Suppress the Charge Recombination in Quantum Dot Sensitized Solar Cells by Construct the Al–treated TiO₂/TiO₂ NRAs Heterojunctions

Abstract

There are many paths of recombination at the TiO 2 /CdS/ electrolyte interface. It is important to reduce the recombination rate of charges to improve the photoelectric properties of quantum dot sensitized solar cells (QDSCs). In this paper, the TiO 2 nanowire arrays (TiO 2 NRAs) has been modified with Altreated TiO 2 layer by sol-gel method to construct the Al-treated TiO 2 /TiO 2 NRAs heterojunctions. The analysis results reveal that the Fermi level of the TiO 2 has changed after being modified by Al-treated TiO 2 layer, which could form the interface electric field. The SPV, TPV and the TPC are applied to analyze the mechanism of photogenerated charge recombination. Due to the interface electric field, the SPV indicates that the separation efficiency of charge is improved; the TPV shows that the recombination of the photogenerated electrons with holes would be suppressed; and the TPC illustrates that the recombination of the photogenerated electrons with holes and electrolyte is reduced. And, the lifetime of the photo-generated electrons is prolonged. Consequently, the QDSCs based on TiO 2 NRAs photoelectrodes modified by the Al-treated TiO 2 layer exhibit a maximal solar energy conversion efficiency of 2.58 %, which is 45 % higher than that of the TiO 2 NRAs photoelectrode. Finally, our method of modifying photoanode exhibits a route to restrain the charge recombination and prolong the lifetime of photo-generated electrons, which shows a tremendous potential for the photoelectrochemical fields.[a] Dr.

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