Analysis of Carbon Nanotubes and Quantum Dots in a
Photovoltaic Device
Francis Smith
LSAMP Summer Program 2009Electrical Engineering Department
The City College of New York
Goal: Photovoltaic Device
Design and fabricate:
PHOTOVOLTAIC DEVICE
which is a type
of SOLAR CELL
using
CARBON NANOTUBES
&
QUANTUM DOTS
Single Walled Carbon Nanotubes (SWCNT)
• Single-layer graphene sheets rolled into cylinders
• Of a hexagonal mesh-like structure
• Of diameter between 0.33nm and 5nm
• Of length between 2nm and 10nm
• 50 times as strong as steel
• 1-dimensional structures (ballistic transport)
Cadmium Selenide Quantum Dots (CdSe QDs)
• Crystals (like salt), only nanometers in size
• 0-dimensional structures (quantum confinement)
• Of 2nm to 10nm (10-50 atoms) in diameter
• Large surface areato volume ratio:efficient light absorber
Methods ICdSe QD Preparation:
CDNTA + decylamine + Na2SeSO3 + Toluene
SWCNTA Preparation:
470oC oven + HCL + sonicate in DI H2O + centrifuge
Film Making:
Drop solution at 100rpm + 1000rpm (20sec)+ 200rpm (20min) + 2000rpm (5sec)
(aq) (aq)
Methods II
YAG Laser
Laser Attenuation Optics
Scanning PlatformComplete Z-Scan Setup
Testing (Z-Scan):
Results and Discussion I
Absorption Spectrum of CdSe QDs (aq)
Absorption Spectrum of SWCNTs (aq)
SPECTROSCOPY:
• Exciton peaks were expected and observed at approximately 415nm, 350nm and 380nm
• Therefore efficient absorption occurs at these wavelengths
• An absorption peak was expected and observed at approximately 440nm
• Therefore, efficient absorption occurs at this wavelength
Results and Discussion IIZ-SCAN:
Z-Scan of CS2 (aq) at 8uJ and 1064nm (infrared)
Z-Scan of CdSe QDs (aq) and13uJ at 532nm (green)
• The symmetricity and smoothness of this reference curve indicate good alignment and a stable beam
• Therefore, samples can now be scanned
• CdSe QD two photon absorption (TPA) curve
• This confirms the optical limiting property of QDs
MAXIMUM INTENSITY
INDIVIDUALLY TEST optical characteristics of CdSe QDs and SWCNTs in:
• Solution (raw)• Solution + PS (polystyrene)• Film 1 (from raw solution)• Film 2 (from solution + PS)
Future Work
1 2 3COMBINEQDs and SWCNTs and test all 4 combinations as in step 1
• FABRICATE Photovoltaic Cell with ITO electrodes
• CHARACTERIZE cell for energy conversion efficiency
References
[1]: B.J. Landi et al, Solar Energy Materials & Solar Cells 87 (2005) 733–746
[2]: Kanwal, Alokik. A Review of Carbon Nanotube Field Effect Transistors (Version 2.0).(2003).
[3]: “Quantum Dots Explained.” Evident Technologies. 2008. http://www.evidenttech.com/quantum-dots-explained.html. 06 July 2009.
[4]: Avila et al, Molecular Mechanics Applied to Single-Walled Carbon Nanotubes. Mat. Res. [online]. 2008, vol.11, n.3 [cited 2009-07-15], pp. 325-333
[5]: Pileni, Marie-Paule, Nature Materials 2, 145–150 (2003)
[6]: Chaiwat Engtrakul, et al, Self-Assembly of Linear Arrays of Semiconductor Nanoparticles on Carbon Single-Walled Nanotubes,J. Phys. Chem. B, 2006, 110 (50), 25153-25157
[7]: A. Kasuya et al.: Stoichiometric and ultra-stable nanoparticles of II-VI compound semiconductors, Eur. Phys. J. D 34, 39–41 (2005)
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