Atmospheric Cost Competitive Elemental Sulpho-Selenization for CIGS
Thin film Cu(In,Ga)(Se,S)2 (CIGSSe) photovoltaic modules, and also CdTe-based thin film modules, exhibit conversion efficiencies at the same level as multi-crystalline Si wafer modules. Due to the use of scarce and toxic materials in CdTe solar cells, CIGSSe technology has the largest potential among all thin film solar cell technologies to contribute significantly to the large scale production of photovoltaic energy. However, this potential can only be brought to market success when the cost in terms of €/kWh of delivered electricity is competitive with other technologies. Of the total stack of thin layers that make up a complete cell, the absorber layer of this type of PV (the CIGSSe layer) has the highest impact on both production costs and conversion efficiency. In the past decade the deposition routes have primarily been studied with a focus on the latter: an optimal cell performance. However, the current state-of-the-art fabrication processes are either using expensive and slow vacuum processes, or the deposition process is carried out using highly toxic and expensive gases in a slow batch oven process.
The ACCESS CIGS project, aims at the improvement of an industrial selenisation and sulphurisation process and tool, allowing fast and material efficient (-50% selenium consumption) atmospheric pressure CIGSSe deposition for high conversion efficiency (18%) PV cells leading to lower manufacturing cost (-5%).
The project, aims at the atmospheric pressure deposition of CuInGa stacks, followed by rapid, cost-effective large scale atmospheric pressure selenisation step in order to produce Cu(In,Ga)(Se,S)2 solar cells. For these objectives, the following topics will be addressed:
Thermal and plasma-assisted cracking of the selenium will be introduced, after which solar cells will be made based on cracked selenium (lower costs and higher efficiency)
The waste selenium will be recirculation within the selenisation tool, allowing direct reuse - the impact of this process on the solar cell efficiency is studied (lower costs)
Sulphur will be introduced to the surface of Cu(In,Ga)Se2 layer in order to increase the open circuit voltage and therefore the power conversion (higher efficiency)
Quantitative goals are realisation of solar cell and module efficiencies of 18% and 16% respectively, while lowering manufacturing costs (-5%) and selenium consumption (-50%).
Optimization of this process will make this selenisation route more economically feasible, which will allow Smit Ovens to show the possibilities of their selenisation tool, while it will help TNO, PVcomB and TNO to produce high efficiency PV for a competitive price.