I did some work in this area about a decade ago. The issues I ran into involved converting the energy into something that can be stored. If semiconductors are

I did some work in this area about a decade ago. The issues I ran into involved converting the energy into something that can be stored. If semiconductors are used for detection/rectification, the band-gap voltage must be overcome before any energy is recovered. Specialized devices with very low band-gap voltages are available, but losses are still significant.