Nanotechnology is enabling technologies and products at the nanoscale. It is estimated that nanotechnology will generate $4 trillion by 2015. Some key applications discussed include consumer products using silver nanoparticles, flexible solar cells using zinc oxide nanowires and carbon nanotubes, and energy storage devices like supercapacitors using nanocarbons. Research at Cambridge University is exploring new nanocomposite materials for applications in photovoltaics, lighting, batteries, and flexible electronics.

1. Nanotechnology – technology in everything Gehan Amaratunga Engineering Dept. Cambridge University

2. The scale of the physical world

3. Contact CE NANO NANO

8. Nanotechnology – some examples Photo by David Hawxhurst-Woodrow Wilson International Center for Scholars

10. Nano products – Health & Fitness Category Data courtesy Wilson of Woodrow International Centre for Scholars

14. Nanocomposites for Photovoltaic Energy Harvesting and Storage Gehan A. J. Amaratunga Electrical Engineering Division, Engineering Dept, University of Cambridge Cambridge UK ePEC Electronics, Power & Energy Conversion

17. Solar PV generation almost entirely Si cell based

18. Alternative cell technologies which are ‘cheaper’ not required for growth of solar power generation. A new Si industry growing rapidly with massive investment in new capacity

22. MWCNT NEMS Switch: Gate voltage applied to deflect suspended CNT to make contact with source. source drain gate Example of Category 1 Research at Cambridge: S.N. Cha et al, APL 2005

26. Zinc Oxide Nanowire Growth (CVD) ZnO (s) + C (s)  Zn (gas) + CO (gas) Hongjin Fan et al. Nanotechnology 17 (2006) Silicon Sapphire

27. Zinc Oxide Nanowire Characterization 2.58 Å < 001 > 01-10 0002 CNT@Cambridge Group http://www-g.eng.cam.ac.uk/cnt/

29. ZnO Nanowire Characterization

31. ZnO Nanowire Electrical Properties  = 18 - 44 Ω .cm

32. SWNT Thin Films with ZnO NWs ZnO Nanowires SWNT TF Parekh, Fanchini, Eda, Chhowalla APL 90 (2007) SWNT Network

33. ZnO NW - SWNT TF OPVs 100 mW/cm 2 Unalan et al. to be submitted Substrate

34. Use of nanostructured electrodes to have ‘area’ concentrator cells. For fixed material, target is large h but small d, l Cell 1: interpenetrated junction Cell 2: interpenetrated electrodes

35. Vertically aligned CNT – a-Si:H cell CNT a-Si:H (n-i) ITO W Fig 2. A schematic diagram showing the periodic CNT arrays offer multiple absorption opportunities in amorphous silicon photovoltaic cell.

36. a-Si:H on CNT cell Periodic CNT array a-Si: H and ITO coated CNT array

38. Fabrication sequence for CNT/a-Si:H/ITO cell I Deterministic MWCNT growth II Conformal n+ and i-a-Si:H III – ITO transparent contact IV Completed array (hole collector)

39. 500 nm MWCNT a-Si:H ITO Capacitance enhancement (i) with CNT (ii) no CNT 40 nm TEM and EDX

40. Performance of photovoltaic devices with and without CNTs arrays when illuminated with normal incident light. (b) Performance of solar cell with dot pattern CNTs electrode when illuminated with light from different incident angles

41. Wavelength dependency of I sc enhancement PV-1 PV-2 Filtered PV response PV-1 PV-2 Ⅰ Ⅱ Ⅰ Ⅱ

44. ZnO grown directly on carbon fibre

45. PV Cell

46. A room temperature processed solar cell on flexible substrate A novel ionic liquid was synthesized by grafting polyvinyl alcohol (PVA) with ionic liquid 1-butyl-3-vinylimidazolium bromide (VIC4Br) under the irradiation of a 60Co- γ source.

47. Ionic liquid based solid dye sensitised PV cell

50. Optical Properties Transmission Spectra Photoluminescense spectra 400 500 600 700 800 900 0 20 40 60 80 100 3,6 3,2 2,8 2,4 2,0 1,6 % Transmission Wavelength  (nm) Transmission spectrum -ZnO wires on ITO+glass

51. LED Fabrication Step 1: Hydrothermal Growth of ZnO nanowires on ITO coated glass Step 2: Spin coat insulating layer, dry and etch the tips No plasma 1 min 3 min 6min

53. LED structure Step 1: Hydrothermal Growth of ZnO nanowires on ITO coated glass Step 2: Spin coat insulating layer, dry and etch the tips Step 3: Spin coat organic p-type layer Step 4: Evaporate metal contact

54. LED diode Characteristic

58. Energy Storage : Two aspect are important – energy density and power density

59. Capacitive energy storage

63. Ragone plot and battery discharge curve

64. Li ion BATTERY TECHNOLOGY TRENDS ENERGY SOURCES New Lithium-based chemistries provide potential for further battery capacity improvement. A major limitation of Li ion batteries remains their loss of capacity with time irrespective of the number of charge-discharge cycles. A capacity loss of 20% per year is common.

65. A Practical solution would be an integrated device in which it appears as if a Li ion battery is connected in parallel with a supercapacitor + + - -

68. New method for bulk production of nanocarbon materials which can be suitable for energy storage applications Nature, 506 (414), 2001 Nano-onions

69. Carbon nanohorns : Bulk synthesis by arc in liquid nitrogen. Enhanced take up of metal/catalyst particles. Suitable for both Li-ion anode and Pt catalyst on electrode for fuel cells Nanotech.546(15)2004

70. Synthesis of Nanohorn-metal composite Carbon 95(42)2004

71. CNH On graphite ELECTRONICS, POWER AND ENERGY CONVERSION GROUP

72. NP agglomerates are 20-100nm diameter spherical structures with concave and convex curves inside the structure. Distance between the graphene sheets, d=0.376nm compared to ordinary graphite 0.336nm. Chemical and surface energy differences are expected because of the highly curved surface structures, and possible edge formations at the surface ELECTRONICS, POWER AND ENERGY CONVERSION GROUP

73. Surface Area Measurements of SWNHs Nitrogen adsorption isotherms taken at 77K for as-produced and modified SWNH (oxidized in air at 350 ºC). 1000 ~1500 m 2 /g ELECTRONICS, POWER AND ENERGY CONVERSION GROUP

74. Controlled MWCNT growth as basis for Supercapacitor electrodes grown single multi-wall carbon nanotube Catalyst shape Number of MWCNT  Process is very simple  High Integration density ; vertical structure  Various applications Structure effect Function part Nano capacitor Nano switch <200nm K B K Teo et al, Nanotechnology 14, 2003

77. - Electrical characteristics measurement Structure I –point MWCNTs 1um 1um Structure II-line MWCNTs 1um Ni catalyst was patterned in a dot shape (<180nm, diameter) with 1  m pitch over a 200um x 200um area. Top electrode : 220um x 320um Ni catalyst was patterned in a line shape with 180nm width, 200um length, and 1  m pitch over a distance of 200  m Top electrode : 220um x 320um

78. Capacitance Leakage current -The capacitance of the dot pattern and line pattern are about two and six times higher respectively compared to an equivalent MIM structure in same area. -This is mainly due to an increase in the effective electrode area by incorporation of vertical MWCNTs. - One MICNM structure is about 1 fF -The leakage current density is a little bit higher than in the standard MIM structure, however, this is still acceptable for many applications

82. Joint programme with Nokia to explore flexible energy storage systems