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Silicon Nanowire based Solar Cells

Silicon Nanowire based Solar Cells. International Congress On Renewable Energy ICORE 2010 2 nd December, 2010. Pragya Singh Pratul K Singh. Silicon Nanowire based Solar Cells. Outline: Light Trapping in Cells Solar Cell Energy Conversion in Solar Cell Solar Cells Everywhere

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Silicon Nanowire based Solar Cells

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  1. Silicon Nanowire based Solar Cells International Congress On Renewable Energy ICORE 2010 2nd December, 2010. Pragya Singh Pratul K Singh

  2. Silicon Nanowire based Solar Cells • Outline: • Light Trapping in Cells • Solar Cell • Energy Conversion in Solar Cell • Solar Cells Everywhere • Planar Silicon Solar Cell • Nanowires- Properties • Silicon Nanowires- Properties • Fabrication • Techniques for SiNW Deposition • Experiment at the SSN Research Centre ICORE - 2010, Pragya Singh, Pratul K Singh

  3. Silicon Nanowire based Solar Cells • Outline: • Light Trapping in Cells • Solar Cell • Energy Conversion in Solar Cell • Solar Cells Everywhere • Planar Silicon Solar Cell • Nanowires- Properties • Silicon Nanowires- Properties • Fabrication • Techniques for SiNW Deposition • Experiment at the SSN Research Centre ICORE - 2010, Pragya Singh, Pratul K Singh

  4. Light Trapping in Cells: Sun already provides all the energy needed to support life. So the Challenge? ICORE - 2010, Pragya Singh, Pratul K Singh

  5. Light Trapping in Cells: • One to One conversion: • Blue photon = 2 times more energy than the Red Photon • Both produce 1 electron each. • Effective light energy utilized? ICORE - 2010, Pragya Singh, Pratul K Singh

  6. Silicon Nanowire based Solar Cells • Outline: • Light Trapping in Cells • Solar Cell • Energy Conversion in Solar Cell • Solar Cells Everywhere • Planar Silicon Solar Cell • Nanowires- Properties • Silicon Nanowires- Properties • Fabrication • Techniques for SiNW Deposition • Experiment at the SSN Research Centre ICORE - 2010, Pragya Singh, Pratul K Singh

  7. Solar Cell • Cell is thin Si wafer • Size 10x10 cm : size of a CD • Thickness is in fractions of mm • Metal pattern is to make electrical contacts. ICORE - 2010, Pragya Singh, Pratul K Singh

  8. Silicon Nanowire based Solar Cells • Outline: • Light Trapping in Cells • Solar Cell • Energy Conversion in Solar Cell • Solar Cells Everywhere • Planar Silicon Solar Cell • Nanowires- Properties • Silicon Nanowires- Properties • Fabrication • Techniques for SiNW Deposition • Experiment at the SSN Research Centre ICORE - 2010, Pragya Singh, Pratul K Singh

  9. Energy Conversion in Solar Cell • Light is shone • Electrons are knocked out • Electrons and holes move in opposite directions • Electrical output is generated between the contacts. ICORE - 2010, Pragya Singh, Pratul K Singh

  10. Silicon Nanowire based Solar Cells • Outline: • Light Trapping in Cells • Solar Cell • Energy Conversion in Solar Cell • Solar Cells Everywhere • Planar Silicon Solar Cell • Nanowires- Properties • Silicon Nanowires- Properties • Fabrication • Techniques for SiNW Deposition • Experiment at the SSN Research Centre ICORE - 2010, Pragya Singh, Pratul K Singh

  11. Solar Cells Everywhere Solar cells : • Safe • Clean • Quiet • Durable • Reliable • Installable anywhere ICORE - 2010, Pragya Singh, Pratul K Singh

  12. The Main Catch • Material Cost • Thickness of material • Purity • Fabrication Cost ICORE - 2010, Pragya Singh, Pratul K Singh

