11th International Conference on Transparent Optical Networks
Abstract
Although in principle very promising, photovoltaic technology has so far failed to deliver robust high efficiency
modules at affordable prices. Despite considerable research, high efficiency silicon based cells remain
expensive, while the more recent organic photovoltaics are still struggling with low efficiencies and short
lifetimes. Meanwhile, over the last few years, the study of localized plasmons [1,2] has also received great
attention due to the high field enhancements associated with confined fields , with a wide range of applications
possible, from optical switches to substrates for surface enhanced Raman spectroscopy (SERS).
Here we discuss how combining the structures normally used in photovoltaic devices with metallic cavities
supporting localized plasmons can lead to considerable improvements in the performance of solar cells. In
particular we show how by changing the shape and size of spherical voids on a metallic surface, one can tune the
plasmon modes to obtain significant absorptions across the solar spectrum [3]. By coating one such nanocavity
surface with a sub 100 nm-layer of semiconductor, we can create a nanostructured solar cell, where the localised
Mie modes efficiently couple light into the semiconductor layer. As the plasmons electric field enhancement is
largest very close to the surface, significant absorption can be maintained even when the semiconductor
thickness is reduced to below the typical exciton diffusion length. In addition minority carrier transport is
improved. That means we can beat the usual balance between light absorption and exciton recombination loses,
and so significantly increase the overall efficiency of the photovoltaic devices.
Keywords: plasmons, solar cells, nanostructured surfaces