Development of compact micro-CPV modules using advanced packaging technologies based on high-performance solar cells

olar energy offers a sustainable solution to current energy and environmental challenges. III-V multi-junctions solar cells represent the photovoltaic technology with the highest effciencies among all solar technologies. Unfortunately, these cells are expensive. To reduce the cost of this technology, a concentrating optic can be placed above the cells, thereby reducing the amount of III-V materials needed. This strategy, known as concentrator photovoltaics (CPV), also increases the conversion efficiency of solar cells. However, CPV faces limitations such as resistive and thermal losses, as well as a lack of compactness, preventing its large-scale deployment. In response to these limitations, the miniaturization of CPV, referred to as micro-CPV, has been developing over the past several years. Reducing the cell size to below one millimeter decreases resistive losses, simplifes thermal management, and increases module compactness. To fully leverage the advantages of this technology, challenges related to micro-fabrication, packaging, and optics must be addressed. This thesis explores these three felds with the following goal : to fabricate a compact microCPV module with lightweight concentrating optics, using high-performance micro-solar cells while minimizing III-V material losses. The reduction in cell size increases the impact of perimeter recombinations, which decreases the open-circuit voltage (Voc) and thus the conversion efficiency. Sub-millimeter cells with low sensitivity to perimeter recombinations and Voc values exceeding those reported in the literature (to our knowledge) have been fabricated. A loss assessment related to non-radiative recombinations for each of the sub-cells (InGaP/InGaAs/Ge) was also conducted. This assessment demonstrated that the InGaP sub-cell is the most afected by perimeter recombinations. Reducing cell size also presents packaging challenges. Wire bonding, traditionally used for CPV, requires large busbars, generating signifcant shading losses for sub-millimeter cells. A new cell connection method has been developed to minimize shading losses. Throughout this thesis work, a lightweight and compact optic has been designed, fabricated, and characterized. This optic was used to create a prototype of a single module approximately 2 cm thick. Outdoor characterizations of this prototype have shown that integration losses in the module are less than 20%.

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