Broadband absorption enhancement in ultra-thin crystalline Si solar cells by incorporating metallic and dielectric nanostructures in the back reflector

摘要

We propose a back-reflecting scheme in order to enhance the maximumachievable current in one micron thick crystalline silicon solar cells. Weperform 3-dimensional numerical investigations of the scattering properties ofmetallic nanostructures located at the back side, and optimize them forenhancing absorption in the silicon layer. We validate our numerical resultsexperimentally and also compare the absorption enhancement in the solar cellstructure, both with quasi-periodic and random metallic nanostructures. We havelooked at the interplay between the metallic nanostructures and an integratedback-reflector. We show that the combination of metallic nanoparticles and ametallic reflector results in significant parasitic absorption. We comparedthis to another implementation based on titanium dioxide nanoparticles whichact as a lambertian reflector of light. Our simulation and experimental resultsshow that this proposed configuration results in reduced absorption losses andin broadband enhancement of absorption for ultra-thin solar cells, paving theway to an optimal back reflector for thin film photovoltaics.