Abstract:
Photovoltaics for use in energy conversions: From capturing the sun’s rays to transmitting power optically
Karin Hinzer
School of Electrical Engineering and Computer Science and Physics Department
University of Ottawa, Canada
Photovoltaic devices that are connected in series can become efficient DC-DC power converters for a multitude of application. Using tailored devices, 5 to 24 V devices can be obtained. As these are photonic devices, we observe no electromagnetic interference for those devices making them ideal for sensitive applications. In this talk, I will present specific designs used in photovoltaic applications and then move on to results on photonic power converters such as III-V semiconductor material properties required for these devices and the role of nanostructures to increase their maximum efficiencies. The discussion on device properties will include the role of luminescent coupling observed in the devices and how these can be predicted using calculations. We present results to explain how this boosts device efficiencies by approximately 70 mV per junction in GaAs devices. Luminescent coupling also increases efficiency in devices with four more junctions, however, the high cost of materials remains a barrier to their widespread use. Substantial cost reduction could be achieved by replacing the germanium substrate with a less expensive alternative: silicon. Threading dislocations introduced by the lattice mismatch between silicon and other layers have a detrimental effect on performance. In this research, we seek to accommodate lattice mismatch by introducing a voided germanium interface layer on the silicon substrate to intercept dislocations and prevent them from reaching the active layers. We present results exploring the effect of threading dislocations and substrate doping on device performance. Finally, I will discuss how to adapt photonic power converter designs to new concepts in photovoltaics.