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Strategies for the Design and Fabrication of Improved Transparent
Conducting Oxide Thin Films via the use of In-situ Growth Monitoring
and the Exploitation of Photonic Band Gap Materials
Martyn E. Pemble1, Justin C Costello1, Ian M Povey1, Dimitra Vernardou2* and David W Sheel2
1Tyndall National Institute, University College Cork, Lee Maltings, Prospect Row, Cork, Ireland
Email: mailto:[email protected]
2Institute for Materials Research, University of Salford, Salford, M5 4WT, UK
* present address, to be added
For a photovoltaic device based on an already optimised active photo absorber medium it is
arguable that improvements in device efficiency can only be made via the optimisation of the
associated components of the device. One such component is the transparent conducting oxide
(TCO) that is used to provide electrical conductivity through the device and to permit the passage
of light into the absorbing medium. Chemical vapour deposition (CVD) is a useful method for the
production of such TCO layers since it is a relatively fast and cheap process, while varying the
parameters employed often allows one to tune film morphology and in some case crystallinity. As
such it is apparent that understanding how these CVD processes actually work could provide the
means of optimising the growth and properties of the resulting TCO films. In the first part of this
presentation results for the use of IR spectroscopic methods for the study of the growth of SnO2
films on glass will be presented. It will be demonstrated that near-IR diode laser spectroscopy is a
powerful method for the study of such reactions as illustrated for the precursor system SnCl4 and
H2O. In addition, broad band FTIR spectroscopy has been used to study the growth of SnO2 from
the alternative precursor combination (CH3)2SnCl2 and O2.
Although not strictly relevant to the discussion of TCO materials, additional data will then be
presented for the growth of the novel thermochromic material VO2 from both VCl4/H2O and
vanadyl acetoacetonate (VO(acac)2), since we have also performed detailed spectroscopic studies
of these growth systems using FTIR methods. These data are used to illustrate the methodology
whereby individual reacting species may be identified and correlated within an otherwise
complex system.
Finally, reference will be made to the emerging field of the use of photonic band gap (PBG)
materials to produce improved photovoltaic systems. We present data for the growth of doped
ZnO inside photonic band gap materials based on synthetic opals, which are synthesised and
assembled in our laboratories. We demonstrate that under the correct conditions of PBG
fabrication and modification of the photonic stop band by careful choice of infill levels, it is
possible to design a material where the passage of photons through the film is significantly
enhanced as compared to a non PBG system.

Source: http://www.iesl.forth.gr/conferences/tco2006/downloads/abstracts/pemble.pdf