Abstract
Large area rutile TiO2 nanorod arrays were grown on F:SnO2 (FTO) conductive glass using a hydrothermal method at low temperature. CdSe quantum dots (QDs) were deposited onto single‐crystalline TiO2 nanorod arrays by a chemical bath deposition (CBD) method to make a photoelectrode. The solar cell was assembled using a CdSe‐TiO2 nanostructure as the photoanode and polysulfide solution as the electrolyte. The annealing effect on optical and photovoltaic properties of CdSe quantum‐dots‐sensitized TiO2 nanorod solar cells was studied systematically. A significant change of the morphology and a regular red shift of band gap of CdSe nanoparticles were observed after annealing treatment. At the same time, an improved photovoltaic performance was obtained for quantum‐dots‐sensitized solar cell using the annealed CdSe‐TiO2 nanostructure electrode. The power conversion efficiency improved from 0.59% to 1.45% as a consequence of the annealing effect. This improvement can be explained by considering the changes in the morphology, the crystalline quality, and the optical properties caused by annealing treatment.
Highlights
IntroductionTechnologies to utilize solar energy have attracted world-wide attention
At present, technologies to utilize solar energy have attracted world-wide attention
Field emission scanning electron microscopy (FESEM) images show a typical morphology of the rutile TiO2 nanorod arrays in Figure 1(a), confirming that the entire surface of the fluorine-doped tin oxide (FTO)-coated glass substrate was uniformly covered with ordered TiO2 nanorods
Summary
Technologies to utilize solar energy have attracted world-wide attention. Considering the high cost and low stability of organic dyes, using nanosized narrowband gap semiconductor materials as sensitizers in place of the molecular dyes in DSSCs has been put forward as an efficient and promising alternative. The use of CdSe quantum dots, which may produce more than one electron-hole pair per single absorbed photon ( known as multiple exciton generation (MEG)), is a promising solution to enhance power conversion efficiency. The creation of a type-II heterojunction by growing CdSe QDs on the TiO2 surface greatly enhances charge separation All these effects are known to increase the exciton concentration, quantum yield, and lifetime of hot electrons and the performance of QD-sensitized solar cells. We combine CdSe semiconductor quantum dots and single-crystalline rutile TiO2 nanorod arrays to produce a practical quantum-dot-sensitized solar cell. The photoconversion efficiency of the quantum-dots-sensitized solar cell assembled using a CdSe-TiO2 nanostructure annealed at 400◦C for 30 min showed an increase of 146% compared with that based on as-grown CdSe-TiO2 nanostructure
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