Programm Photovoltaik Ausgabe 2008 ... - Bundesamt für Energie BFE

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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 will improve the average and peak efficiency of the modules produced in the
manufacturing plants of 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 will contribute significantly to this objective by giving a frame for knowledge development,
know-how 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 materialand
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 project tasks will focus on:
(1) very high-quality modules manufactured by coevaporation 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: electrodeposition 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 coevaporation and the
electrodeposition approaches. All process developments such as modifications of the back contact,
wet- or vacuum-deposited buffer layers, the multi-stage coevaporation 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-solemnization 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, D. Brémaud, ETH Zurich
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