RSE realized the world’s first InGaP/InGaAs/Ge/Ge quadruple junction (4J) device, with all layers deposited sequentially in the same MOVPE growth chamber, demonstrating that it is possible to overcome the cross-contamination problem between III-V and group IV elements of the periodic table.

The cross-contamination problem required the realization of such devices with two different deposition systems, doubling the investment costs, and therefore making their commercialization prohibitive. The result paves the way for highly efficient and cost-effective multi-junction solar cells whose materials can be combined with the same atomic constant, resulting in the lowest defect density.

RSE’s multi-junction cell also features a novel “transistor effect” architecture, which allows for modulation of current distribution between the different junctions and reduces losses. This milestone achievement is the result of a long research process, which involved, in addition to the “Ricerca di Sistema” funding, two different European projects, through which it was possible to acquire and optimize the MOVPE growth chamber to develop the new deposition processes.

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