Breaking the Voltage Barrier for CdTe Solar Cells
Polycrystalline CdTe solar cells are a mass market product and have now achieved >21% efficiency, having being limited to <16.7% for more than a decade. This improvement has been generated through optimisation of the optical properties and contacts which has led to increases in the current (Jsc) produced but the voltage (Voc) of devices has not significantly improved from the level which was achieved over 20 years ago. This low Voc is strongly linked to grain boundaries within the CdTe semiconductor layer and is the primary performance barrier. The challenge now is to develop new process routes which can control the grain boundary behaviour and break the existing Voc limit. This would see achievable CdTe cell efficiencies surpass 25% and make CdTe solar cells one of the lowest cost sources of electricity production. This project will have a dual focus to i) identify new routes to control the properties of grain boundaries in CdTe solar cells thereby improving the Vocand ii) explore the underlying physics of grain boundaries and quantify their impact on working solar cells. The work will be primarily cell oriented, with all cells being produced in-house using the established high efficiency CdTe cell platform at Liverpool. The student will become an expert in complete CdTe solar cell fabrication and characterisation. In addition to standard optical and electronic cell characterisation methods the student will also be trained to use a range of electron microscopy techniques for grain boundary specific analysis.