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)