What are next generation solar cells?
Research is being carried out within SISER into the next generation of solar cell technology that go beyond the Shockley-Queiser limit. This limit corresponds to the maximum efficiency of a single junction solar cell (e.g. silicon). The reason that a limit exists is that a single junction solar cell can only absorb efficiently over a portion of the energy range emitted by the sun. Methods of going beyond the Shockley-Queiser limit include converting part of the unused solar radiation into an energy that can be absorbed by the solar cell. This is known as spectral conversion and can take the form of Up-conversion, Down-conversion and Down Shifting. Alternatively, a combination of materials can be used to provide a so called “intermediate band” which allows for additional absorption at lower energies.
What are the advantages of next generation solar cells?
The advantage of spectral conversion is that it can be easily integrated with current solar cell technology. Furthermore, the spectral conversion takes place in an electrically isolated layer that lies adjacent to the original solar cell. Therefore the optimised electrical properties of the single junction solar cell are not impeded.
The advantage of intermediate band solar cells is that high theoretical efficiency could be achieved; double that of a single junction solar cell. Furthermore, they are easier to fabricate than the more complex high efficiency tandem solar cells.
What are the challenges facing next generation solar cells?
The enhancement efficiencies of current spectral conversion layers for photovoltaic devices are very low. Therefore it is not yet economically productive to add these layers to a photovoltaic module. Understanding the mechanisms taking place in the spectral conversion process will allow for improved choice of materials and structures used to form the layers. Furthermore, by controlling the interaction of light with the layers, their efficiency can be increased.
Intermediate band solar cell efficiency suffers from non-ideal fabrication and the addition of an intermediate band material can induce structural damage. Developments in the fabrication methods of intermediate band solar cells are required to produce improved efficiencies. In addition, research into new intermediate band materials will enhance the technology.
Please click on the links below to learn more about the different types of next generation solar cells and the work being carried out by SISER researchers.