University of Delaware - College of Engineering
ELECTRICAL & COMPUTER ENGINEERING

Research

Photonics & Electromagnetics

50% Efficient Solar Cells

Dennis Prather

The goal in this aspect of the program is to efficiently split broad band illumination from the sun into various channels of spectral bands wherein each band is laterally spaced relative to the others. In this case each band is incident on a solar cell, or stack of solar cells, that are specifically designed to efficiently convert that band into electrical energy. The zeroth order approach to achieving this is to use optical prisms. However, while this approach offers efficient and broad band splitting it will be difficult to render such an approach manufacturable and cost effective due to the need to have bulk optical devices that are polished and integrated on the device scale. Thus, our approach will be to use alternative dispersive devices that are amenable to large scale fabrication methods using thin film processes for ease of manufacture and economy of scale. To do this we will pursue two separate approaches, i.e., multiple order diffractives/gratings (MOD), and photonic crystal superprims. In the former case one uses a dispersive grating that is designed to operate over a very wide band by virtue of having a relief height that is proportional to several PI in phase. In so doing, the grating is rendered as a hybrid between a fully diffractive and fully refractive device, which offers extreme gains in bandwidth over conventional gratings. In addition, such an approach can be scaled to very high through put and low cost manufacturing techniques. The second approach is to use photonic crystal (PhC) based dispersion engineered devices that offer orders of magnitude of spectral splitting as compared to conventional prisms. This approach may be somewhat lower bandwidth of operation in comparison to the MOD but can possibly be made to operate over a large bandwidth with the addition of a MOD. In any case, we have recently developed very low cost PhC devices in polymers, which can also be scaled up to high through put and low cost manufacturing methods.


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