Today’s energy policies are based on three requirements: the energy should be (i) secure, (ii) affordable and (iii) sustainable. The use of photovoltaic (PV) silicon solar cells has grown rapidly at a rate of 40% per year over the past decade. However, this rapid growth is mainly as a result of government subsidies and a reduction in the cost of PV silicon-based solar cells. Therefore, it is unsustainable financially, and also because the silicon used in the PV solar cells is unable to provide the required energy conversion efficiency alone (i.e. the ability to convert solar energy to electrical energy).
Multi junction solar cells (MJSC) are solar cells made of layers of different semiconductor materials. They are designed so that each junction of materials produces an electric current in response to different wavelengths of solar light. The use of multiple semiconducting materials in MJSC allows the absorbance of a broader range of wavelengths, improving their ability to convert sunlight to electrical energy when compared with existing PV silicon solar cells.
Prior to this project, the materials that made up MJSCs enabled a solar energy conversion efficiency of up to 44 %. However, if MJSCs are to be able to compete with traditional energy sources (i.e. nuclear, coal etc), their efficiency needs to reach at least 50 %. This project reduced the cost of generating electricity from PV by developing the metrological tools required to increase the efficiency of current MJSCs, while improving manufacturing processes and materials. This will enable the production of the next generation of solar cells using MJSCs.