Analysis Of Carbon Nanotubes And Quantum Dots In A Photovoltaic Device Slide Presentation

Analysis of Carbon Nanotubes and Quantum Dots in a Photovoltaic Device Francis Smith LSAMP Summer Program 2009 Electrical 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 area to volume ratio: efficient light absorber

Methods I

CdSe QD Preparation :

CDNTA + decylamine + Na 2 SeSO 3 + Toluene

SWCNTA Preparation :

470 o C oven + HCL + sonicate in DI H 2 O + centrifuge

Film Making :

Drop solution at 100rpm + 1000rpm (20sec) + 200rpm (20min) + 2000rpm (5sec)

(aq) (aq)

Methods II YAG Laser Laser Attenuation Optics Scanning Platform Complete 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 II Z-SCAN : Z-Scan of CS 2 (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

Future Work

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)

1 2 3 COMBINE QDs 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)