MoSx thin films were deposited on p-n GaInP photocathodes to improve their activity and stability for water splitting. A MoSx coating stabilized p-n GaInP and provided a photovoltage approaching that of PtRu-coated p-n GaInP. Additionally, sulfidizing Mo to form MoSx at 150°C produced similar results as 250°C, indicating compatibility with tandem device processing. While MoSx-coated p-n GaInP had lower photocurrent than PtRu-coated, thinning the MoSx film increased current without reducing photovoltage, demonstrating potential for optimization.
Superresolution Correlative Light and Electron Microscopy - DELMICDelmic B.V.
In recent years, super-resolution microscopy has proven itself to be an extremely powerful technique in biological research. With the invention of SR microscopy, it is now possible to precisely localize biomolecules at length scales that were previously only accessible using electron microscopy. Especially at this length scale, it is important to visualize and understand the microenvironment of these biomolecules; resolution only becomes truly valuable with contextual information.
The SECOM SR is an integrated platform for correlative light and electron microscopy which uses super-resolution (SR) optical microscopy in combination with an electron microscope. This system possesses all the features of the SECOM system, but is equipped with an extremely powerful optical microscope for yet more detail down to the nanoscale to study the complex relation between form and function in biology.
For questions about superresolution correlative microscopy and the SECOM SR, please leave a comment below or visit www.delmic.com and send us a message. We will respond to your questions as soon as possible!
CdSe Quantum Dot- Fullerene Hybrid Nano-
-composite for Solar Energy Conversion: Electron
Transfer and Photoelectrochemistry. Paper presentation, DOI: 10.1021/nn204350w
CVD grown nitrogen doped graphene is an exceptional visible-light driven phot...Pawan Kumar
The photocatalytic potential of large area CVD grown nitrogen doped graphene (NGr) has been explored though the chemical transformation of 4-nitrobenzene thiol into p, p'-dimercaptoazobenzene. Decoration of NGr with Ag nanocubes with rounded edges to form NGr/Ag nanohybrids resulted in a slight increase in the work-function and a decrease in the n-type character of NGr due to ground state transfer of negative charge from NGr to Ag. The Ag nanocubes exhibited a localized surface plasmon resonance (LSPR) at~ 425 nm. When the NGr/Ag nanohybrids were illuminated with visible light of wavelength close to the LSPR peak, Kelvin probe force microscopy (KPFM) indicated a dramatic change in surface potential of− 225 mV and Raman spectra detected electron accumulation in NGr, which are attributed to a high local field enhancement-mediated hot electron injection into NGr and the formation of long …
CVD grown nitrogen doped graphene is an exceptional visible-light driven phot...Pawan Kumar
The photocatalytic potential of large area CVD grown nitrogen doped graphene (NGr) has been explored though the chemical transformation of 4-nitrobenzene thiol into p,p'-dimercaptoazobenzene. Decoration of NGr with Ag nanocubes with rounded edges to form NGr/Ag nanohybrids resulted in a slight increase in the work-function and a decrease in the n-type character of NGr due to ground state transfer of negative charge from NGr to Ag. The Ag nanocubes exhibited a localized surface plasmon resonance (LSPR) at ~425 nm. When the NGr/Ag nanohybrids were illuminated with visible light of wavelength close to the LSPR peak, Kelvin probe force microscopy (KPFM) indicated a dramatic change in surface potential of −225 mV and Raman spectra detected electron accumulation in NGr, which are attributed to a high local field enhancement-mediated hot electron injection into NGr and the formation of long-lived charge separated states. Pristine nitrogen doped graphene and its coupled system with plasmonic Ag nanoparticles showed superior photocatalytic performance compared to bare plasmonic Ag catalyst. While standalone Ag NPs were unable to complete the transformation of 4-NBT into DMAB even at a laser power of 10 mW, NGr/Ag nanohybrids completed this transformation at a laser power of 1 mW, pointing to the high photoreduction strength of NGr/Ag. Density functional theory (DFT) based computational modeling was used to examine the electronic structure of graphene doped with graphitic, pyridinic and pyrrolic nitrogen dopant atoms. DFT results indicated an enhanced chemical reactivity of NGr due to stronger localization of charge at the dopant sites and a pronounced difference in the projected density of states (PDOS) for carbon atoms in proximity to, and distant from, the nitrogen dopant sites.
