Advanced 3D back-contact cell interconnection technology for next-generation smart modules

Currently, most photovoltaic panels around us integrate Si solar cells; current module technology is based on stringing (electrical series connection) of cells with an electrical contact at the top and bottom of the cell, and their subsequent lamination for encapsulation between a glass plate and a back plate. Increasing performance and production volumes are the main drivers for continuously lowering the cost of PV and are indispensable for its wide application. In addition to the steady progress in the efficiency of silicon cells with front and back contacts, other Si-based cell technologies, based on electrical contacts solely at the back of the cell, are being developed, potentially achieving even better cell efficiencies and enabling better performance at module level. However, their performance is compromised when integrated into modules, in terms of cost and reliability.

Within this technology domain, imec introduced an advanced interconnection technology based on a multi-functional fabric with 3D structure that combines multiple electrical conductors and encapsulating materials. This new approach enables low thermal-mechanical stress cell interconnection at a lower cost and limited use of materials. Moreover, it aims to improve electrical and reliability performance. This approach can also simplify the production of back-contact modules by reducing process steps and material consumption. Last but not least, cost and aesthetics make this interconnection concept even more attractive for a wide variety of back-contact module designs, for example in application areas such as Building Integrated (BI)PV. Compatibility with bifacial back-contacted cells (cells that collect light from both sides) enables further improvements in module efficiency. Specifically related to this proprietary interconnection technology, the integration of passive electronic components is studied to improve module operation (e.g. in changing illumination conditions), with cost reduction at PV system level, additional system flexibility and improved performance.

In this PhD topic, the aim is to further the research on imec's own "3D" woven interconnection technology and explore and evaluate different options for the integration of passive components (e.g., inductors, capacitors) as a first step towards smart power management of modules. Related to this, an essential aspect is to develop methodologies for the evaluation of these different configurations. This partly requires developing different interconnection structures, and investigating their compatibility (material, process, and characteristics) with PV module technology and required functionality. The various aspects of this research are assessed and evaluated with proof-of-concept modules and tested for reliability and relevance. In addition, thorough electrical characterization is required. An important part of the work will also consist of new material research, implementation, and assessment of industrial relevance, compared to other technologies in this field.

To support research in this area, our laboratory facilities provide processing and characterization equipment beyond the state-of-the-art in module research, development and manufacturing, and access to in-house knowledge and expertise to adequately assess samples and systems, ranging from material characterization and analysis to full module performance measurements and reliability testing. In addition, we are also actively building an ecosystem of partners (research institutions and companies) to further develop our knowledge and expertise in relevant applications for PV module integration. This includes several EU and local projects with multiple partners on various topics related to BIPV, VIPV, space PV and utility PV systems.