZnO target with a mixed ZnO/ZnS target,
efficient solar cells could be prepared by sputtering directly onto the as-
grown CIGSe surface. This approach has now been tested with high-quality lab-
scale glass/Mo/CIGSe substrates. An efficiency of 18.3% has been independently
confirmed without any post-deposition annealing or light soaking
Reliable wet-chemical cleaning of natively oxidized high-efficiency Cu(In,Ga)Se2 thin-film solar cell absorbers
Currently, Cu-containing chalcopyrite-based solar cells provide the highest
conversion efficiencies among all thin-film photovoltaic (PV) technologies.
They have reached efficiency values above 20%, the same performance level as
multi-crystalline silicon-wafer technology that dominates the commercial PV
market. Chalcopyrite thin-film heterostructures consist of a layer stack with
a variety of interfaces between different materials. It is the
chalcopyrite/buffer region (forming the p-n junction), which is of crucial
importance and therefore frequently investigated using surface and interface
science tools, such as photoelectron spectroscopy and scanning probe
microscopy. To ensure comparability and validity of the results, a general
preparation guide for “realistic” surfaces of polycrystalline chalcopyrite
thin films is highly desirable. We present results on wet-chemical cleaning
procedures of polycrystalline Cu(In1-xGax)Se2 thin films with an average x =
[Ga]/([In] + [Ga]) = 0.29, which were exposed to ambient conditions for
different times. The hence natively oxidized sample surfaces were etched in
KCN- or NH3-based aqueous solutions. By x-ray photoelectron spectroscopy, we
find that the KCN treatment results in a chemical surface structure which is –
apart from a slight change in surface composition – identical to a pristine
as-received sample surface. Additionally, we discover a different oxidation
behavior of In and Ga, in agreement with thermodynamic reference data, and we
find indications for the segregation and removal of copper selenide surface
phases from the polycrystalline material
Electron-beam-induced current at absorber back surfaces of Cu (In,Ga) Se2 thin-film solar cells
The following article appeared in Journal of Applied Physics 115.1 (2014): 014504 and may be found at http://scitation.aip.org/content/aip/journal/jap/115/1/10.1063/1.4858393The present work reports on investigations of the influence of the microstructure on electronic properties of Cu(In,Ga)Se2 (CIGSe) thin-film solar cells. For this purpose, ZnO/CdS/CIGSe stacks of these solar cells were lifted off the Mo-coated glass substrates. The exposed CIGSe backsides of these stacks were investigated by means of electron-beam-induced current (EBIC) and cathodoluminescence (CL) measurements as well as by electron backscattered diffraction (EBSD). EBIC and CL profiles across grain boundaries (GBs), which were identified by EBSD, do not show any significant changes at ÎŁ3 GBs. Across non-ÎŁ3 GBs, on the other hand, the CL signals exhibit local minima with varying peak values, while by means of EBIC, decreased and also increased short-circuit current values are measured. Overall, EBIC and CL signals change across non-ÎŁ3 GBs always differently. This complex situation was found in various CIGSe thin films with different [Ga]/([In]+[Ga]) and [Cu]/([In]+[Ga]) ratios. A part of the EBIC profiles exhibiting reduced signals across non-ÎŁ3 GBs can be approximated by a simple model based on diffusion of generated charge carriers to the GBs.This work was supported in part by the BMU projects comCIGS and comCIGSII. R.C. acknowledges financial support from Spanish MINECO within the program Ramon y Cajal (RYC-2011-08521)
Comparison of techniques for strain measurements in CuInSe2 absorber layers of thin-film solar cells
Orientation distribution mapping of polycrystalline materials by Raman microspectroscopy
Raman microspectroscopy provides the means to obtain local orientations on polycrystalline materials at the submicrometer level. The present work demonstrates how orientation-distribution maps composed of Raman intensity distributions can be acquired on large areas of several hundreds of square micrometers. A polycrystalline CuInSe(2) thin film was used as a model system. The orientation distributions are evidenced by corresponding measurements using electron backscatter diffraction (EBSD) on the same identical specimen positions. The quantitative, local orientation information obtained by means of EBSD was used to calculate the theoretical Raman intensities for specific grain orientations, which agree well with the experimental values. The presented approach establishes new horizons for Raman microspectroscopy as a tool for quantitative, microstructural analysis at submicrometer resolution
Retrospektive Evaluation eines Prognosemodells fĂĽr die Bettenbelegung durch COVID-19-Patientinnen und -Patienten auf deutschen Intensivstationen
Während der COVID-19-Pandemie waren bundesweite Daten zu den Kapazitäten der Gesundheits-versorgung und Krankenhäuser eine wichtige Orientierungshilfe für ressourcenstrategische und politische Entscheidungen. Im vorliegenden Beitrag wird die Leistungsfähigkeit eines Prognosemodells für die Bettenbelegung durch COVID-19-Patienten und -Patientinnen auf deut-schen Intensivstationen am Beispiel der fünf „Kleeblatt“-Regionen Deutschlands (Nord, Ost, Süd, Süd-West, West) im Zeitraum vom 1.7.2021 bis zum 2.1.2023 retrospektiv evaluiert. Außerdem werden Zeiträume mit außergewöhnlichen Abweichungen von prognostizierten und tatsächlichen Werten visualisiert und diskutiert.Peer Reviewe
Recent Developments in the Application of Baeyer-Villiger Monooxygenases as Biocatalysts
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