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Hydrothermal growth of ZnO nanorods for solar cells applications

Bartłomiej S. Witkowski 1Łukasz Wachnicki 1Rafał Pietruszka 1Sylwia Gierałtowska 1Grzegorz Łuka 1Marek Godlewski 1,2

1. Institute of Physics, Polish Academy of Sciences, Warsaw 02-668, Poland
2. Cardinal Stefan Wyszynski University, College of Science, Deptartment of Mathematics and Natural Sciences, Warszawa, Poland


Zinc oxide is a II-VI semiconductor material that focused a growing interest in various fields such as biology, medicine or electronics. It has a direct energy gap of about 3,37eV at room temperature and high transparency in a visible light spectral region. This semiconductor reveals very special physical and chemical properties, which imply many applications including a active layer or transparent electrode in solar cells or LED diodes. ZnO is also tested for applications in new generations of electronic devices as an active part of transparent transistors and cross-bar memories.

Among many applications, ZnO is also a prospective material for PV and sensor technologies, where developed surface morphology is very important. In this work we present growth of ZnO nano-columns using a new approach to the hydro-thermal method.

We used p-type silicon as a substrate with a thin gold layer (1nm) on the surface. ZnO nanostructures were grown from the water solution at extremely low temperature of 50°C. We used deionized water and zinc acetate as an oxygen and zinc precursors, respectively. The gold on the surface nucleates growth of the ZnO nanorods. In reaction we used a mixture consisting of water, zinc acetate and sodium hydroxide, which act as a pH regulator.  

The method is characterized by extremely high growth rate (it takes only few minutes) and  simple solution. It allows to regulate orientation and sizes of the ZnO nanorods in a large extent. Due to simplicity and safety of this method, it is suitable for industrial applications. Low costs relate also to the fact that our approach does not require a vacuum, high temperature, pressure, or hazardous chemicals.

In this work we present the properties of nanorods grown using hydro-thermal method for photovoltaic applications. On the nanorods grown on p-type Si we deposited a layer of ZnO:Al as a transparent electrodes using Atomic Layer Deposition method. Thrimetylaluminium was used as aluminum precursor to dope zinc oxide layer. Ohmic contacts to p-Si were deposited by e-beam evaporation. The obtained PV heterostructure, Au/Si/ZnONR/ZnO:Al showed a clear photovoltaic response. Current-voltage characteristic at 100mW/cm2 illumination conditions will be presented. The details of the ZnO nanorods growth using hydro-thermal method and photovoltaic response will be discussed.

The research was partially supported by the European Union within European Regional Development Fund  through grant Innovative Economy (POIG. 01.01.02-00-108/09).


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Related papers

Presentation: Oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, Topical Session 3, by Bartłomiej S. Witkowski
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-03-27 13:15
Revised:   2013-03-27 13:32