Light harvesting with multiwall carbon nanotube/silicon heterojunctions

Paola Castrucci, Claudia Scilletta, Silvano Del Gobbo, Manuela Scarselli, Luca Camilli, Mirko Simeoni, Bernard Delley, Alessandra Continenza, Maurizio De Crescenzi

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

We report on a significant photocurrent generation from a planar device obtained by coating a bare n doped silicon substrate with a random network of multiwall carbon nanotubes (MWCNTs). This MWCNT/n-Si hybrid device exhibits an incident photon to current efficiency reaching up to 34% at 670 nm. We also show that MWCNTs covering a quartz substrate still exhibit photocurrent, though well below than that of the MWCNTs coating the silicon substrate. These results suggest that MWCNTs are able to generate photocurrent and that the silicon substrate plays a fundamental role in our planar device. The former effect is particularly interesting because MWCNTs are generally known to mimic the electronic properties of graphite, which does not present any photocurrent generation. On the basis of theoretical calculations revealing a weak metallic character for MWCNTs, we suggest that both metallic and semiconducting nanotubes are able to generate e–h pairs upon illumination. This can be ascribed to the presence of van Hove singularities in the density of states of each single wall carbon nanotube constituting the MWCNT and to the low density of electrons at the Fermi level. Finally, we suggest that though both MWCNTs and Si substrate are involved in the photocurrent generation process, MWCNT film mainly acts as a semitransparent electrode in our silicon-based device.
(Some figures in this article are in colour only in the electronic version)
Original languageEnglish
JournalNanotechnology
Volume22
Number of pages8
ISSN0957-4484
DOIs
Publication statusPublished - 4 Feb 2011
Externally publishedYes

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