  13. Silicon Nanowire based Solar Cells • Outline: • Light Trapping in Cells • Solar Cell • Energy Conversion in Solar Cell • Solar Cells Everywhere • Planar Silicon Solar Cell • Nanowires- Properties • Silicon Nanowires- Properties • Fabrication • Techniques for SiNW Deposition • Experiment at the SSN Research Centre ICORE - 2010, Pragya Singh, Pratul K Singh

  14. Planar Silicon Solar Cells: • Thickness for an efficient light absorption • High purity to avoid recombining • High Reflectance • High Recombination Rate. ICORE - 2010, Pragya Singh, Pratul K Singh

  15. Sliced into Nano-scale • Diameters from 1 to 50nm • Nano scale Silicon has a color difference • Quantum Confinement • Nano sized Silicon shows: • Physical • Optical • Electronics properties change • Electrons occupy different energy levels ICORE - 2010, Pragya Singh, Pratul K Singh

  16. Conductance can be Improved Bulk Silicon atom: Tetravalent Tend to achieve Stability Bond with 4 other atoms Silicon Nanowire: Tetravalent Tend to achieve stability Cling with atmospheric Oxygen Silica is formed ICORE - 2010, Pragya Singh, Pratul K Singh

  17. Conductance can be Improved Prevention of Silica: Conductivity increases 10 times Prevention at high temperatures – 700C High Vaccum ICORE - 2010, Pragya Singh, Pratul K Singh

  18. Silicon Nanowire based Solar Cells • Outline: • Light Trapping in Cells • Solar Cell • Energy Conversion in Solar Cell • Solar Cells Everywhere • Planar Silicon Solar Cell • Nanowires- Properties • Silicon Nanowires- Properties • Fabrication • Techniques for SiNW Deposition • Experiment at the SSN Research Centre ICORE - 2010, Pragya Singh, Pratul K Singh

  19. Nanowires- Properties • No Lattice Mismatch. • Flexibility to create heterostructures. • Broad range of materials. • Integration of compound semiconductor based optoelectronic devices with silicon based microelectronics. ICORE - 2010, Pragya Singh, Pratul K Singh

  20. Silicon Nanowire based Solar Cells • Outline: • Light Trapping in Cells • Solar Cell • Energy Conversion in Solar Cell • Solar Cells Everywhere • Planar Silicon Solar Cell • Nanowires- Properties • Silicon Nanowires- Properties • Fabrication • Techniques for SiNW Deposition • Experiment at the SSN Research Centre ICORE - 2010, Pragya Singh, Pratul K Singh

  21. Silicon Nanowires- Properties Recombination: • Poor efficiency may be due to recombination within the bulk silicon element. • Photon strikes the p-n junction in bulk silicon, Produces an electron-hole pair. • Electron and hole must travel along the wire to produce current. ICORE - 2010, Pragya Singh, Pratul K Singh

  22. Silicon Nanowires- Properties Recombination: Tendency to recombine with other oppositely charged charge carrier Resulting in heat generation rather than electrical energy ICORE - 2010, Pragya Singh, Pratul K Singh

  23. Silicon Nanowires- Properties Reduced Recombination in SiNW: • Small diameters. • SiNWsgrown vertical, perpendicular to the surface of the substrate. • Electrons strikes on the surface. • Distance of hole/electron travel is minimized. • Distance is of the order of nanometers. ICORE - 2010, Pragya Singh, Pratul K Singh

  24. Silicon Nanowires- Properties Light Trapping: Light falling on the substrate gets reflected and once again gets absorbed by silicon nanowires. ICORE - 2010, Pragya Singh, Pratul K Singh

  25. Silicon Nanowires- Properties Increased Surface Area: • Very narrow pointed structures. • Diameter in nanometers. • Length in micrometers. • Greater area made of p-n junctions is exposed to sunlight. • Increases absorptivity. ICORE - 2010, Pragya Singh, Pratul K Singh

