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Project Name: A New Class of Tandems: Optically Coupled III-V/Silicon Module with Outdoor Efficiency Exceeding 30%
Funding Opportunity: PVRD-SIPS
SETO Subprogram: Photovoltaics
Location: Tempe, AZ
Award Amount: $213,335
Awardee Cost Share: $23,730
Project Investigator: Zachary Holman

This project utilizes a new class of tandem solar module to optically couple III-V and silicon cells into a module with outdoor efficiency exceeding 30%. In the proposed system, low-energy light will be collected and converted using silicon cells with the high-energy light being reflected and concentrated using a dichroic mirror onto a III-V cell. The system decouples the tandem components and utilizes concentration to increase the system efficiency and decrease the cost of energy.

Approach

The research team is developing the PVMirror, which is a curved silicon photovoltaic (PV) module that incorporates a spectrum-splitting optical coating. Infrared photons with energy near the bandgap of silicon are transmitted through the coating, absorbed in a silicon PV cell, and converted to electricity with high efficiency. Visible photons, however, are reflected by the coating and absorbed in a gallium arsenide cell located at the focus of the PVMirror, then converted to electricity with higher efficiencies than a silicon cell. This design has technological advantages over other tandem PV designs because the sub-cells do not need to be current matched, lattice matched, or process compatible, and the tandem converts some diffuse light into electricity.

Innovation

The PVMirror tandem module with silicon and gallium arsenide can potentially achieve 30% efficiency in outdoor conditions, which would break the current world record for this type of tandem, silicon-based configuration. This research will open the door to future PVMirror tandems that couple silicon with inexpensive thin-film materials.