Silicon Nanowire based Solar Cells International Congress On Renewable Energy ICORE 2010 2nd 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 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

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

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

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

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

ICORE - 2010, Pragya Singh, Pratul K Singh 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

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

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

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

Solar Cells Everywhere Safe Clean Quiet Durable Reliable Installable anywhere ICORE - 2010, Pragya Singh, Pratul K Singh

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

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

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

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

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

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

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

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

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

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

Silicon Nanowires- Properties Reduced Recombination in SiNW: Small diameters. SiNWs grown 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

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

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

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

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

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

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

ICORE - 2010, Pragya Singh, Pratul K Singh 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

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

Techniques for SiNW Deposition Supercritical-Fluid-Based and Solution-Based Growth Techniques Molecular Beam Epitaxy Laser Ablation Silicon Monoxide Evaporation PECVD ICORE - 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 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

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

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

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

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

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

ICORE - 2010, Pragya Singh, Pratul K Singh 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

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