Copper (775) - an optics, 2PPE, and Bulk state simulation studyPo-Chun Yeh
My earlier studies on Cu(775) - a tilt cut highly crystalline copper surface using ultrafast femtosecond laser based 2-photon photoemission and its related simulation via Fortran 77.
A review on ipce and pec measurements and materials p.basnetPradip Basnet
The slides show how to measure the photoelectrochemical (PEC) properties of a light-active photocatalyst (usually semiconductor) and current literature summary for water splitting using sunlight.
Superresolution Correlative Light and Electron Microscopy - DELMICDelmic B.V.
In recent years, super-resolution microscopy has proven itself to be an extremely powerful technique in biological research. With the invention of SR microscopy, it is now possible to precisely localize biomolecules at length scales that were previously only accessible using electron microscopy. Especially at this length scale, it is important to visualize and understand the microenvironment of these biomolecules; resolution only becomes truly valuable with contextual information.
The SECOM SR is an integrated platform for correlative light and electron microscopy which uses super-resolution (SR) optical microscopy in combination with an electron microscope. This system possesses all the features of the SECOM system, but is equipped with an extremely powerful optical microscope for yet more detail down to the nanoscale to study the complex relation between form and function in biology.
For questions about superresolution correlative microscopy and the SECOM SR, please leave a comment below or visit www.delmic.com and send us a message. We will respond to your questions as soon as possible!
CdSe Quantum Dot- Fullerene Hybrid Nano-
-composite for Solar Energy Conversion: Electron
Transfer and Photoelectrochemistry. Paper presentation, DOI: 10.1021/nn204350w
CVD grown nitrogen doped graphene is an exceptional visible-light driven phot...Pawan Kumar
The photocatalytic potential of large area CVD grown nitrogen doped graphene (NGr) has been explored though the chemical transformation of 4-nitrobenzene thiol into p, p'-dimercaptoazobenzene. Decoration of NGr with Ag nanocubes with rounded edges to form NGr/Ag nanohybrids resulted in a slight increase in the work-function and a decrease in the n-type character of NGr due to ground state transfer of negative charge from NGr to Ag. The Ag nanocubes exhibited a localized surface plasmon resonance (LSPR) at~ 425 nm. When the NGr/Ag nanohybrids were illuminated with visible light of wavelength close to the LSPR peak, Kelvin probe force microscopy (KPFM) indicated a dramatic change in surface potential of− 225 mV and Raman spectra detected electron accumulation in NGr, which are attributed to a high local field enhancement-mediated hot electron injection into NGr and the formation of long …
CVD grown nitrogen doped graphene is an exceptional visible-light driven phot...Pawan Kumar
The photocatalytic potential of large area CVD grown nitrogen doped graphene (NGr) has been explored though the chemical transformation of 4-nitrobenzene thiol into p,p'-dimercaptoazobenzene. Decoration of NGr with Ag nanocubes with rounded edges to form NGr/Ag nanohybrids resulted in a slight increase in the work-function and a decrease in the n-type character of NGr due to ground state transfer of negative charge from NGr to Ag. The Ag nanocubes exhibited a localized surface plasmon resonance (LSPR) at ~425 nm. When the NGr/Ag nanohybrids were illuminated with visible light of wavelength close to the LSPR peak, Kelvin probe force microscopy (KPFM) indicated a dramatic change in surface potential of −225 mV and Raman spectra detected electron accumulation in NGr, which are attributed to a high local field enhancement-mediated hot electron injection into NGr and the formation of long-lived charge separated states. Pristine nitrogen doped graphene and its coupled system with plasmonic Ag nanoparticles showed superior photocatalytic performance compared to bare plasmonic Ag catalyst. While standalone Ag NPs were unable to complete the transformation of 4-NBT into DMAB even at a laser power of 10 mW, NGr/Ag nanohybrids completed this transformation at a laser power of 1 mW, pointing to the high photoreduction strength of NGr/Ag. Density functional theory (DFT) based computational modeling was used to examine the electronic structure of graphene doped with graphitic, pyridinic and pyrrolic nitrogen dopant atoms. DFT results indicated an enhanced chemical reactivity of NGr due to stronger localization of charge at the dopant sites and a pronounced difference in the projected density of states (PDOS) for carbon atoms in proximity to, and distant from, the nitrogen dopant sites.
