Photovoltaic cells comprising two photovoltaic cells and two photon sources

Abstract

A photovoltaic device comprises an upper cell and a lower cell separated by an electrically insulating layer. The cells and the layers are fabricated as a single monolithic structure, and separate electrical contacts are provided for the upper and lower cells to allow independent extraction of current from each cell. The upper cell has a larger bandgap than the lower cell so that incident low energy photons unabsorbed and unconverted by the upper cell can propagate through to the lower cell for conversion. The two bandgaps can be selected to accommodate spectral' ranges of interest. The device is incorporated into a system including two sources of photons with different wavelength ranges associated with the bandgaps of the two cells, such that each cell can convert photons from one source. One source may be the sun and the other may be a local photon source such as a thermal source. Alternatively, both photon sources may be local sources. Operation of the device can be further optimised and extended by configuring the upper cell as a tandem cell or in a MIMS arrangement, or both.

Description

technical field [0001] This invention relates to photovoltaic cells. Background technique [0002] Power generation from photovoltaic cells has been a fact for many years, however, this does not constitute a significant part of the overall power generation. One reason for this is that photovoltaic power generation is more expensive than conventional power generation, mainly because the cost of a single photovoltaic cell is relatively high. There are two methods that can be used to reduce costs. One option is to make these cells from cheaper materials, but this usually results in lower conversion efficiencies. Alternatively, battery efficiency can be improved. High-efficiency cells can be used in solar concentrators (where light from the sun is collected over a large area and concentrated onto a small area of ​​photovoltaic cells), or in thermo-photovoltaic systems (where light is generated from sources such as fuel burning These cells are irradiated with high-intensity l...

AI Technical Summary

Problems solved by technology

This means that, for most of the time, these individual cells cannot be current matched and the device efficiency drops from the recorded optimum under the conditions of the designed illumination spectrum

Also, temperature variations are important in collector systems, so cell bandgap variations will mean that efficiency drops from the optimum value for current matching

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