High-Efficiency Multijunction Photovoltaics

This Task Group focuses on novel approaches to InGaN and multijunction photovoltaics for unprecedented high photovoltaic energy conversion efficiencies. This goal requires development of new techniques for the efficient simultaneous coupling of electrons and photons through the various junctions. Figure 1 shows a device architecture that is one of the goals of the project: a five-junction (5J) solar cell using a high-bandgap InGaN top junction in combination with a fully lattice-matched underlying arsenide-phosphide four-junction (4J) cell. The figure shows the variety of techniques brought to bear on the challenge of simultaneous optical, electrical, and mechanical coupling of the junctions. The techniques developed by CEEM provide many degrees of freedom in the design of multijunction cells, yielding a very rich field of possible device architectures of which Fig. 1 represents only one example; others, including the use of inverted metamorphic multijunctions under the InGaN top junction, are being studied by CEEM as well.



Figure: Cross-sectional schematic of hybrid InGaN/arsenide-phosphide five-junction cell. Elements addressing the challenges of electrical, octical, and mechanical/termal coupling are indicated in the figure.

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