Programm Photovoltaik Ausgabe 2009 ... - Bundesamt für Energie BFE

Introduction / project objectives
The overall objective of the project is to develop advanced manufacturing technologies for
Cu(In,Ga)Se2 (CIS or CIGS) thin-film solar modules both for the electrodeposition and coevaporation
approach. This comprises technology transfer from laboratory scale to enable large area industrial
production. The project will improve the manufacturing techniques for low-cost, stable, efficient CIS
thin film solar modules on large area. This includes work on the molybdenum back contact, the buffer
layer, the CIS absorber and the quality and process control. Special emphasis is placed on the
development of cadmium-free large-area modules and of electrodeposition methods for CIS
absorbers. Results of the work will be transferred from the laboratory scale to the operating (pilot)
manufacturing plants in Germany, Sweden and France.
The work in the project is aimed to help to improve the average and peak efficiency of the modules
produced by the industrial partners Würth Solar, Solibro and EDF. Modifications of the back contact
(process and composition) and doping of the absorber will contribute to these improvements. Existing
uncertainties concerning the stability of modules with alternative cadmium-free buffers will be
eliminated and the transfer of the processes to the manufacturing plant will be prepared.
To fulfill the conditions for rapid entrance in the industrial production there is a need to consolidate and
extend the results on one side and to increase the acceptability of the process on the other side. The
project contributes significantly to this objective by giving a frame for knowledge development, knowhow
exchange and cross-fertilizations between the groups and technologies involved in the project,
i.e. between co-evaporation and electrodeposition methods of CIGS formation.
Short description of the project
In order for the commercial production of large Cu(In,Ga)Se2 based modules on the multi-megawatt
scale to be successful, the processes must still be streamlined and optimized taking both economical
and ecological aspects into consideration. This project aims to support the development of this
material- and energy-saving thin-film technology so it can gain a foothold in the free photovoltaic
market. Promising laboratory results will be transferred to large-scale production, where the availability
of appropriate production equipment and very high material and process yields are of decisive
importance. Six universities and research centers and four companies are working closely together in
order to merge the physical understanding of the processes and the engineering know-how, both of
which are necessary for up-scaling the CIS technology to a marketable multi-megawatt production
volume. The overall project tasks are focused towards:
(1) very high-quality modules manufactured by co-evaporation of CIS and applying cost-effective
methods, efficiency > 13.5 % on 0.7 m 2 .
(2) the development of cadmium-free buffer layers for cadmium-free CIS modules on an area of up to
0.7 m 2 , efficiency > 12 %.
(3) and the development of a mid-term alternative: electro-deposition of low-cost CIS modules with
efficiency � 10 % on 0.1 m 2 (estimated cost < 0.8 €/Wp).
The consortium will transfer the molybdenum back contact sputtering know-how to a specialized
European large-area glass coater to provide substrates for both the co-evaporation and the electrodeposition
approaches. All process developments such as modifications of the back contact, wet- or
vacuum-deposited buffer layers, the multi-stage co-evaporation of CIS, or improved gallium
incorporation in electrodeposited absorbers will first be tested and evaluated on the laboratory scale.
Successful approaches will be up-scaled and transferred to three independent commercial CIS pilot
lines located in three different European countries. Novel process and quality control techniques must
also be developed and applied to reach these ambitious goals.
The contributions of the ETH Zurich to this project are:
� Investigation of Mo pre-selenization and Na doping methods and mechanisms
� Investigation of TiN and ZrN as back contact layer
� Introduction of a novel MoX/Mo back contact to enhance Mo stability
� ETHZ will develop a modified absorber without the need for a buffer layer for reduction of
production costs
� Correlation of I/V results of heated and light-soaked samples with growth process in order to
increase the device stability
LARCIS, A. N. Tiwari, ETH Zurich
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