Abstract
The ultimate limit for solar power conversion stands at 87% so there would appear to be plenty of scope for improving the efficiency of photovoltaic technology. The fastest route to achieving high power conversion efficiency is by stacking multiple photovoltaic junctions; the InGaP/GaAs/Ge multi-junction solar cell represents the industry standard for space and solar concentrator applications. However, the evolution of the technology to a 4J architectures is presently at a crossroads. Options exist to fabricate a lattice-matched 4J cell using dilute nitride semiconductors or strain-balanced quantum wells, or alternatively lattice mismatched and wafer bonding approaches have also proven to be effective; the latter holding the present world record of 46.5%. All these technologies are likely to achieve efficiencies in excess of 50% in the near term.
A more difficult question is the extent to which the cost of the multi-junction solar cell can be reduced. While options exist for high throughput manufacturing, it is here that alternative approaches to high efficiency might, ultimately hold an advantage. A perspective on the present status of intermediate band and hot carrier cell concepts will be given.
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Brief Bio
Dr. Ned Ekins-Daukes is Reader in Physics and Royal Society Industry Fellow at Imperial College London. His research is concerned with high efficiency photovoltaic energy conversion, spanning III-V solar cells, intermediate band and hot carrier concepts as well as PV-thermal systems. Ned was previously Lecturer at the School of Physics at the University of Sydney in Australia and prior to that a JSPS research fellow at the Toyota Technological Institute, Japan. He holds PhD and MSc degrees in Semiconductor Physics from Imperial College London and a degree in Physics & Electronics from the University of St Andrews in Scotland.
