312 research outputs found
Proceedings of the EMRS 2010 Spring Meeting Symposium M: Thin Film Chalcogenide Photovoltaic Materials Strasbourg, France Preface
No full textSymposium M of the 2010 E-MRS was the 10th in the series of symposia on “Thin Film Chalcogenide Photovoltaic Materials”, which alternate yearly between the E-MRS Spring Meeting in Strasbourg and the MRS Spring Meeting in San Francisco. With close to 250 contributions, this symposium was very successful and has reached a new record of participants showing the dynamics of the scientific community developing and characterizing chalcogenide thin-film materials and solar cells
Structural and chemical investigations of CBD- and PVD-CdS buffer layers and interface in Cu(In,Ga)Se2-based thin film solar cells.
No full textIt is known that high-efficiency thin film solar cells based on Cu(In,Ga)Se-2 (CIGS) can be obtained using US buffer layers grown by chemical bath deposition (CBD). The highest efficiencies achieved with US buffer layers produced by physical vapor deposition (PVD) are significantly lower. To find reasons for this difference, structural and chemical properties of CBD- and PVD-CdS buffer layers and their interfaces with CIGS were investigated by means of bright-field (BF-TEM), high-resolution (HR-TEM) and energy-filtered transmission electron microscopy (EF-TEM), and also by energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). PVD-CdS grains were shown to be clearly larger than the CBD-CdS grains. Also, a large defect density was detected at the PVD-CdS/CIGS interface, which is attributed to the larger lattice mismatch than at the CBD-CdS/CIGS interface. Cu diffusion from CIGS into CdS was found for the CBD- and the PVD-CdS sample. The PVD-CdS/CIGS interface turned out to be quite abrupt, whereas the CBD-CdS/CIGS interface is rather diffuse. The differences in efficiencies of solar cells with CBD- and PVD-CdS buffer layers can partly be explained by referring to the higher defect density and the probable absence of an inversion of the near-interface region from p- to n-type at the PVD-CdS/CIGS interface
Development of Thin Film Cu(In, Ga)Se2 and CdTe solar cell
No full textCu(In,Ga)Se-2 and CdTe heterojunction solar cells grown on rigid (glass) or flexible foil substrates require p-type absorber layers of optimum optoelectronic properties and n-type wide-bandgap partner layers to form the p-n junction. Transparent conducting oxide and specific metal layers are used for front and back electrical contacts. Efficiencies of solar cells depend on various deposition methods as they control the optoelectronic properties of the layers and interfaces. Certain treatments, such as addition of Na in Cu(InGa)Se-2 and CdCl2 treatment of CdTe have a direct influence on the electronic properties of the absorber layers and efficiency of solar cells. Processes for the development of superstrate and substrate solar cells are reviewed
Characterization of Grain Boundaries in Cu(In,Ga)Se Films Using Atom-Probe Tomography
No full textThis paper discusses the advantages of pulsed laser atom-probe tomography (APT) to analyze Cu(In,Ga)Se-2-based solar cells. Electron backscatter diffraction (EBSD) was exploited for site-specific preparation of APT samples at selected Cu(In,Ga)Se-2 grain boundaries. This approach is very helpful not only to determine the location of grain boundaries but also to classify them as well. We demonstrate that correlative transmission electron microscopy (TEM) analyses on atom-probe specimens enable the atom-probe datasets to be reconstructed with high accuracy. Moreover, EBSD and TEM can be very useful to obtain complementary information about the crystal structure in addition to the compositional analyses. The local chemical compositions at grain boundaries of a solar grade Cu(In,Ga)Se-2 film are presented here. Na, K, and O impurities are found to be segregated at grain boundaries. These impurities most likely diffuse from the soda lime glass substrate into the absorber layer during cell fabrication and processing. Based on the experimental results, we propose that Na, K, and O play an important role in the electrical properties of grain boundaries in Cu(In,Ga)Se-2 thin films for solar cell
Comprehensive Comparison of Various Techniques for the Analysis of Elemental Distributions in Thin Films Additional Techniques
Get PDFIn a recent publication by Abou Ras et al., various techniques for the analysis of elemental distribution in thin amp; 64257;lms were compared, using the example of a 2 m thick Cu In,Ga Se2 thin amp; 64257;lm applied as an absorber material in a solar cell. The authors of this work found that similar relative Ga distributions perpendicular to the substrate across the Cu In,Ga Se2 thin amp; 64257;lm were determined by 18 different techniques, applied on samples from the same identical deposition run. Their spatial and depth resolutions, their measuring speeds, their availabilities, as well as their detection limits were discussed. The present work adds two further techniques to this comparison laser induced breakdown spectroscopy and grazing incidence X ray amp; 64258;uorescence analysi
Properties of CIGS Solar Cells Developed with Evaporated II-VI Buffer Layers
No full textThe CIGS layers were grown with a vacuum evaporation method. The CdS was deposited by a high vacuum evaporation (HVE) method at different substrate temperatures and post deposition treatments were applied. Properties of different CdS layers are characterized and the analyses of the current-voltage and spectral response measurements have been performed to identify the differences of CBD and PVD processes.
ZnS and ZnSe buffer layers were applied as an alternative to CdS. Layers of different thickness were grown by e-beam (EB) and thermal evaporation (VE) at different substrate temperatures (RT to 400 °C). A post-deposition annealing was applied in order to
control the diffusion of Zn into the CIGS. Upon light soaking, increase in Voc and FF are measured
Characterization of Cu (In x, Ga y) (S m, Se n) 2 thin-film solar cell materials by Raman microscopy
No full textPreface
No full textSymposium B of the 2012 E-MRS was held in the Palais de Congrès in Strasbourg, France in May, 2012 and was the 11th in a series of symposia on “Thin Film Chalcogenide Photovoltaic Materials”
Microscopic origins of radiative performance losses in thin film solar cells at the example of Ag,Cu In,Ga Se2 devices
Get PDFThe present work provides an overview of radiative performance losses in thin film solar cells, focusing on those related to the open circuit voltage, using Ag,Cu In,Ga Se2 devices as examples. The microscopic origins of these losses are outlined, highlighting the presence of compositional variations, strain, and inhomogeneously distributed point defects on various length scales as contributors to band gap and electrostatic potential fluctuations, which both make up for the broadening of the absorption edge in the absorptance or quantum efficiency QE spectra of the semiconductor absorber layer or the completed solar cell device. The relationship between this broadening and Urbach tails is discussed. It is shown that the photovoltaic band gap energy as well as the broadening can be determined reliably from the arithmetic mean and standard deviation extracted from Gaussian fits to the first derivative of the absorptance or quantum efficiency spectra around the absorption edge. The more enhanced the broadening, the more shifts the local maximum in the luminescence spectrum to smaller energies with respect to the band gap energy of the absorber layer, as verified for about 30 Ag,Cu In,Ga Se2 solar cell
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