With the mounting evidence for man-made global climate change and our growing dependence upon fossil fuels – including an oil consumption rate which is 4× the oil discovery rate – more sustainable energy systems are required to meet our global present and future energy needs. The research and development of efficient alternative energy sources is essential for the progress toward a sustainable energy economy. This will include an array of renewable energy generation technologies, including hydroelectric, wind, biomass, geothermal, tidal, and solar powers. One of the leading candidates for large-scale efficient renewable energy production is solar power using photovoltaic systems which convert energy from the sun directly into electricity. Photovoltaic systems are sources of renewable energy that is freely available in all countries in the world. Importantly, environmental pollutants, such as greenhouse gas emissions, do not result from normal operation of photovoltaic systems. Therefore, any pollutants during fabrication can be carefully controlled on-site to minimize environmental impact, and these pollutants can be averaged across the 20+ years lifetime of the device.
The drive towards grid-parity (the cost of solar electricity equaling the cost of conventionally-generated electricity) has resulted in the development of several solar technologies, ranging from the low-cost low-efficiency (2-5%) devices (ex. organics), to mid-cost mid-efficiency (10-20%) devices (ex. silicon), and finally to the high-cost high-efficiency (30-40%) devices (III-V semiconductor materials). This latter category becomes economically competitive with all solar technologies through the introduction of concentrated photovoltaic technology, in which a large-area illumination is intensified onto a small-area solar device. Recent efforts on III-V semiconductor multi-junction solar cells have lead to efficiencies of >40% under concentrations of several hundred times the sun’s intensity on the Earth.
To realize the potential of solar photovoltaic energy systems, more efficient and cheaper devices are necessary. This may be achieved through improved designs, materials, growth, and manufacturing. The realization of this potential is the main goal of the SUNLAB.