Promising Proposal for Crystalline Silicon Bottom-Based Multijunction Photovoltaic Devices: Apertures in the Top-Cell Surface

Crystalline silicon (c-Si)-based multijunction (MJ) photovoltaic (PV) devices, such as III-V/c-Si and/or perovskite/c-Si MJ devices, are promising for future high-efficiency and low-cost PV systems that convert solar energy into electricity. The typical MJ designs suffer mostly from low current generation in the c-Si bottom subcells because of insufficient light passing from the top to them. We propose an innovative idea for c-Si-based MJ PV devices that includes open-area portions on the top-cell surface to improve light illumination to the bottom subcell and thus its current. Preliminary tests are being performed on four-terminal III-V/c-Si MJ devices, which include commercial flexible film triple-junction GaAs top cells and laboratory-made c-Si heterojunction bottom subcells. The open areas on the top surface are designed to retain the top's significant efficiency while maximizing the bottom's efficiency. As a result, the approximate performance of such a III-V/c-Si MJ structure is 31.8%. Future aspects of the concepts are thoroughly examined. With the accomplishments attained in this effort, there is an opportunity for additional hopeful progress.