Electrochemically synthesized mesoporous thin films of ZnO for highly
Igor Vasconcelos a, Anderson Lima a b, Monica Lira-Cantu b
a Universidade Federal do Ceará, Departamento de Engenharia Metalúrgica e de Materiais, Universidade Federal do Ceará, Campus do Pici Bloco 714, Fortaleza, CE 60455-760, Brazil
b Institut Catalá de Nanociência i Nanotecnologìa, Campus de la UAB, Edifici ICN2 08193 Bellaterra, Spain, Spain
International Conference on Hybrid and Organic Photovoltaics
Proceedings of 6th International Conference on Hybrid and Organic Photovoltaics (HOPV14)
Ecublens, Switzerland, 2014 May 11th - 14th
Organizers: Michael Graetzel and Mohammad Nazeeruddin
Poster, Anderson Lima, 239
Publication date: 1st March 2014

ZnO has attracted high attention due to the unique properties similar to the most applied semiconductor oxide in Dye Solar Cells (DSCs), TiO2. The advantages of ZnO in DSCs include fast charge trasnport with an electron mobility and conductivity several orders of magnitude higher to that observed for TiO2 [1,2]. Electrochemical synthesized Zinc Oxide (ZnO) permits the fabrication of novel nanostructured thin films with superior advantages like surface area, mobility, or charge transfer. In this work, nanostructured thin films of ZnO were grown on FTO sbustrates. Morphologies ranging from nanorods to mesoporous thin films were obtained by modifying the syntheis parameters. The synthesis was carried out by an electrochemical deposition process applying Zn(NO3)2.6H2O as the sole componente of the aqueos electrolyte, avoiding the use of capping agents. The composition and morphology of the prepared ZnO were characterized by EDX measurements and scanning electronic microscopy, respectively. The as deposited films were then applied as working electrodes in DSCs. The influence of the concentration of Zinc precursor in the electrolyte deposition were investigated by SEM, the amount of dye adsorbed were determined for each cell, and the performance of the cells were investigated by I-V curves and IPCE measurements. The SEM analysis showed that the morphology changes with the changes in the zinc precursor concentration. The films were electrodeposited in a bath with zinc nitrate concentrations ranging from 50 mM to 12.5 mM, and were successfully used in DSCs. The analysis of the amount of dye adsorbed reveals a decrease in power conversion efficiency of the solar cell when the amount of adsorbed dye increases.All the cells present a striking feature of this study concerns the improvement of the power conversion efficiency upon aging under ambient conditions. In terms of performance the DSCs present an open circuit voltages (Voc) varied from 0.57 V to 0.63 V, and the short circuit photocurrent desities (Jsc) ranged from 3.0 mA/cm2 to 7.6 mA/cm2, the fill factor was between 46 % and 50 %. The best cell was the cell which the mesoporous ZnO thil film was deposited in a bath containing 12.5 mM of zinc nitrate for 2h. The Voc was 0.59, the Jsc was 7.64 mA/cm2, the FF was 50.41 % and the PCE was 2.27 %. The performance of the best cell is quite good in comparison with its counterparts synthesized by the same technique and used as deposited [3,4].

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