Tuning Plasmon Resonances for Light Coupling into Silicon: a “Rule of Thumb” for Experimental Design

Abstract

For Si thin-film solar cells to become efficient, schemes to increase the optical absorption in the films are necessary. Scattering of light using plasmonic resonances in metal nanoparticles has been suggested as a feasible route. When placed on a dielectric layer on the front of a solar cell, such metal nanoparticles can scatter a large fraction of the incident light into the solar cell at the resonance wavelength, and hence increase the light collection. However, many related effects may lead to a reduction in photocurrent. Thus, nanoparticle plasmon resonances must be optimized in order to improve the overall light collection. From an experimentalist’s point of view, simple and fast experimental design tools should be explored. In this work, we investigate the plasmon-related photocurrent enhancements for Si test-solar cells with a number of different metal nanoparticle shapes and materials placed on top of a dielectric layer. The spectral position of the photocurrent-enhancement onset is compared to plasmon resonance calculations based on a fairly simple model. Despite the fact that the optical interactions in nanoparticle solar cell configurations can be quite complex, the photocurrent enhancement in the investigated test-solar cells can be predicted qualitatively well for particles with a plasmon resonance in the visible spectrum. This simple and fast model can be used as a rule of thumb in designing nanoparticle arrays for a specific photocurrent enhancement profile.