Zinc oxide (ZnO) nanostructures with various morphologies (pencil-like nanorods, nanotubes, and lotus-like structures) have been successfully formed by simple oxidation of vacuum deposited Zn thin film on glass/ITO substrates in hot water at 90 °C. The morphology evolved from pencil-like nanorods to nanotubes to lotus-like structures with prolonged oxidation of Zn thin film for 6–24 h. The change in morphology of ZnO is attributed to the combined effects of electrochemical reactions in the solution, morphology and structure of Zn thin film, and wurtzite structure of resulting ZnO. A hybrid organic–inorganic solar cell following an inverted bulk heterojunction configuration was fabricated based on the lotus-like ZnO structures. The solar cell achieved a power conversion efficiency of up to 1.18%, which demonstrates the applicability of the technique for photovoltaic applications.
Zinc oxide Wet oxidation Hot water Hybrid solar cell Nanostructures
This study was funded by the Department of Science and Technology under the Engineering Research and Development for Technology and the College of Engineering, University of the Philippines under the Faculty Research Incentive Award and Green Photonics Project of Nara Institute of Science and Technology.
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Conflict of interest
The authors declare that they have no conflict of interest.
Arshad, M.: Band gap engineering and enhanced photoluminescence of Mg doped ZnO nanoparticles synthesized by wet chemical route. J. Lumin. 161, 275–280 (2015)CrossRefGoogle Scholar
Balela, M.D.L.: In situ mixed potential study of the growth of zinc oxide hierarchical nanostructures by wet oxidation of zinc foil. J. Mater. Sci. 52, 2319–2328 (2017)ADSCrossRefGoogle Scholar
Fan, F.: Facile synthesis and gas sensing properties of tubular hierarchical ZnO self-assembled porous nanosheets. Sens. Actuators, B 215, 231–240 (2015)CrossRefGoogle Scholar
Gu, C.: Preparation of porous flower-like ZnO nanostructures and their gas-sensing property. J. Alloy. Compd. 509, 4499–4504 (2011)CrossRefGoogle Scholar
Huang, J.: Facile synthesis of porous ZnO nanowires consisting of ordered nanocrystallites and their enhanced gas-sensing property. Sens. Actuators, B 188, 249–256 (2013)CrossRefGoogle Scholar
Huang, Y.: Fabrication and characterization of ZnO comb-like nanostructures. Ceram. Int. 32, 561–566 (2006)CrossRefGoogle Scholar
Huang, Y.: Low-temperature and two-step evaporation growth of ZnO nanotetrapods and their field emission properties. Mater. Lett. 62, 1342–1344 (2008)CrossRefGoogle Scholar
Liu, W.C., Cai, W.: Synthesis and characterization of ZnO nanorings with ZnO nanowires array aligned at the inner surface without catalyst. J. Cryst. Growth 310, 843–846 (2008)ADSCrossRefGoogle Scholar
Liu, Y., Gao, W.: Growth process, crystal size and alignment of ZnO nanorods synthesized under neutral and acid conditions. J. Alloy. Compd. 629, 84–91 (2015)CrossRefGoogle Scholar
Park, J.Y.: Formation of networked ZnO nanowires by vapor phase growth and their sensing properties with respect to CO. Mater. Lett. 65, 2755–2757 (2011)CrossRefGoogle Scholar
Pelicano, C.M.: Zinc oxide nanostructures formed by wet oxidation of zinc foil. Adv. Mater. Res. 1043, 22–26 (2014)CrossRefGoogle Scholar
Qu, X.: Preparation and optical property of porous ZnO nanobelts. Mater. Sci. Semicond. Process. 15, 244–250 (2012)CrossRefGoogle Scholar
Roza, L.: Direct growth of oriented ZnO nanotubes by self-selective etching at lower temperature for photo-electrochemical (PEC) solar cell application. J. Alloy. Compd. 618, 153–158 (2015)CrossRefGoogle Scholar
Ruankham, P.: Surface modification of ZnO nanorods with small organic molecular dyes for polymer-inorganic hybrid solar cells. J. Phys. Chem. C 115, 23809–23816 (2011)CrossRefGoogle Scholar
Skeerantan, S.: Room temperature anodic deposition and shape control of one-dimensional nanostructured zinc oxide. J. Alloys Comp. 476, 513–518 (2011)Google Scholar
Tan, W.K.: Formation of highly crystallized ZnO nanostructures by hot-water treatment of etched Zn foils. Mater. Lett. 91, 111–114 (2013a)CrossRefGoogle Scholar
Tan, W.K.: Optical properties of two-dimensional ZnO nanosheets formed by hot-water treatment of Zn foils. Solid State Commun. 162, 43–47 (2013b)ADSCrossRefGoogle Scholar
Tan, W.K.: Synthesis of ZnO nanorod-nanosheet composite via facile hydrothermal method and their photocatalytic activities under visible light irradiation. J. Solid State Chem. 211, 146–153 (2014)ADSCrossRefGoogle Scholar