Abstract
Vertically aligned ZnO/TiO2(VA-ZnO/TiO2) core-shell composites deposited on ZnO-seeded indium tin oxide (ITO) glasses have been synthesized by a chemical bath deposition approach for growing one-dimensional ZnO structure followed by a spin procedure for coating TiO2on the surface of ZnO structure. The influences of the cycles of spin coating of TiO2(CSCT) on the properties of VA-ZnO/TiO2and performances of the assembled DSSCs were studied. The power conversion efficiency of the VA-ZnO/TiO2-based DSSC measured under illumination of 100 mW/cm2and AM 1.5 can reach 0.81%, representing 93% improvement when compared with that of the pristine VA-ZnO electrode (0.42%). The intensity-modulated photocurrent spectroscopy (IMPS) and electrochemical impedance spectroscopy (EIS) were applied to study the kinetics and interfacial transfer of the photogenerated electrons. Both the photocurrent and power conversion efficiency correlate well with the steady state electron density. Enlargement in surface area and dye adsorption, suppression of dissolution of Zn2+, diminishment in electron recombination, and fast transfer of injected electrons from excited dyes to TiO2conduction bands arising from coating TiO2on VA-ZnO are regarded as the predominant causes for this improvement.
Highlights
Regarded as a promising alternative to conventional siliconbased solar cells, DSSCs have attracted worldwide attention in both academia and industry because of the inherent characteristics of low production cost, simple processing, less toxic manufacturing, and moderate energy conversion efficiency [1,2,3,4,5]
We presented a simpler spin coating method to obtain a shell layer of TiO2 coated on Vertically aligned (VA)-ZnO arrays, which acted as photoanodes assembled in DSSCs in an attempt to improve photovoltaic performance by combining the advantages of high surface area and chemical inertness of TiO2 and high electron transport rate of 1D ZnO nanostructures
The prepared samples were denoted as ZaTb, where a and b represented the cycles of chemical bath deposition of ZnO (CCBDZ) and spin coating of TiO2 (CSCT), respectively
Summary
Regarded as a promising alternative to conventional siliconbased solar cells, DSSCs have attracted worldwide attention in both academia and industry because of the inherent characteristics of low production cost, simple processing, less toxic manufacturing, and moderate energy conversion efficiency [1,2,3,4,5]. The electron diffusion coefficient and electron mobility of ZnO film are reported to be 1.2 × 10−4 cm2/s and 10−1–10−3 cm V−1 s−1, which are both higher than those of 5 × 10−5 cm2/s and 10−6–10−4 cm V−1 s−1, respectively, of TiO2 [12,13,14,15,16,17,18] These characteristics imply that ZnO can be a potential candidate as the photoanode of DSSC in addition to TiO2 semiconductor [3]. We presented a simpler spin coating method to obtain a shell layer of TiO2 coated on VA-ZnO arrays, which acted as photoanodes assembled in DSSCs in an attempt to improve photovoltaic performance by combining the advantages of high surface area and chemical inertness of TiO2 and high electron transport rate of 1D ZnO nanostructures. The properties of the prepared VA-ZnO/TiO2 structures and their influences on the performance of the DSSCs were investigated
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