At IMM-CNR Catania we use the plasmonic properties of noble metal nanoparticles (Au or Pt) to improve the photo-electro catalytic activity of n-type 3C-SiC/p-type Si heterojunction solar cells, to be used as photocathode for hydrogen generation from water.

Twofold effect is obtained: i) reduction of onset potential and ii) modification of saturated photocurrent. Reduction of onset potential is attributed to the catalytic effect, current variations to the plasmonic effects.

Figure 1: TEM micrograph in plan view of the 3C-SiC layer after deposition of Au: (a) NPs 1 by single immersion for 240 s; (b) NPs 2, by multiple immersions for a total immersion time of 180 s. Gold particles appear as black dots.

When large and thick Au grains (radius 55 ± 22 nm) are deposited (Au NPs1) the particles produce shadowing effect, decreasing the saturation current. By depositing smaller nanoparticles with tight distribution (radius 23 ± 5 nm) instead, the current increases, thanks to the plasmonic surface resonance, as demonstrated by external quantum efficiency (EQE) measurements, shown in Fig. 2. The Pt and the Au NPs2 samples have EQE spectra peaked in the UV and in the IR, respectively. The plasmonic resonance peak of Au nanoparticles with radius around 25 nm is known to occur at about 600 nm wavelength while in the case of Pt nanoparticles the resonance is at about 250 nm. Hence, the EQE spectra are clearly dominated by the plasmonic resonances of the noble metal nanoparticles, producing the observed increase of the saturated photocurrent.

Figure 2: External quantum efficiency of the sample covered with Pt or Au (NPs 2), measured without the electrolyte solution.

Contact: Stefania M.S. Privitera

Recent publications:

• Photo-electrochemical water splitting in silicon based photocathodes enhanced by plasmonic/catalytic nanostructures, T. Han, S. Privitera, R.G. Milazzo, C. Bongiorno, S. Di Franco, F. La Via, X. Song, Y. Shi, M. Lanza, S. Lombardo. Materials Science & Engineering B 225 (2017) 128–133.
• Formation, Morphology, and Optical Properties of Electroless Deposited Gold Nanoparticles on 3C-SiC, R. G. Milazzo, S. Privitera, G. Litrico, S. Scalese, S. Mirabella, F. La Via, S. Lombardo,