Project: New in-line optical methodologies for advanced assessment of high efficiency CIGS industrial processes

Acronym	In4CIS (Reference Number: JTC-2_2019_048)
Duration	01/01/2020 - 31/12/2022
Project Topic	In4CIS aims to establish and demonstrate at pre-industrial level optical advanced methodologies for the in-line assessment of advanced processes in Cu(In,Ga)Se2 (CIGS) thin film photovoltaic technologies. These will be applied to the monitoring of innovative postdeposition treatments (PDT) that are developed for the production of very high efficiency CIGS devices, in order to ensure a successful transfer of these CIGS process concepts from cell (lab) level to a pre-industrial module level. PDT processes are based in alkaline postdeposition doping treatments and have allowed achieving solar cells with reproducible efficiency values > 20% (with a record certified value of 22.6%), in the frame of the Sharc25 H2020 European project that was coordinated by the ZSW partner (http://sharc25.eu/). The successful transfer of these process concepts to pre-industrial module level requires for a detailed assessment of the uniformity of the processed layers when the processes are scaled from cell (cm2) to module (m2) device dimensions. Appearance of inhomogeneities in the layers when scaled to module dimensions constitutes one of the main reasons for the decrease of the efficiency of the modules in relation to that from the individual cells. Optimisation of the uniformity of the processes implies the need for high sensitivity tools and methodologies allowing the advanced assessment at in-line monitoring level of the uniformity of the processed layers, detecting at an early stage the appearance of in-homogeneities in the processed surfaces at the process line. This implies the need for non-destructive methodologies –as those based in optical techniques- allowing the fast inspection of the processed surfaces in the process line. The typical CIGS device architecture includes a Mo back contact (that is deposited on a glass substrate), the CIGS absorber layer (that constitutes the core of the photovoltaic device, absorbing most of the light that is converted into electricity), a nanometric buffer layer (typically CdS or Zn(O,S)) and the window layer that is formed by a transparent conductive oxide (TCO). Fig. 1 shows a schematic representation of the device structure. In these devices, the assessment of the uniformity of the PDT processes implies the need to monitor the uniformity of the surface region of the CIGS absorbers after deposition of the buffer layers in the device structure. Availability of suitable in-line monitoring tools is critical to ensure high throughput/high yield industrial processes as required for competitive CIGS PV production lines. The optical methodologies proposed in the project are based in the use of multi-wavelength excitation Raman scattering/Photoluminescence (PL) techniques for the advanced non-destructive quantitative assessment of the uniformity of the CIGS surface absorber region at different process steps in the CIGS production line. These methodologies are based in the use of resonant excitation strategies where the excitation light is close to an elemental transition –as the energy of the band gap- of the compound that is analysed by the Raman probe. This determines a strong increase –of orders of magnitude – of the efficiency of the Raman process, and this allows achieving a very high measuring sensitivity with fast measuring times - compatible with their implementation at in-line process monitoring level.
Network	Solar Cofund 2
Call	Solar Cofund 2 Joint Call

Project partner

Number	Name	Role	Country
1	IREC - Catalonia Institute for Energy Research Solar Energy Materials & Systems Group	Coordinator	Spain
2	Universitat de Barcelona Department of Electronic and Biomedical Engineering	Partner	Spain
3	Lenz Instruments	Partner	Spain
4	Center for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) Department of Photovoltaics: Materials Research	Partner	Germany
5	MANZ AG Business Unit Solar	Partner	Germany