Copper (775) - an optics, 2PPE, and Bulk state simulation studyPo-Chun Yeh
My earlier studies on Cu(775) - a tilt cut highly crystalline copper surface using ultrafast femtosecond laser based 2-photon photoemission and its related simulation via Fortran 77.
A review on ipce and pec measurements and materials p.basnetPradip Basnet
The slides show how to measure the photoelectrochemical (PEC) properties of a light-active photocatalyst (usually semiconductor) and current literature summary for water splitting using sunlight.
A NOVEL APPROACH TO OBTAIN MAXIMUM POWER OUTPUT FROM SOLAR PANEL USING PSOijsrd.com
The configuration of a most extreme force point following (MPPT) controller for a sun based photovoltaic force framework is proposed using a help converter topology utilizing PSO calculation. Sunlight based board voltage and current are consistently checked by a shut circle focused around PSO microcontroller control framework, and the obligation cycle of the help converter persistently changed in accordance with concentrate greatest force. Framework testing affirms crest force following under changing lighting conditions. Under particular conditions, efficiencies in overabundance of 96% are demonstrated to be conceivable.
Горбунов Н.А., Государственная морская академия им. С.О. Макарова, г. Санкт-Петербург
Разработка плазменных технологий для прямого фотоэлектрического преобразования с сфокусированного солнечного излучения
This presentation summarizes history and recent development of perovskite solar cells. If you have any questions or comments, you can reach me at agassifeng@gmail.com
Novel technique in charactarizing a pv module using pulse width modulatoreSAT Journals
Abstract The fabrication and characterization of PV modules are always done under standard test conditions (STC). However, The condition of operation are often far from thisstandard conditions. As a result, developing a characterization circuit is considered as a point of interest for researchers.This paper presents a new methodology in characterizing a PV module using an electronic load circuit. The circuit is implemented using a power MOSFET driven by a pulse width modulator (PWM) developed by LABVIEW. The system is tested and its results are validated by comparing it with simulation results performed by Comsol Multiphysics and Matlab. The system shows high accuracy with respect to the previous published work with lower cost and higher simplicity. Keywords: Photovoltaic, Characterization, Electronic load, and Pulse width modulation (PWM)…
Particle physics is now at the threshold of great discoveries. The experiments with particle accelerators and observations of the cosmos have focused attention on phenomena that can not be explained by the standard theory. The technology based on superconducting niobium accelerating cavities can reach a high expenditure of energy by many orders of magnitude lower than that of normal-conducting copper cavities. Even taking into account the power spent to maintain the temperature of liquid helium, the net gain in economic terms is still unassailable.
The sputtering technology was chosen first in the pure diode configuration and subsequently in the magnetron configuration. High Power Impulse Magnetron Sputtering (HIPIMS) is an evolution of the magnetron technique which relies on 100μs high voltage pulses of the order of 1 kV compared to the 300 V of the standard DC magnetron process. During the pulse a huge power density is deposited onto the target, of the order of a few kW/cm2 compared to a few W/cm2 of the standard DC process, producing a highly dense plasma in which also the Nb atoms are partially ionized. These can in turn be attracted to the substrate with a suitable bias. A further advantage of the technique lies in the fact that no hardware changes are required compared to a standard DC biased magnetron system, except for the obvious replacement of the power supply.
In this work, an R&D effort has been undertaken to study the HIPIMS, to improve it and understand the correlation between the parameters applied and the film morphology, the superconducting properties and the RF film quality.
The experiment system is based on the NEW HIGH-RATE SYSTEM for the deposition cavity 1.5 GHz. The experimental details and the measurements of the characteristics of the deposited films are described. Even though the work is still in progress, all of the partial results from now on have been analyzed and commented, in order to extrapolate all the information. The final results are a global overview of the HIPIMS techniques for Nb on 1.5Hz superconducting cavity. Suggestions for future efforts have been included as part of the conclusions.
