Advanced Characterisation of Chalcopyrite Electrodeposited SemiconductorS for Enhanced Devices


CALL: 2008

DOMAIN: MS - New Functional and Intelligent Materials and Surfaces





HOST INSTITUTION: University of Luxembourg

KEYWORDS: chalcopyrites, photovoltaics, electrodeposition, composition (profile), interfaces, structures

START: 2009-01-01

END: 2011-12-31


Submitted Abstract

The ACCESSED project will answer the question “How to make electrodeposited and annealed (EDA) chalcopyrite semiconductor materials being of the same quality as physical vapour deposited (PVD) material?”Annealing electrodeposited pre-cursors offers a low cost route to producing semiconductors, and can be used to make the chalcopyrite absorber layer copper indium gallium diselenide (Cu(In,Ga)Se2) in thin film solar cells. However, at present EDA has worse performance than other fabrication routes such as PVD. The best PVD Cu(In,Ga)Se2 solar cells have an efficiency of 19.9 %, whilst EDA Cu(In,Ga)Se2 solar cells are stuck at 11.5 %. Therefore to investigate the underlying differences between the two approaches chemical, structural, and interfacial comparisons of electrodeposited Cu(In,Ga)Se2 will be made alongside reference PVD material. New methods will then be found to increase the similarity of the Cu(In,Ga)Se2 material to the PVD material and thus improve overall efficiency of thin film devices made from EDA absorber layers.The compositional grading of the elements within the Cu(In,Ga)Se2 layers are of key importance in the world record cell and three different synthetic routes have been designed to try and achieve this with EDA material. The macro and micro-structure of the semiconductor are known to be important in terms of material quality. For PVD Cu(In,Ga)Se2 it is found that complete grains extending between both interfaces with a certain orientation give the best performance. Experiments will be conducted to investigate the grain size, boundaries, and orientation of the electrodeposited material. This information will be used to inform synthesis strategies to replicate the PVD grain structure. Experimental techniques to be used are SEM, XRD, Hall, SIMS, XPS, cathodoluminescence, and TEM.The effects of impurities on semiconductor performance are known to be critical but there are hardly any reports in the academic literature for Cu(In,Ga)Se2 semiconductors, and none at all for electrodeposited material. Investigations will be undertaken to quantitatively determine all the impurities within the electrodeposited and reference materials. Once the purity of the PVD reference material has been established experimental changes will be made to produce electrodeposited material with a similar or lower level of impurities. Impurities will be measured with ICP-MS, ion chromatography, and LC-MS.The interfaces of Cu(In,Ga)Se2 with the back contact molybdenum and the n-type material cadmium sulphide are extremely important for the electrical functionality of the device. Investigations will be made to see if the difference in morphology and structure of the PVD and electrodeposited Cu(In,Ga)Se2 affects the inter-diffusion of the elements at both interfaces. If significant differences are observed, experiments will be undertaken to try and control the diffusion processes at the electrodeposited films interfaces. Experimental techniques to be used are TEM, SIMS, EER, and XPS.All materials will be provided by the University. The electrodeposited material will be prepared by a PhD student, and the reference materials will be provided by PhD students and post-docs. Impurity and structural information will be obtained at the Centre de Recherche Public – Gabriel Lippmann with the help of their experts. Training will be provided for most of the techniques. Opto-electronic measurements will be made at the University.

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