Power over fibre: material properties of homojunction photovoltaic micro-cells

A comparison of the conversion efficiency from optical power to electrical power for three common material homojunction photovoltaic micro-cells was performed. The device widths were varied as a function of incident wavelength such that optimum power conversions were determined whilst under illumination of monochromatic light. GaAs is the most effective material as optimum devices can be fabricated as thin as 15um thick with conversion efficiencies as high as 59%. However, GaAs is extremely expensive and has a limited wavelength response. Although Ge has the lowest conversion efficiency of 36%, it is the only material simulated that is responsive under illumination of long wavelengths above 1.0um, and may be particularly useful for specific applications as it is efficient at both 1310nm and 1550nm, where the attenuation in silica fibres is minimal. Si is a commercially viable material for the use as a photovoltaic power converter (PPC) with conversion efficiencies as high as 43% at 980nm. Lasers at this wavelength are extremely cheap to produce, as well as the cost of Silicon PPCs being minimal.