Light harvesting with multiwall carbon nanotube/silicon heterojunctions

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.

3D Carbon Nanotube Networks as Mechanical, Electrical and Photovoltaic Transducer and Superhydrophobic Filter

“…These peaks are located at 6 eV and 24.5 eV respectively, and are downshifted in energy loss with respect to those of highly oriented pyrolytic graphite (7 eV and 28 eV, respectively). This is due to the low dimensionality of the system, as already found for multi-walled CNTs [12].…”

Effect of multiwalled carbon nanotubes incorporation on the performance of porous silicon photodetector

“…It exhibits two peaks of response; one at 650 nm is originated from the porous structure absorption edge, while the other is at 900 nm due to absorption edge of bulk silicon. The high photosensitivity of MWCNTs-incorporated porous silicon photodetector can be ascribed to the large surface area and short diffusion length of photo-generated carriers after adding the MWCNTs [16]. The obtained values of responsivity is higher than that for porous silicon reported in literatures [17][18][19].…”

Synthesis of Nanosphere -Fe2O3/MWCNT composite as Photo-catalyst for the Degradation of Rhodamine B

“…After combination with MWCNTs, the Fe 2 O 3 /MWCNT composite shows a weak Raman shift, which demonstrates the existent direct interaction between MWCNTs and Fe 2 O 3 , indicating the direct contact between Fe 2 O 3 nanoparticles and MWCNT. The Fe 2 O 3 /MWCNT will enhance the transportation of charge carriers and widen the absorption spectrum [20]. Fig.4 shows the absorption spectra of Fe 2 O 3 and Fe 2 O 3 /MWCNT composite.…”