Thin-Film Technology on Flat Glass and Applications Part II - Chapter 5 Transparent, electrically conducting coatings and products with which they are manufactured - Chapter 6 Flat glass products with electrically controllable functions - Chapter 7 Photovoltaic modules on the basis of thin-film solar cells onto flat glass - Appendix Admittance calculations for determining the opti- cal values of coated glass Definition of colour and colour rendering All rights reserved. Reproduction of the whole or parts of this book for any purpose with- out explicit permission by the author is prohibited. Glass goblet with a decorative enamel coating with the name of Pharaoh Thutmosis III in the cartouche (from about 1450 B.C.) Soon after the invention of glass as a material, artisans learned how to refine it by coating. 3 Page Table of Contents………………………………………………………….…………… 3 Foreword……………………………………………………………………… 5 5 Flat glass products with thin film coatings…………………………….. 6 5.1 Transparent conductive coatings (TCO)……………………………………………. 7 5.1.1 Technical terms and physical foundations ………………………………………… 7 5.1.1.1 Electrical conductivity and low thermal emissivity………………………………….16 5.1.1.2 Electrical conductivity and high transmission of light and solar radiation………. 21 5.1.2 Industrially applied coatings…………………………………………………………. 32 5.1.2.1 Transparent conductive coatings on the basis of semiconductors……………….32 5.1.2.2 Transparent conductive coatings on the basis of metals…………………………. 45 5.1.3 Flat glass products with transparent, electrically conductive coatings …………. 61 5.1.3.1 Thermally insulating glazing with low-emissivity coatings………………………... 62 5.1.3.2 Glazing with low-emissivity coatings on the outdoor and indoor surfaces…….. 74 5.1.3.3 Shielding glazing for electromagnetic radiation…………………………………….105 5.1.3.4 Glazing with attenuation of the radar echo ………………………………………… 112 5.1.3.5 Anti-static glazing …………………………………………………………………….. 117 5.1.3.6 Heatable glazing………………………………………………………………………..119 5.1.3.7 Transparent switches (touch panels, touch screens)…………………………….. 122 5.1.3.8 Transparent electrodes………………………………………………………………. 126 5.1.3.9 Contacting of conductive glass………………………………………………………. 128 5.2 Solar control glazing………………………………………………………………….. 131 5.3 Anti-reflection coatings on flat glass surfaces and their application…………….. 145 5.3.1 Anti-reflection based on destructive interference…………………………………..147 5.3.2 Anti-reflection based on fine surface roughening ………………………………….156 5.4 Mirror coatings and their applications………………………………………………..160 5.4.1 Mirror coatings based on metallic layers…………………………………………… 160 5.4.2 Mirror coatings based on dielectric layers………………………………………….. 165 5.4.3 Coatings which influence the surface energy (hydrophilic and hydrophobic coatings) and their applications……………………………………………………… 170 5.5.1 Terminology and physical and chemical basics…………………………………… 170 5.5.2 Coatings which influencing the surface energy and their application…………… 177 5.6 Criteria and test procedures to characterise the durability of coatings on flat glass………………………………………………………………………………………… .185 6 Products with electrically controllable functions based on coated flat glass………………………………………………………………………………. 191 6.1 Optoelectronic displays using coated flat glass …………………………………… 191 6.1.1 Liquid crystal displays………………………………………………………………… 191 4 6.2 Glass panes with electrically controllable spectral transmittance or reflectance……………………………………………………………………………... 199 6.2.1 Panes with electrically controllable light transmittance based on liquid crystals………………………………………………………………………….. 199 6.2.2 Panes with controllable transmittance based on electrochromy ………………… 204 7 Photovoltaic modules based on thin-film solar cells on flat glass 7.1 Definition and market importance of solar cells…………………………………… 220 7.2 Structure and function of solar cells………………………………………………… 222 7.3 Today’s marketed thin-film solar cells ……………………………………………… 223 7.4 Design of a photovoltaic module with thin film solar cells………………………… 228 7.5 Applications of photovoltaic modules………………………………………………. 229 7.6 Flat glass panes for the application with photovoltaic modules………………….. 230 Appendix AI. Calculating the spectral behaviour of layer systems in the range of of solar radiation by means of the admittance method……………….…………... 232 AII. Calculating the spectral properties of conductive layers in the range of large wavelengths………………………………………………………….. 243 AIII. Colour and colour rendering…………………………………………………………. 