Quantum theory of operation for rectenna solar cells

Optical rectennas, sub-micrometre antenna-coupled diodes, can directly rectify solar and thermal electromagnetic radiation, and have been proposed as an alternative to conventional semiconductor photovoltaics. We develop a comprehensive description of the operating principle of rectenna solar cells. In prior work classical concepts from microwave rectenna theory have been applied to the analysis of photovoltaic power generation using these ultra-high frequency rectifiers. Because of their high photon energy the interaction of petahertz frequency waves with fast-responding diodes requires a semiclassical analysis. We use the theory of photon-assisted transport to derive the current-voltage [I (V)] characteristics of metal/insulator/metal tunnel diodes under illumination. We show how power is generated in the second quadrant of the I (V) characteristic, derive solar cell parameters, and analyse the key variables that influence the performance under monochromatic radiation and to a first order approximation. The efficiency improves with reduced dark current under reverse bias and increasing incident electromagnetic power.