Recomendados
Recomendados
Mais conteúdo relacionado
Mais procurados
Mais procurados (20)
Semelhante a Industrial Perspectives on Large-Area TCOs
Semelhante a Industrial Perspectives on Large-Area TCOs (20)
Mais de cdtpv
Mais de cdtpv (20)
Industrial Perspectives on Large-Area TCOs
- 2. 1 Dr. Paul D. Warren, NSG European Technical Centre - Lancashire, U.K. Industrial perspectives on large-area TCOs
- 3. 2 Outline (1) Transparent conductors – all around us! (2) Basic TCO characteristics (3) Large-area production – CVD and PVD
- 4. 3 TCOs for windows Wind Heat Loss 20 W m-2 Thermal Radiation @~10mm Conduction Radiation ‘U’ value ~>1W/m2/K (Compare ~6W/m2/K for single glazing)
- 5. TCOs for thin-film PV systems Front contact - SnO2:F Absorber Glass Back contact - metal CdTe Sheet resistance ~10-15 ohms/sq Roughness not wanted hn hn a-Si Sheet resistance ~7-10 ohms/sq Roughness necessary for light scattering
- 6. 5 Other applications for TCOs Frost-free – so you can still see the product Heat-mirror for oven Control of em signals in and out of buildings Touch-screens
- 7. 6 Outline (1) Transparent conductors – all around us! (2) Basic TCO characteristics (3) Large-area production – CVD and PVD
- 8. 7 TCO characteristics - transmission At low l – low T, high A - controlled by band-gap. At high l – low T, high R – controlled by n (Steepness of curve controlled by m) Rather unusual to have conductivity and transparency in the same material
- 9. 8 TCO characteristics ITO – ‘best’, FTO – cheapest, ZnO - intermediate ‘Best’ is defined in terms of a figure of merit – various can be chosen but all usually involve just two properties – an optical property (absorption, transmission, weighted transmission etc) and an electrical property (resistivity, conductivity). Sheet resistance 10 ohms/square, 80% visible transmission (inc. substrate) Ideal TCO – low carrier concentration (high plasma wavelength) coupled with high carrier mobility. From an industrial perspective – ease of manufacture, durability, cost
- 10. 9 TCO characteristics - morphology • Si-based systems are poor absorbers in red/NIR – so light trapping schemes necessary. • Easiest way is to use rough interfaces – layers grown on rough TCO TCO for a-Si eg NSG TECTM A7 TCO for CdTe eg NSG TECTM C15 • CdTe system – no need for light trapping schemes as very good absorber at higher wavelengths. • Interfaces can be smooth – so use smooth TCO. 10mm 0.5mm
- 11. 10 Outline (1) Transparent conductors – all around us! (2) Basic TCO characteristics (3) Large-area production – CVD and PVD
- 12. 11 Float glass manufacture - the process Batch in Furnace, 1600°C Tin bath, 1100°C Lehr, 600°C Warehouse, 20°C • ‘On-line’ TCO coating is done towards the end of the tin bath.
- 13. 12 On-line coatings CVD in tin bath Silane SiH4 Nitrogen N2 Cross section of coating head Surface of moving glass ribbon 600oC Reflective silicon coating Silicon Waste gases for treatment Si+H2 Hydrogen • What you use the glass for depends on the material – mirrors as above, TEC glass with tin oxide, Pilkington Activ self-cleaning glass with titania
- 14. 13 FTO characteristics – TEC glass Glass Buffer layer – reduce optical mismatch with subsequent layers, alter interfacial chemistry/crystallography/band structure. SnO2:F (300nm-500nm) SiO2 (25nm) SnO2 (25nm) Buffer layer Growth layers, Anti-reflection
- 15. 14 Best transparent conductor - Ag Thin (~10nm) layer of sputtered Ag grown on sputtered ZnO. Much lower absorption than other highly conducting metals Surface roughness is negligible – important for thin functional devices Absorbance of Glass/10nm Metal 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 360 410 460 510 560 610 660 710 Wavelength nm Absorbance Cu Au Al Ag
- 16. 15 Off-line coatings Magnetron sputtering • Large-scale sputter coating of glass for architectural applications
- 17. 16 Summary Large-area deposition of TCO is now an important market for flat-glass companies – windows for thermal efficiency and a whole host of up-and- coming opto-electronic applications. Optical and electrical properties important – but a large number of other considerations need to be taken into account. Significant R&D effort going into this area worldwide – and a wide range of new materials being evaluated.