Implementation of in Process Surface Metrology for R2R Flexible PV Barrier Films
Mohamed Elrawemi*,**, Liam Blunt**, Hussam Muhamedsalih**, Feng Gao**, and Leigh Fleming**
*Mechanical Engineering Department, Elmergib University
Alkhoms, P.O.BOX 40414, Libya
**Centre for Precision Technologies, University of Huddersfield
Huddersfield, HD1 3DH, UK
Thin functional barrier layers of aluminum oxide (Al2O3) that are used particularly in photovoltaic (PV) modules to prevent the possibility of water vapor ingress should be applied over the entire PV surface without any defects. However, for barrier layer thicknesses within the sub-micrometer range (up to 50 nm) produced through the atomic layer deposition (ALD) method, it is common for defects to occur during the production process. To avoid defective barriers from being incorporated in the final PV unit, defects need to be detected during the barrier production process.
In this paper, the implementation of in process inspection system capable of detecting surface defects such as pinholes, scratches, or particles down to a lateral size of 3 µm and a vertical resolution of 10 nm over a 500 mm barrier width is presented. The system has a built-in environmental vibration compensation capability, and can monitor ALD-coated films manufactured using roll-to-roll (R2R) techniques. Ultimately, with the aid of this in process measurement system, it should be possible to monitor the coating surface process of large-area substrates, and if necessary, carry out remedial work on the process parameters.
-  A. P. Roberts, B. M. Henry, A. P. Sutton, C. R. M. Grovenor, G. A. D. Briggs, T. Miyamoto, et al., “Gas permeation in silicon-oxide/polymer (SiOx/PET) barrier films: role of the oxide lattice, nano-defects and macro-defects,” Journal of Membrane Science, Vol.208, pp. 75-88, 2002.
-  M. D. Kempe, “Control of moisture ingress into photovoltaic modules,” Photovoltaic Specialists Conference, 2005. Conference Record of the Thirty-first IEEE, pp. 503-506, 2005.
-  S. M. George, “Atomic layer deposition: an overview,” Chemical Reviews, Vol.110, pp. 111-131, 2009.
-  M. Elrawemi, L. Blunt, L. Fleming, and F. Sweeney, “Further development of surface metrology methods for predicting the functional performance of flexible photovoltaic barrier films,” Surface Topography: Metrology and Properties, Vol.1, p. 015006, 2013.
-  L. Blunt, M. Elrawemi, L. Fleming, and F. Sweeney, “Correlation of micro and nano-scale defects with WVTR for aluminium oxide barrier coatings for flexible photovoltaic modules,” IJPTECH, Vol.3, pp. 290-302, 2013.
-  M. Wegner, “Greater Automation of Testing Will Help Flexible and Rigid Electronic Manufacturers Improve Product Quality and Decrease Costs,” 2014, available at: http://smttoday.com/ [accessed March 19, 2015]
-  M. George, “Design and Development of a State of the Art R2R Production Platform For Flexible Transparent Barrier Films,” presented at the Web Coating & Handling Conference, South Carolina 2014.
-  X. Jiang, K. Wang, F. Gao, and H. Muhamedsalih, “Fast surface measurement using wavelength scanning interferometry with compensation of environmental noise,” Applied optics, Vol.49, pp. 2903-2909, 2010.
-  H. Muhamedsalih, X. Jiang, and F. Gao, “Accelerated surface measurement using wavelength scanning interferometer with compensation of environmental noise,” Procedia CIRP, Vol.10, pp. 70-76, 2013.
-  H. Muhamedsalih, “Investigation of Wavelength Scanning Interferometry for Embedded Metrology,” PhD Doctoral dissertation, University of Huddersfield, Huddersfield 2013.
-  W. Kaplonek and C. Lukianowicz, “Coherence correlation interferometry in surface topography measurements,” Recent Interferometry Applications in Topography and Astronomy, I. Padron, Ed., ed: InTech, pp. 1-26, 2012.
-  ISO25178-2, “Geometrical product specifications (GPS) – Surface texture: Areal – Part 2: Terms, definitions and surface texture parameters,” 2012.
-  M. Elrawemi, L. Blunt, L. Fleming, D. Bird, D. Robbins, and F. Sweeney, “Modelling water vapour permeability through atomic layer deposition coated photovoltaic barrier defects,” Thin Solid Films, Vol.570, Part A, pp. 101-106, 2014.
-  L. Blunt and S. Xiao, “The use of surface segmentation methods to characterise laser zone surface structure on hard disc drives,” Wear, Vol.271, pp. 604-609, 2011.