Inverted designs for CdTe solar cells
Polycrystalline thin-film CdTe solar cells are a mass-market product, have now achieved >22% solar conversion efficiency and are the lowest cost-per-watt technology, being cost competitive with fossil fuels. Despite this achievement they still fall far below their >30% efficient potential due to low voltage generation. This limitation stems from the inability to dope the p-type CdTe absorber layers in excess of 1015cm3 and associated problems with producing Ohmic contacts. In fact p-type material is chosen mainly since it is compatible with n-type transparent conductors in the present day standard design. We think it should be possible to make a radically new design of solar cell based on n-type material: Since CdTe can be n-doped up to 1017cm3 and has no contacting problems, this would get around the voltage limitations. You will design and make these new cells. Most of the work will be experimental but some simulations will be required for the design stage. This project will involve i) using SCAPS (Poisson solver for thin film PV) to identify heterojunction partner layers and contacts for new solar cell architectures based on n-type CdTe absorbers. ii) develop n-doping routes for thin-film CdTe, this could be either post-growth or during deposition and iii) demonstrate, develop and analyse working PV devices having the new architectures. The work will involve all aspects of device making, materials deposition and simulation work. All films and cells will be produced in-house using the established high efficiency CdTe cell platform at Liverpool. You will become an expert in complete CdTe solar cell fabrication and characterisation. In addition to standard optical and electronic cell characterisation methods you will also be trained to use a range of analysis techniques.