Abstract
We study n-i-p amorphous silicon solar cells with light-scattering nanoparticles in the back reflector. In one configuration, the particles are fully embedded in the zinc oxide buffer layer; In a second configuration, the particles are placed between the buffer layer and the flat back electrode. We use stencil lithography to produce the same periodic arrangement of the particles and we use the same solar cell structure on top, thus establishing a fair comparison between a novel plasmonic concept and its more traditional counterpart. Both approaches show strong resonances around 700 nm in the external quantum efficiency the position and intensity of which vary strongly with the nanoparticle shape. Moreover, disagreement between simulations and our experimental results suggests that the dielectric data of bulk silver do not correctly represent the reality. A better fit is obtained by introducing a porous interfacial layer between the silver and zinc oxide. Without the interfacial layer, e.g. by improved processing of the nanoparticles, our simulations show that the nanoparticles concept could outperform traditional back reflectors.
Highlights
Thin-film silicon solar cells strongly rely on light-trapping schemes to achieve high efficiencies
We study n-i-p amorphous silicon solar cells with lightscattering nanoparticles in the back reflector
It appears that the correspondence is better for the grating reflector while the modelling results overestimate the performance of the plasmonic grating
Summary
Thin-film silicon solar cells strongly rely on light-trapping schemes to achieve high efficiencies. Due to their relatively low absorption in the near-infrared wavelengths, light management is necessary to enhance their photocurrent [1]. The conventional approach consists of growing silicon layers on a randomly textured substrate or transparent conductive oxide (TCO) layer [2,3,4,5]. Light scattering by metallic nanoparticles is an alternative and promising approach for light trapping. The scattering efficiency strongly depends on the nanoparticle size, as particles smaller than 30 nm tend more to absorb light than to scatter it [11]. Modelling results predict that plasmonic concepts can yield significant photocurrent enhancement in thin-film silicon solar cells [12,13,14,15,16,17]
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