Journal
CHEMISTRY OF MATERIALS
Volume 25, Issue 6, Pages 1000-1012Publisher
AMER CHEMICAL SOC
DOI: 10.1021/cm400220q
Keywords
sonochemical synthesis; ZnO hierarchical structure; photovoltaic; quasi-solid; dye-sensitized solar cell
Funding
- National Natural Science Foundation of China [51273032]
- National High Technology Research and Development Program for Advanced Materials of China [2009AA03Z220]
- Research Grants Council of Hong Kong [HKUST/SRFI, RPC10S C04, 603408, 604009]
- Doctoral Fund of Ministry of Education of China [20110041110003]
- Open Project Program of the State Key Laboratory of Physical Chemistry of Solid Surfaces from Xiamen University [201210]
- MCPF [SEG_H-KUST08]
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Zinc oxide (ZnO) hierarchical structures (HSs) have recently demonstrated notable photochemical and photovoltaic performances attributed to their nano/micro combined architectures. In this study, ZnO HSs were synthesized at room temperature using ultrarapid sonochemistry. This novel approach can effectively overcome deficiencies in the synthesis via traditional direct precipitation by promoting nucleation and accelerating diffusion. Only 15 min was needed to complete the formation of highly crystallized and uniformed HSs consisting of interconnected monocrystalline nanosheets using sonochemistry. The formation of HSs through in situ observations was interpreted using a new mechanism based on oriented attachment and reconstruction. In the nonequilibrium synthesis system, thicker, porous, and coarse crystallized ZnO sheets were first constructed via oriented attachment of small-sized nanocrystals. After reconstruction, untrathin, integrated, and monocrystalline nanosheets were obtained. According to the two-dimensional nanosheets to three-dimensional HSs, the formation was much more sophisticated because repeated and parallel heterogeneous oriented attachments with reconstructions dominated the final morphologies of the HSs. The relationships between synthetic conditions and HSs structures were established. Based on the photoanodes in dye-sensitized solar cells (DSCs), the performances of these differently structured HSs were tested. HSs with densely assembled nanosheets exhibited better performances in photoelectric conversions. Systematic investigations were also carried out by selecting two representative HSs to demonstrate the critical factors governing the optical and electrical properties of photoanodes. Finally, under AM 1.5 and 100mW cm(-2) light irradiation, high photoelectric conversion efficiencies of up to 6.42% were achieved. These results established a new record for quasi-solid ZnO-based DSCs.
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