Within the duration of 36 months, the proposed project’s ambition is to develop advanced materials for the fabrication of novel architectures of Cu(In,Ga)Se2 (CIGS) photovoltaics (PV) and demonstrate them in an industrially relevant environment. The project aims to:
(1) Attain thin (≤ 200 μm thick) insulated steel substrates fit for upscaling. These will allow monolithically integrated flexible solar cells/modules. It will satisfy the IEC61646 standard (40 MΩ.m² between substrate and the rear cell/module contact for > 0.1 m²), and – as compared to high-quality steel substrates used for PV today – a 40 % reduction in substrate cost is foreseen. Production equipment will be used to establish the advanced steel substrate on a pre-industrial 20 cm-wide coil, which will allow rapid upscaling to larger industrial coils.
(2) To validate an industrially feasible process for rear CIGS surface passivation layers. An approach to reduce interface recombination at the rear CIGS absorber layer surface has already been proven at the lab scale. It combines a dielectric layer, which electrically ‘passivates’ the rear CIGS surface, with closely-spaced (1-2 μm pitch) nano-sized (100-300 nm) point openings for electrical contacting. Using such interface passivation layers, rear surface recombination is reduced by 98 % compared with the standard rear-contact/absorber-layer (Mo/CIGS) rear interface. The focus will be on Al2O3 passivation layers and patterning techniques, which can be scalable for the contact openings as nano-imprint lithography and nano-particle lift-off techniques in line with an increase in TRL from 4 to 6.
(3) To implement cost effective light management approaches for CIGS solar cells, using highly-reflective metals, nanostructures or nanostructured electrodes to overcome absorption losses in the case of ultra-thin absorption layers. Simple flat rear reflectors have been developed by members of the consortium on small-area solar cells but light scattering is needed for above 90 % absorption also for 500 nm thick CIGS layers and needs to be implemented on large-area solar modules. The focus will be on industrially viable deposition and nano-structuring techniques, based on state of the art nanotechnology.
(4) To obtain an optimized and scalable process for ultra-thin (500 nm) CIGS absorber layers, with low defect density and suitable bandgap profiling. The nano-patterned highly-reflective rear contacts and surface passivation layers described above are required to overcome absorption losses in the case of such ultra-thin absorber layers and will result in about 80 % reduction in CIGS material usage. Alkali metal supply (Na, K) strategies will be optimized for the novel device architectures, which maximizes efficiency and long-term stability. A proof-of-concept will be developed at an industrial scale and the ultra-thin CIGS absorber layers will be established in both co-evaporation and sputtering production tools by the industrial partners.
(5) To combine (1)-(4) in at least one fully integrated module demonstrator concept at TRL level 6 using industrially viable techniques. The demonstrator should have an exploitable market potential for BIPV as validated by a panel of end-users and stake-holders and based on market analysis. Note that several of the expected results (1)-(4) may have a commercial value separately and can be commercialized early on in the project.