Enhanced power conversion efficiency of dye-sensitized solar cells with samarium doped TiO 2 photoanodes
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In this study, TiO2 photoanodes doped with samarium ions via a method of hydrothermal treatment were used to fabricate dye-sensitized solar cells (DSSCs). Different doping concentrations were investigated on the effects of the cell’s performance. Some techniques including XRD, scanning electron microscopy, HRTEM, XPS, UV-Vis, photoluminescence were used to characterize the morphology, structure, and optic properties of the prepared photoanodes. The photovoltaic performance of the fabricated cells was further evaluated by measuring the current density–voltage (J–V) curves. It was found that: (1) The down-conversion luminescence effect derived from samarium doping could enhance the light-harvesting ability. (2) Compared with the undoped sample, the samarium-doped cells exhibited enhanced photovoltaic performance. Among the cells with different doping concentrations, the cell TiO2:0.015 Sm showed the best power conversion efficiency of 6.08% with a high open-circuit voltage (Voc) and a short-circuit current density (Jsc).
I. INTRODUCTION
With the increasing global energy demand and limited fossil resources, solar cells have been considered to be a promising renewable energy source.1 Up to now, the solar cells based on silicon are currently in the dominant position due to its high energy conversion efficiency.2 However, its application is restricted because of the high cost. Owing to the relatively low energy cost, abundant resources of raw materials, reduced negative influences on the environment, and facile production process,3–5 the dye-sensitized solar cells (DSSCs) have been attracting increasing attentions. But, the DSSCs still have some drawbacks, such as low light harvesting and high recombination rate of photogenerated electrons, restricted the dye loading capacity and utilization of the solar spectrum.6–9 To improve the DSSC’s performance, various strategies have been used, which mainly focus on the discovery of new types of light-harvesting dyes,10 fabrication of novel photoanode structures and materials,11 and synthesis of new electrolytes.12 Among various of photoanodes, titanium oxide (TiO2) was widely investigated because of its low cost and good stability.3 Nonetheless, for its wide band gap, the application of TiO2 as a photocatalyst is limited to invisible light. Up to now, many efforts have been made
Contributing Editor: Xiaobo Chen a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.357
to improve the DSSC’s performance. For example, Cui et al.13 fabricated porous TiO2 photoanodes embedded with hollow spheres, and the cell’s power conversion (5.43%) was improved due to the significant light scattering effect. In Wang et al.’s work,14 CaF2 was used to decorate the TiO2 nanocrystallite photoanodes, and the DSSC with TiO2/0.5 wt% CaF2 nanocrystallite has a maximum power conversion efficiency of 7.66%. Besides, an impressive conversion efficiency of 9.98% was also reported by incorporating TiO2 nanocrystalline photoanodes with SiO2.15 Except for incorporatin
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