Most photovoltaic panels around us integrate crystalline Si solar cells, and this technology will continue to dominate the PV market for the foreseeable future. Increasing performance and production volumes are the main drivers of continued cost reduction in PV, and are indispensable for their broad deployment. Steady progress in crystalline silicon cell efficiencies pushed record values over to 26%, however their performance is compromised upon integration into module. Current module technology is based on stringing of cells for electrical interconnection, and their subsequent lamination for encapsulation between a glass plate and a backsheet. Untapped potential of advanced materials and novel low-stress interconnection technologies in module fabrication is key to continued performance improvement in PV panels. With these goals imec investigates a novel multi-wire approach for back-contact cell interconnection. Our patented technology combines multiple functions of PV module level metallization, insulation of opposite polarities and encapsulation in one woven sheet. This concept also aims to combine soldering and lamination in one step, which would considerably simplify module assembly. With these elements it is considered highly innovative approach in in the PV field. This Phd aims to select/develop the adapted materials, process to at the end demonstrate the industrial viability of this concept.
Challenges to be tackled in this PhD lie in optimal material selection linked to the constraints of combined encapsulation and solder process. While numerous other boundary conditions on material properties are linked to their function in the module as packaging material. That means that performance loss must be minimal, while guaranteeing a durability of 25+ years. Last but not least, the solution must remain cost-competitive. Investigation will start with low temperature solder alloy and their adhesion to screen-printed and platted metallization. The mechanical strength and structural characterization (SEM-EDX, XRD, AFM) of the solder joint will provide critical feedback on its quality. Interaction between the solder in its molten state with the encapsulant will be equally subject of the study: to detect any potential negative impact on the adhesion, permeation and transparency of the encapsulant. These investigations will rely on in-situ opto-electrical imaging, and detailed post-mortem characterization to detect early stage failures. This technology design follows the principle of “Design for reliability” approach proven in the field of micro-electronics, still novel in photovoltaics. Another key to the success of this technology will be its insulation property that will arise from an ingenious weaving pattern between the two materials. Imec in-house weaving expertise, tools and collaboration with its close industrial partners will be essential.
In conclusion, close interaction with in-house cell design and processing, module technology and characterization experts will assist the Phd candidate. The new state-of-the-art module assembly line in EnergyVille with industrial laminator and cell pick-and-place tool as well as complete reliability and module characterization lab will be leveraged in the project.
Type of work: 15% literature study, 85% experimental
Supervisor: Jef Poortmans
Daily advisors: Eszter Voroshazi, Tom Borgers
The reference code for this PhD position is SE1712-16. Mention this reference code on your application form.