  26. Silicon Nanowires- Properties • Reduced size • Increased absorptivity • Reduced reflectivity • Efficient electron transport • Reduced Recombination ICORE - 2010, Pragya Singh, Pratul K Singh

  27. Silicon Nanowires- Properties Tiny PV Cells: Composed of 3 layers: • Inner P region • Intrinsic or pure silicon • Outer N region ICORE - 2010, Pragya Singh, Pratul K Singh

  28. Silicon Nanowires- Properties • Photon strikes the outer shell • Electron-hole pair is created • Travels in the radial direction towards the P layer (core) before recombination. ICORE - 2010, Pragya Singh, Pratul K Singh

  29. Silicon Nanowire based Solar Cells • Outline: • Light Trapping in Cells • Solar Cell • Energy Conversion in Solar Cell • Solar Cells Everywhere • Planar Silicon Solar Cell • Nanowires- Properties • Silicon Nanowires- Properties • Fabrication • Techniques for SiNW Deposition • Experiment at the SSN Research Centre ICORE - 2010, Pragya Singh, Pratul K Singh

  30. Fabrication • Catalyst Particles : • The catalyst must be inert to the reaction products (during CVD nanowire growth). • Gold • Aluminum • Tin • Indium • Gallium ICORE - 2010, Pragya Singh, Pratul K Singh

  31. Silicon Nanowire based Solar Cells • Outline: • Light Trapping in Cells • Solar Cell • Energy Conversion in Solar Cell • Solar Cells Everywhere • Planar Silicon Solar Cell • Nanowires- Properties • Silicon Nanowires- Properties • Fabrication • Techniques for SiNW Deposition • Experiment at the SSN Research Centre ICORE - 2010, Pragya Singh, Pratul K Singh

  32. Techniques for SiNW Deposition Techniques: • Supercritical-Fluid-Based and Solution-Based Growth Techniques • Molecular Beam Epitaxy • Laser Ablation • Silicon Monoxide Evaporation • PECVD ICORE - 2010, Pragya Singh, Pratul K Singh

  33. Silicon Nanowire based Solar Cells • Outline: • Light Trapping in Cells • Solar Cell • Energy Conversion in Solar Cell • Solar Cells Everywhere • Planar Silicon Solar Cell • Nanowires- Properties • Silicon Nanowires- Properties • Fabrication • Techniques for SiNW Deposition • Experiment at the SSN Research Centre ICORE - 2010, Pragya Singh, Pratul K Singh

  34. Experiment at the SSN Research Centre ICORE - 2010, Pragya Singh, Pratul K Singh

  35. Si-NW Growth Principle ICORE - 2010, Pragya Singh, Pratul K Singh

  36. Si-NW Deposition Process Steps • The sample introduced in the PECVD chamber • Heated to 580 degrees to form Nano particles • Silane introduced with hydrogen for 30 minutes at various temperatures Silicon (4 inch) n-type Substrate Cleaned Chromium layer of 10.7nm deposited by EBE Method Gold Layer of 2.6nm deposited by EBE Method ICORE - 2010, Pragya Singh, Pratul K Singh

  37. SiNW – Deposition Experiment • Catalyst Nano Particles: • Gold Film Layer (2.6nm) Deposited on Silicon Substrate by EBE • Heated at 580 degrees to form Nano Particles • Figure1 SEM image of Nano particles of Gold • Figure 1. SEM Image of Gold Nano Particles on Silicon Substrate ICORE - 2010, Pragya Singh, Pratul K Singh

  38. SiNW – Deposition Experiment PECVD system. Temperature : 380 degrees Pressure in mTorr : 500mT Time of Deposition : 30 minutes Gases Used : Silane, Hydrogen and Argon ICORE - 2010, Pragya Singh, Pratul K Singh

  39. Si NW Comparison Si Nano Wire at SSNRC Literature Survey Reference: IRAM, Saclay Institute of Matter and Radiation ICORE - 2010, Pragya Singh, Pratul K Singh

  40. Thank You ICORE - 2010, Pragya Singh, Pratul K Singh

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