Photovoltaic cells fabricated by electrophoretic deposition

Nathanael J. Smith, Kevin J. Emmett, and Sandra J. Rosenthal

Purpose

The purpose of this paper is to observe the efficiency of photovoltaic cells made with CdSe nanocrystals that have been electrophoretically deposited onto titanium oxide. The efficiency of these cells are lower to other solar cells (~10^-6%).

Methods/Procedures Used

Electrophoresis was used to deposit the CdSe nanocrystals in a fast and non-destructive manner. Rutherford backscattering was used to compare the composition of the films on both the positive and negative electrodes during the deposition.

Key Findings

1. Too much TOPO solvent made electrophoresis difficult. This is due to an effect seen in previous literature where CdSe prefer to stay in solution.
2. An interesting effect was observed where cadmium precursor attaches to the negative electrode during deposition in a greater concentration than onto the positive electrode. This concentration difference was determined by Rutherford backscattering
3. Nanometer thick photovoltaic cells were successfully created within one minute with this technique.

Flexible deposition of nanocrystalline vanadium oxide thin films

Yuri Diaz-Fernandez , Lorenzo Malavasi * and Eliana Quartarone

J. Mater. Chem., 2008, 18, 5190-5192

Purpose

The purpose of this study is to deposit 100nm films of various vanadium oxides (V2O3, VO2, V2O5) on the same substrate and measure the differences of thickness and composition that can occur when the rf sputtering power is changed.

Methods and Procedures

The films were made by rf magnetron sputtering onto quartz and aluminum oxide substrates. By changing the substrate temperature, rf power and oxygen partial pressure, the researchers changed the ratio of the oxide composition. The crystalline nature of the films were determined by x-ray diffraction. The roughness and imaging were determined by atomic force microscopy.

Key Findings

As the rf power increases, the film density and roughness of the film goes down. This is under further investigation to be included in a subsequent full paper.

Structural Transition in Nanostructured Eu2O3 Under High Pressures

Purpose:

The purpose of this study was to observe how the crystal structure of Europium oxide nanoparticles changed under high pressures.

Methods and Procedures Used

A Mao Bell type diamond anvil cell was used to exert high pressure on the nanoparticles. X-ray diffraction was used to perform structural studies on the samples. Raman spectrometry was used to determine the geometry of the nanoparticles before and after the high pressures were exerted. Atomic force microscopy was used to image the nanoparticles. X-ray photoelectron spectroscopy was used to compare phases of the material before and after the high pressure treatment.

Key Findings

The oxide changed from cubic to monoclinic at 8 GPa.

SYNTHESIS OF MONODISPERSE SUB-3 NM RE2 O3 AND GD2 O3 :RE3 +

SYNTHESIS OF MONODISPERSE SUB-3 NM RE2 O3 AND GD2 O3 :RE3 +
NANOCRYSTALS
S.V. MAHAJAN AND J.H. DICKERSON
Nanotechnology 18 (2007) 325605 (6pp)

Purpose
The purpose of this paper was to investigate synthetic methods that would yield sub-3nm monodispersed europium sequioxide, terbium sequioxide, RE3 +-doped gadolinium or yttrium sequioxides.
Methods
Several characterization techniques were used to investigate the particles. FTIR was
used to determine the molecular binding energy of the organic ligand to the surface of the material. XRD was used to determine the cubic structure of the material. TEM was used to determine the size and size distribution of the material. Spectrophotofluorometer was used to determine the absorption and emission spectra of the material. Thermogravimetric analysis was used to determine the decomposition temperature of the material.
Key Findings
• The thermal stabilities of all the particles studied are similar.
• The cubic structure for all the particles studied is body centered cubic.
• Luminescence studies show that this property is size-dependent.
• Beginning oleic acid is related to nanocrystal size.
Definitions
• RE : rare earth metals. In this paper, that would mean europium, terbium and
gadolinium.
• Sesquioxides : molecule that has three oxygens and two of another element. In this
paper, that would mean Eu2 O3 . Other examples include aluminum oxide, Al2 O3 .
• FTIR : Fourier transform infrared spectrophotometer
• XRD : X-ray Diffractometer
• TEM : Tunneling Electron Microscope