The procedure employed for the sensitization of mesoporous photoanodes affects strongly the final performance of sensitized devices, especially when semiconductor quantum dots and quantum rods are used as sensitizers. In this work the effect of three different sensitizing methods in the final cell performance was analyzed. The TiO 2 films were sensitized with CdS QDs grown by successive ionic layer adsorption and reaction, SILAR, and with CdSe quantum rods deposited by electrophoretic and pipetting methods. Several configurations of the sensitizers and combinations of sensitization methods were tested. 4% photoconversion efficiencies were obtained for TiO 2 electrodes sensitized with CdS and CdSe by electrophoretic and pipetting respectively, while for the sensitizer with both techniques the efficiency was 4.7%. This high efficiency is mainly due to the high fill factor (60%) and the photocurrents (13.1 mA/cm 2 ) obtained by the correct combination of near-infrared and visible light photoabsorption, the better CdSe QRs distribution in the TiO 2 film and a passivation of the TiO 2 nanocrystals. Electrochemical impedance measurements has been analyzed and discussed in detail providing a detailed analysis of recombination resistance and charge transport processes. These parameters have been correlated with the cell performance.

A multilayered semiconductor sensitizer structure composed of three differently sized CdSe quantum rods (QRs), labeled as Q530, Q575, Q590, were prepared and deposited on the surface of mesoporous TiO2 nanoparticles by electrophoretic deposition (EPD) for photovoltaic applications. By varying the arrangement of layers as well as the time of EPD, the photoconversion efficiency was improved from 2.0% with the single layer of CdSe QRs (TiO2/Q590/ZnS) to 2.9% for multilayers (TiO2/Q590Q575/ZnS). The optimal EPD time was shorter for the multilayered structures. The effect of CdS quantum dots (QDs) deposited by successive ionic layer adsorption and reaction (SILAR) was also investigated. The addition of CdS QDs resulted in the enhancement of efficiency to 4.1% for the configuration (TiO2/CdS/Q590Q575/ZnS), due to increased photocurrent and photovoltage. Based on detailed structural, optical, and photoelectrical studies, the increased photocurrent is attributed to broadened light absorption while the increased voltage is due to a shift in the relevant energy levels.

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