Electron transport and recombination in dye-sensitized solar cells made from single-crystal rutile TiO2 nanowires.
ABSTRACT Contrary to expectations, the electron transport rate in dye-sensitized solar cells made from single-crystal rutile titanium dioxide nanowires is found to be similar to that measured in dye-sensitized solar cells made from titanium dioxide nanoparticles.
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ABSTRACT: Nanoporous TiO2 films are commonly used as working electrodes in dye-sensitized solar cells (DSSCs). So far, there have been attempts to synthesize films with various TiO2 nanostructures to increase the power-conversion efficiency. In this work, vertically aligned rutile TiO2 nanorods were grown on fluorinated tin oxide (FTO) glass by hydrothermal synthesis, followed by deposition of an anatase TiO2 film. This new method of anatase TiO2 growth avoided the use of a seed layer that is usually required in hydrothermal synthesis of TiO2 electrodes. The dense anatase TiO2 layer was designed to behave as the electron-generating layer, while the less dense rutile nanorods acted as electron-transfer pathwaysto the FTO glass. In order to facilitate the electron transfer, the rutile phase nanorods were treated with a TiCl4 solution so that the nanorods were coated with the anatase TiO2 film after heat treatment. Compared to the electrode consisting of only rutile TiO2, the power-conversion efficiency of the rutile-anatase hybrid TiO2 electrode was found to be much higher. The total thickness of the rutile-anatase hybrid TiO2 structures were around 4.5-5.0 μm, and the highest power efficiency of the cell assembled with the structured TiO2 electrode was around 3.94%.Clean Technology. 07/2014; 20(3):306-313.
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ABSTRACT: The process of electron recombination from semiconductor (TiO2) particles to oxidized dyes in dye-sensitized solar cells is investigated theoretically. The recombination rate is evaluated using nonadiabatic electron transfer theory with system parameters computed using ab initio density functional theory (DFT) calculations and derived from experimental sources. Our model for the recombination rate includes three contributions: the semiconductor-dye coupling term (calculated by partitioning the semiconductor-dye system into the semiconductor + anchoring group and the isolated dye), the Fermi-Dirac distribution of electrons in the semiconductor’s conduction band, and the Franck–Condon term (with the reorganization energy and the driving force evaluated for the isolated dye within an implicit solvent model, and the energy of the TiO2 conduction band edge taken from experimental reports). Recombination lifetimes for several organic dyes are evaluated for a realistic range of conduction band energies. The results are in good agreement with experiment for the NKX family of dyes with a systematic variation in the dyes’ structure; however, in a second considered family of dyes, complex adsorption and conformation flexibility of the molecules make quantitative prediction of recombination times more difficult. For all considered dyes, the range of the computed recombination lifetimes is in agreement with experimental data, and the relative ordering can be reproduced for dyes with predictable adsorption chemistry.The Journal of Physical Chemistry C 03/2012; 116(14):7638–7649. · 4.84 Impact Factor
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ABSTRACT: In this paper, 4-(dicyanomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) has been used in interface modification of dye-sensitized solar cells (DSCs) with combined effects of retarding charge recombination and Förster resonant energy transfer (FRET). DCJTB interface modification significantly improved photovoltaic performance of DSCs. I-V curves shows the conversion efficiency increases from 4.27% to 5.64% with DCJTB coating. The application of DCJTB with combined effects is beneficial to explore more novel multi-functional interface modification materials to improve the performance of DSCs.Scientific Reports 07/2014; 4:5570. · 5.08 Impact Factor