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Silicon Nanowire based Solar Cells. ICORE - 2010, Pragya Singh, Pratul K Singh. Outline:Light Trapping in CellsSolar CellEnergy Conversion in Solar CellSolar Cells EverywherePlanar Silicon Solar CellNanowires- PropertiesSilicon Nanowires- PropertiesFabricationTechniques for SiNW DepositionExperiment at the SSN Research Centre.
 
                
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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. ICORE - 2010, Pragya Singh, Pratul K Singh 
3. Silicon Nanowire based Solar Cells ICORE - 2010, Pragya Singh, Pratul K Singh 
4. ICORE - 2010, Pragya Singh, Pratul K Singh 
5. ICORE - 2010, Pragya Singh, Pratul K Singh 
6. Silicon Nanowire based Solar Cells 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 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 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 ICORE - 2010, Pragya Singh, Pratul K Singh 
13. Silicon Nanowire based Solar Cells ICORE - 2010, Pragya Singh, Pratul K Singh 
14. ICORE - 2010, Pragya Singh, Pratul K Singh 
15. Sliced into Nano-scale ICORE - 2010, Pragya Singh, Pratul K Singh 
16. ICORE - 2010, Pragya Singh, Pratul K Singh 
17. ICORE - 2010, Pragya Singh, Pratul K Singh 
18. Silicon Nanowire based Solar Cells ICORE - 2010, Pragya Singh, Pratul K Singh 
19. 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 Nanowires- Properties 
20. Silicon Nanowire based Solar Cells ICORE - 2010, Pragya Singh, Pratul K Singh 
21. 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 
22. 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. 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 
24. 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. 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. ICORE - 2010, Pragya Singh, Pratul K Singh Silicon Nanowires- Properties 
27. 
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. 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 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 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 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 ICORE - 2010, Pragya Singh, Pratul K Singh 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 
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
 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  ICORE - 2010, Pragya Singh, Pratul K Singh 
40. Thank You  ICORE - 2010, Pragya Singh, Pratul K Singh