| 1. |
- Benetti, Daniele, et al.
(författare)
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Functionalized multi-wall carbon nanotubes/TiO2 composites as efficient photoanodes for dye sensitized solar cells
- 2016
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Ingår i: Journal of Materials Chemistry C. - 2050-7526 .- 2050-7534. ; 4:16, s. 3555-3562
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Tidskriftsartikel (refereegranskat)abstract
- We report on the effects of incorporation of different concentrations of carboxyl group (COOH)-functionalized multi-wall carbon nanotubes (F-MWCNTs) into TiO2 active layers for dye-sensitized solar cells (DSSCs). Standard DSSCs with bare TiO2 exhibit a photo-conversion efficiency (PCE) of 6.05% and a short circuit current density (Jsc) of 13.3 mA cm−2. The presence of 2 wt% F-MWCNTs in the photoanodes increases the PCE up to 7.95% and Jsc up to 17.5 mA cm−2. The photoanodes were characterized using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy. The electrochemical behaviour of the solar cells was investigated by electrochemical impedance spectroscopy (EIS). We attribute the improved performances to the combined effect of increased dye loading and reduced charge recombination (as clarified by dye loading and EIS measurements), due to the conformal coverage of F-MWCNTs, which allows fast and efficient charge collection in operating solar cells. These results can help in improving the PCE in DSSCs in an elegant and straightforward way, minimizing the need of additional steps (e.g. pre- and post-treatment with TiCl4) for photoanode preparation.
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| 2. |
- Dembele, Kadiatou Therese, et al.
(författare)
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Graphene below the percolation threshold in TiO2 for dye-sensitized solar cells
- 2015
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 3:6, s. 2580-2588
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a fast and large area-scalable methodology for the fabrication of efficient dye sensitized solar cells (DSSCs) by simple addition of graphene micro-platelets to TiO2 nanoparticulate paste (graphene concentration in the range of 0 to 1.5 wt%). Two dimensional (2D) Raman spectroscopy, scanning electron microscopy (SEM) and atomic force microscopy (AFM) confirm the presence of graphene after 500°C annealing for 30 minutes. Graphene addition increases the photocurrent density from 12.4 mA cm-2 in bare TiO2 to 17.1 mA cm-2 in an optimized photoanode (0.01 wt% graphene, much lower than those reported in previous studies), boosting the photoconversion efficiency (PCE) from 6.3 up to 8.8%. The investigation of the 2D graphene distribution showed that an optimized concentration is far below the percolation threshold, indicating that the increased PCE does not rely on the formation of an interconnected network, as inferred by prior investigations, but rather, on increased charge injection from TiO2 to the front electrode. These results give insights into the role of graphene in improving the functional properties of DSSCs and identifying a straightforward methodology for the synthesis of new photoanodes.
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| 3. |
- Dembele, Kadiatou Therese, et al.
(författare)
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Hybrid carbon nanotubes-TiO2 photoanodes for high efficiency dye-sensitized solar cells
- 2013
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Ingår i: The Journal of Physical Chemistry C. - : American Chemical Society (ACS). - 1932-7447 .- 1932-7455. ; 117:28, s. 14510-14517
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Tidskriftsartikel (refereegranskat)abstract
- We describe a fast and effective procedure for the preparation of high efficiency hybrid photoanodes for dye-sensitized solar cells (DSCs), based on nanocrystalline TiO2 with limited addition of multiwall carbon nanotubes (CNTs). The mixing process between CNTs and TiO2 nanoparticles is almost instantaneous, which makes it feasible for large-scale fabrication. Enhanced electron lifetime and reduced charge recombination lead to highly increased short circuit current density and overall photoconversion efficiency (from 13.6 mA cm-2 to 16.0 mA cm-2 and from 7.0% to 9.0%, respectively, considering the bare TiO2 and the optimum CNTs concentration, which is 0.010 wt %), while the small reduction in open circuit photovoltage does not significantly affect cell performances. This result is remarkable since a standard dye molecule (N719) was used and no chemical treatments of the photoanodes prior to cell fabrication were applied (i.e., soaking in TiCl4 to boost open circuit photovoltage). © 2013 American Chemical Society.
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