We describe a fast and effective procedure for the preparation of high efficiency hybrid photoanodes for dyesensitized solar cells (DSCs), based on nanocrystalline TiO 2 with limited addition of multiwall carbon nanotubes (CNTs). The mixing process between CNTs and TiO 2 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 TiO 2 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 TiCl 4 to boost open circuit photovoltage).

The incorporation of functionalized multi-wall carbon nanotubes into TiO2 mesoporous photoanodes for dye-sensitized solar cells leads to 30% enhancement in photoconversion efficiency of the optimized system.

h i g h l i g h t s< We studied dye sensitized solar cells with and without addition of carbon nanotubes. < CNTs can improve both photoconversion efficiency and operational stability. t r a c tWe report the improvement of the operational stability of dye-sensitized solar cells (DSSCs) by incorporating multi-wall carbon nanotubes (MWCNTs) in conventional nanostructured semiconducting TiO 2 photoanodes. DSSCs were prepared by adding various concentrations of MWCNTs (up to 1.0% wt.) to TiO 2 anatase nanoparticles. Optimization of MWCNT concentration leads to photoconversion efficiency as high as 4.1% as opposed to 3.7% for pure TiO 2 photoanodes. The performance of the solar cells was measured for 10 consecutive days of continuous ambient light exposure. MWCNT addition results in the decrease of efficiency from 4.1% to 3.7%, while a decrease from 3.7% to 2.4% was recorded in pure TiO 2 photoanodes. These results are encouraging toward the commercial exploitation of DSSCs.

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 cm2 in bare TiO2 to 17.1 mA cm2 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 photoanode

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