Monitoring Aborber Crystallisation in Simulated Industrial Selenisation

Publieke samenvatting / Public summary

With demonstrated lab efficiency cell records up to 21%, PV modules based on CIGS (Copper Indium Gallium Selenide/Sulfide) are in principle able to compete with the dominant technology in the PV market, which is polycrystalline Silicon. And although under commercial production conditions modules are already realized with a viable efficiency/cost ratio, further improvement of this ratio is required. One of the key factors to improve the total efficiency/cost ratio, is the formation of the CIGS absorber itself. It is most cost effectively produced in two steps (“sequential processing”), by first depositing a CIG containing precursor, and then to expose it to selenium vapour at high temperature. Current state of the art often makes use of H2Se, which is hazardous, and expensive to use.

Goal of the project is to study the time dependent phase formation of CIGS by XRD for the first time under realistic process conditions, in order to improve layer quality (efficiency) and to reduce cost by optimizing both equipment layout, process parameters (process time), and their control.

Korte omschrijving
The Dutch company Smit Ovens is currently very successful in the market with an RTP based thermal treatment system, which is based on elemental selenium vapour. This is cheaper and less hazardous in use. Process time is greatly reduced, enabling in line production at atmospheric pressure. A pilot system for treatment of 30x30 system is installed at Solliance as part of a complete CIGS baseline, which is aiming at low cost full atmospheric processing, based on electrochemical precursor deposition.

The time dependent formation process of CIGS material phases and spatial distributions is insufficiently understood. The phase diagram of CIGS is very complicated, and the resulting material properties are, amongst others, highly dependent on the thermal treatment sequence and the variation of selenium pressure during this sequence. Good cell efficiencies well above 16% have been demonstrated by atmospheric process routes, but improved basic understanding of the relation between layer quality and varying process parameters and specific routes of precursor formation is highly desired.

With this improved efficiency/cost ratio, and the possibility to produce CIGS modules also on other building materials, this project supports the TKI Solar Thin film PV roadmap goals of more cost efficient PV, and of smart PV integration in building materials and components. On longer term, results of the project may also provide important background for the selenisation of copper zinc tin (CZTS) based absorbers, and of CIGS or CZTS-based high band gap materials for high efficiency PV concepts.