Here we analyze the effect of two relevant aspects related to cell preparation on quantum dot sensitized solar cells (QDSCs) performance: the architecture of the TiO2 nanostructured electrode and the growth method of quantum dots (QD). Particular attention is given to the effect on the photovoltage, Voc, since this parameter conveys the main current limitation of QDSCs. We have analyzed electrodes directly sensitized with CdSe QDs grown by chemical bath deposition (CBD) and successive ionic layer adsorption and reaction (SILAR). We have carried out a systematic study comprising structural, optical, photophysical and photoelectrochemical characterization in order to correlate the material properties of the photoanodes with the functional performance of the manufactured QDSCs. The results show that the correspondence between photovoltaic conversion efficiency and the surface area of TiO2 depends on the QDs deposition method. Higher Voc values are systematically obtained for TiO2 morphologies with decreasing surface area and for cells using CBD growth method. This is systematically correlated to a higher recombination resistance of CBD sensitized electrodes. Electron injection kinetics from QDs into TiO2 also depends on both the TiO2 structure and the QDs deposition method, being systematically faster for CBD. Only for electrodes prepared with small TiO2 nanoparticles SILAR method presents better performance than CBD, indicating that the small pore size disturb the CBD growth method. These results have important implications for the optimization of QDSCs.

This work was partially supported by the Ministerio de Educación y Ciencia of Spain under the project HOPE CSD2007-00007 (Consolider-Ingenio 2010) JES-NANOSOLAR PLE2009-0042, MAT 2010-19827, MAT2011-23593 and the Ramon y Cajal program, by Junta de Andalucía for grants FQM3579 and FQM5247 and by Generalitat Valenciana under project PROMETEO/2009/058. Q. Shen would like to thank PRESTO program, Japan Science and Technology Agency (JST) for supporting part of this work. The SCIC of UJI are acknowledged for its help in BET, SEM and TEM measurements.

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