23 research outputs found
Thiol-Terminated Di-, Tri-, and Tetraethylene Oxide Functionalized Gold Nanoparticles:Â A Water-Soluble, Charge-Neutral Cluster
Control of PbSe Nanorod Aspect Ratio by Limiting Phosphine Hydrolysis
The
aspect ratio and yield of PbSe nanorods synthesized by the
reaction of Pb-oleate with trisÂ(diethylamino)Âphosphine selenide are
highly sensitive to the presence of water, making it critical to control
the amount of water present in the reaction. By carefully drying the
reaction precursors and then intentionally adding water back into
the reaction, the nanorod aspect ratio can be controlled from 1.1
to 10 and the yield from 1 to 14% by varying the water concentration
from 0 to 204 mM. <sup>31</sup>PÂ{<sup>1</sup>H} and <sup>1</sup>H
NMR show that water reacts with trisÂ(diethylamino)Âphosphine to create
bisÂ(diethylamido)Âphosphorous acid. It was determined that bisÂ(diethylamido)Âphosphorous
acid is responsible for the observed aspect ratio and yield changes.
Finally, it was found that excess oleic acid in the reaction can also
react with trisÂ(diethylamino)Âphosphine to create bisÂ(diethylamido)Âphosphorous
acid, and upon the removal of both excess oleic acid and water, highly
uniform, nonbranching nanorods were formed
Synthesis and Optical Properties of PbSe Nanorods with Controlled Diameter and Length
The
synthesis of PbSe nanorods with low branching (<1%), high
aspect ratios (up to âŒ16), and controlled lengths and diameters
was demonstrated via the removal of water and oleic acid from the
synthesis precursors. It was determined that the proper combination
of reaction time and temperature allows for the control of PbSe nanorod
length and diameter and therefore control over their electronic states,
as probed through absorbance and photoluminescence measurements. Similar
to PbSe nanowires, nanorods display higher Stokes shifts than for
spherical nanocrystals due to intrananorod diameter fluctuations
Impact of Nanocrystal Spray Deposition on Inorganic Solar Cells
Solution-synthesized inorganic cadmium
telluride nanocrystals (âŒ4 nm; 1.45 eV band gap) are attractive
elements for the fabrication of thin-film-based low-cost photovoltaic
(PV) devices. Their encapsulating organic ligand shell enables them
to be easily dissolved in organic solvents, and the resulting solutions
can be spray-cast onto indiumâtin oxide (ITO)-coated glass
under ambient conditions to produce photoactive thin films of CdTe.
Following annealing at 380 °C in the presence of CdCl<sub>2(s)</sub> and evaporation of metal electrode contacts (glass/ITO/CdTe/Ca/Al),
Schottky-junction PV devices were tested under simulated 1 sun conditions.
An improved PV performance was found to be directly tied to control
over the film morphology obtained by the adjustment of spray parameters
such as the solution concentration, delivery pressure, substrate distance,
and surface temperature. Higher spray pressures produced thinner layers
(<60 nm) with lower surface roughness (<200 nm), leading to
devices with improved open-circuit voltages (<i>V</i><sub>oc</sub>) due to decreased surface roughness and higher short-circuit
current (<i>J</i><sub>sc</sub>) as a result of enhanced
annealing conditions. After process optimization, spray-cast Schottky
devices rivaled those prepared by conventional spin-coating, showing <i>J</i><sub>sc</sub> = 14.6 ± 2.7 mA cm<sup>â2</sup>, <i>V</i><sub>oc</sub> = 428 ± 11 mV, FF = 42.8 ±
1.4%, and Eff. = 2.7 ± 0.5% under 1 sun illumination. This optimized
condition of CdTe spray deposition was then applied to heterojunction
devices (ITO/CdTe/ZnO/Al) to reach 3.0% efficiency after light soaking
under forward bias. The film thickness, surface morphology, and light
absorption were examined with scanning electron microscopy, optical
profilometry, and UV/vis spectroscopy
Isolation and Characterization of Trioxyethylene-Encapsulated Gold Nanoclusters Functionalized with a Single DNA Strand
Synthesis and Characterization of Potential Single-Source Precursors to Group 13âAntimonides
Inorganic Photovoltaic Devices Fabricated Using Nanocrystal Spray Deposition
Soluble
inorganic nanocrystals offer a potential route to the fabrication
of all-inorganic devices using solution deposition techniques. Spray
processing offers several advantages over the more common spin- and
dip-coating procedures, including reduced material loss during fabrication,
higher sample throughput, and deposition over a larger area. The primary
difference observed, however, is an overall increase in the film roughness.
In an attempt to quantify the impact of this morphology change on
the devices, we compare the overall performance of spray-deposited
versus spin-coated CdTe-based Schottky junction solar cells and model
their dark currentâvoltage characteristics. Spray deposition
of the active layer results in a power conversion efficiency of 2.3
± 0.3% with a fill factor of 45.7 ± 3.4%, <i>V</i><sub>oc</sub> of 0.39 ± 0.06 V, and <i>J</i><sub>sc</sub> of 13.3 ± 3.0 mA/cm<sup>2</sup> under one sun illumination