References of "Kretzschmar, Steffen"
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See detailOptical methodology for process monitoring of chalcopyrite photovoltaic technologies: Application to low cost Cu(In,Ga)(S,Se)2 electrodeposition based processes
Oliva, Florian; Kretzschmar, Steffen; Colombara, Diego UL et al

in Solar Energy Materials & Solar Cells (2016)

Non-destructive characterization of both single layers and completed devices are important issues for the development of efficient and low cost Cu(In,Ga)(S,Se)2 (CIGS) modules at high yields. This implies ... [more ▼]

Non-destructive characterization of both single layers and completed devices are important issues for the development of efficient and low cost Cu(In,Ga)(S,Se)2 (CIGS) modules at high yields. This implies for the need of methodologies suitable for the assessment of optical, electrical, and physico-chemical parameters that are relevant for the final device efficiency and that can be used for quality control and process monitoring at different process steps. In these applications, detection of in-homogeneities in the different layers from large area modules is especially relevant, being the presence of these inhomogeneities responsible for the existing gap between the efficiencies achieved in these technologies at cell and module levels. In this context, this work reviews the different optical methodologies that have been developed in the framework of the SCALENANO European project for the advanced assessment of the different layers in high efficiency electrodeposited – based CIGS devices. This has includes different strategies as those based on Raman scattering, Photoluminescence/Electroluminescence (PL/EL) based techniques and new photoelectrochemical based tools and firstly Raman spectroscopy is very sensitive to both composition and crystal quality parameters that are determining for device efficiency. Use of resonant Raman excitation strategies allows achieving a high sensitivity of the Raman spectra to the analysed features in the different regions of the device. This involves selection of the suitable excitation wavelength (in the broad spectral region from UV to IR) for the resonant Raman excitation of the required layer in the device. The strong increase in the intensity of the Raman peaks related to the use of resonant excitation conditions allows also decreasing the measuring time to times compatible with the implementation of these techniques at online process monitoring level. Analysed parameters include the electrical conductivity of the Al-doped ZnO window layer, the thickness of the CdS buffer layer and the chemical composition (S/(S+Se) relative content) and presence of relevant secondary phases as Cu-poor ordered vacancy compounds in the surface region of the absorbers. In addition PL/EL imaging are powerful techniques that provide direct access to the optoelectronic properties of the materials and devices. Whereas EL is performed using complete devices by injecting current in analogy to the operation of a light emitting diode, PL allows the characterization of bare absorber materials without the need for any functional or contacting layers. Moreover, semiconductor photo-electrochemistry (PEC) is a versatile technique that enables many opto-electronic properties of semiconductors to be determined. Essentially, a semiconductor on a conducting substrate placed in a solution containing redox species forms a Schottky barrier junction. The formation of such a diode enables basic semiconductor properties to be measured such as doping type, doping density, band gap and the flat band position versus the vacuum energy scale. In all these cases, quality control indicators suitable for the advanced assessment of these processes have been identified and validated for the electrodeposition-based processes developed at Nexcis Company. [less ▲]

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See detailRadiative recombination from localized states in CZT(S,Se) investigated by combined PL and TRPL at low temperatures
Kretzschmar, Steffen; Levcenco, Sergej; Just, Justus et al

in IEEE PVSEC proceedings (2016)

Detailed reference viewed: 89 (0 UL)
See detailQuantitative PL Imaging of Thin Film Solar Cells - Potential and Pitfalls
Redinger, Alex UL; Kretzschmar, Steffen; Unold, Thomas Ieee

in IEEE PVSEC proceedings (2016)

Photoluminescence imaging as well as quantitative photoluminescence spectroscopy has been successfully applied to different solar cell materials, such as crystalline silicon and polycrystalline Cu(In, Ga ... [more ▼]

Photoluminescence imaging as well as quantitative photoluminescence spectroscopy has been successfully applied to different solar cell materials, such as crystalline silicon and polycrystalline Cu(In, Ga) Se-2. These methods can be used to investigate spatial inhomogeneities as well as for the contactless determination of quasi-Fermi level splittings, which are related to the open-circuit voltage in finished photovoltaic devices. The theory underlying the analysis of quantitative PL imaging is found to work reliably for more ideal semiconductors such as silicon, but can pose substantial problems for the more non-ideal semiconductors such as kesterite-type materials, where both the optical properties as well as the recombination process may vary widely from sample to sample. In this contribution we will evaluate different approaches to analyse quantitative PL imaging and discuss the potential pitfalls incurred, especially when the actual sample temperature during the measurement is not properly taken into account. [less ▲]

Detailed reference viewed: 98 (0 UL)