246 List of references …………………………………………………………………………248 5 Foreword This E-book is based on the English manuscript, „Large-Area Glass Coating“, which was the basis for translation and publication of a book of the same title in Chinese by the Ardenne Anlagentechnik company in Dresden, Germany. It was improved in various places and brought up to date (2015) by the author as far as possible. The author thanks the Interpane AG company and employees of the Interpane Entwicklungs- und Beratungsgesellschaft mbH company in Lauenförde, Germany, particularly Dr Lothar Herlitze and Kerstin Sorby, for financial support and expert assistance in preparing this E-book, as well as Dr Helen Rose Wilson from the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg, Germany, for the committed help to translate the German text into English. My thanks also go to my daughter, Stephanie Sahl, for designing the cover. Hans Joachim Gläser Gummersbach, October 2016 6 5 Flat glass products with thin film coatings Flat glass coated with thin films is of considerable economic importance. These coatings on flat glass predominantly fulfil the following functions: - Low emissivity for thermal radiation - Electrical conduction - Antireflection - Reflection - Decorative effects As will be shown in this chapter, there are some physical interrelations between these functions. The physical phenomena of electrical conduction and interference of electro- magnetic waves serve as the foundations of all the functions mentioned above. Interfer- ence arises when two or more waves (in this case solar or thermal radiation, radar, TV or radio waves) are superimposed with the result that they are either amplified or weakened. The flat glass products with thin films currently on the market are basically - Thermally insulating glazing used in the construction industry to lower energy con- sumption in heating and air-conditioning systems - Solar-control glazing also used in the construction industry for decorative and energy- saving effects - Antireflective glass used externally and internally in construction, but primarily as the front glass layer for modern liquid crystal displays or glazing for solar energy convert- ers - Mirrors used for interior decoration, fashion accessories, in bathrooms and in vehicles - Conductive glass as a component for a growing number of flat glass products with switchable properties, such as liquid crystal displays or electrochromic or electrotropic glazing All thin film coatings deposited on flat glass on an industrial scale today make use of at least two of the functions mentioned above. For example, - Thermally insulating coatings - the low thermal emissivity and antireflective properties - Solar-control coatings - the low thermal emissivity, reflective properties and decora- tive effects - Conductive coatings - the conductive and antireflective properties - Mirrors - reflective properties and decorative effects Thus the layer systems coated using thin film technologies fulfil multiple functions (see Chapter 2 in Part I). For an increasing number of flat glass products, thin film and thick film coatings are combined, e.g. to manufacture spandrel panels for the construction in- dustry, mirrors, panes with variable solar transmittance, photovoltaic modules and plasma displays. 7 The range of functions added to flat glass has been further extended. Flat glass with hydrophobic, hydrophilic, photocatalytic, anti-soiling, surface-hardening or solar-energy converting properties or with variable solar transmittance are commercially available today, again, usually in combination with functions that are already available. The applications of flat glass are improved and their num- ber extended, such that the flat glass market has not only been strengthened, but is also expanding further. 5.1 Transparent conductive coatings (TCC) Transparent, electrically conductive coatings on flat glass can perform a large number of functions. Most industrially produced flat glass products using thin film coatings are based on transparent conductive coatings. As a result, these have greater economic importance than all other thin films used today. All the functions achieved with transparent conductive coatings are based on the effects of the free electrons in these layers. Their significant distinguishing feature is whether the functions are based on conduction by the free electrons in the layers or on their interaction with electromagnetic radiation. The former effect is explained by OHM’s Law, which states that an electric current flows within the layers when a voltage is applied. The latter effect mainly influences reflection in the spectral range from solar radiation to the long waves of radio transmission, which is caused by the interaction of the incident radiation with free electrons in the layers. Apart from the physical effects based on the properties of the free electrons, modern transparent conductive coatings employed industrially make use of reflection or antireflec- tive effects in the wavelength range mentioned above which