1. Solar energy can only be generated when the sun is shining, but
the demand for energy exists without respite. This dilemma
motivates the development of solar energy storage technologies.
One method for storing energy from the sun is to transform
solar energy into chemical energy. PEC water-splitting devices
perform this transformation, outputting hydrogen gas. Hydrogen
is an energy carrier and can be used as a clean fuel and in the
production of fertilizers, among other applications.
Introduction
Results
MoSx thin films on hydrogen-evolving p-n GaInP photocathodes for improved activity and stability
David LaFehr1, James Young2, Reuben Britto1, Tom Jaramillo1, Todd Deutsch2
1Stanford University, Palo Alto, CA 2National Renewable Energy Laboratory, Golden, CO
This work was supported in part by the U.S. Department of Energy, Office of Science, Office of Workforce Development
for Teachers and Scientists (WDTS) under the Science Undergraduate Laboratory Internships Program (SULI).
Abstract
I would like to thank James Young, Todd Deutsch, and Reuben Britto for their guidance. I have also appreciated
the professional development pointers from Marcus Giron and Madison Martinez.
Conclusions & Future Work
Materials & Methods
Characterization TechniquesThree Electrode Setup
n-GaInP (25 nm) p-GaInP (1 µm)
p+-GaAs (625 µm?) Ti/Au
MoSx (~5 nm) PtRu (<1 nm)
NREL is a national laboratory of the U.S.
Department of Energy, Office of Energy
Efficiency and Renewable Energy, operated
by the Alliance for Sustainable Energy, LLC.
Photoelectrochemical (PEC) water-splitting is an
environmentally friendly way to obtain hydrogen, an energy-
dense fuel with a wide range of applications. The highest
efficiency PEC water-splitting devices employ tandem
absorbers, with a GaInP top junction in contact with electrolyte.
However, bare GaInP has low catalytic activity and low
stability. Previous work has shown that a thin film of MoSx,
applied to p-GaInP by sputtering of Mo and a subsequent
sulfidization anneal in H2S at 250°C for one hour, provides
stability and activity for the electrode. We investigated whether
MoSx also acts as a protective and catalytic coating on p-n
GaInP, employed to yield a photovoltage higher than that of p-
GaInP. Anticipating that 250°C is not compatible with future
tandem device processing requirements, we also compared the
performance of sulfidization at 250°C for one hour vs 150°C for
two hours. We found that MoSx-covered p-n GaInP is stable and
has a photocurrent onset potential higher than that of MoSx-
covered p-GaInP and rivaling that of PtRu. We also discovered
that there is no significant performance difference between
MoSx formed at 150°C and 250°C, verifying that future MoSx
processing can be carried out at 150°C. Finally, we show a
proof-of-concept that MoSx can be thinned to yield a much-
improved photocurrent while maintaining its impressive
photovoltage.
Objectives
1) Determine whether a coating of MoSx on p-n GaInP yields a stable and catalytic photocathode
2) Determine the impact of sulfidization at 150°C for two hours vs 250°C for one hour
The photocurrent onset potential of
250°C MoSx-covered p-n GaInP is
about 750 mV higher than that of
250°C MoSx-covered p-GaInP,
indicating more photovoltage and
better catalytic activity. There is
no difference in photovoltage
between MoSx formed at 150°C
and 250°C on p-n GaInP. This
photovoltage is higher than that for
PtRu-covered p-n GaInP, which is
impressive given that PtRu is the
standard catalytic coating for
GaInP.
Reflectance and IPCE measurements can explain the lower light-limited
photocurrent of MoSx-covered relative to PtRu-covered p-n GaInP. For all
wavelengths, both 150°C and 250°C MoSx-covered p-n GaInP have higher
reflectance and higher parasitic absorbance relative to PtRu-covered p-n GaInP.
Higher parasitic absorbance is indicated by lower internal quantum efficiency. The
reported internal quantum efficiency is not absolute, though, as reflectance
measurements were performed in air while IPCE data was taken with the sample
submerged in aqueous electrolyte.
A coating of MoSx on p-n GaInP stabilizes the electrode and yields a photovoltage approaching
and even surpassing that of PtRu-covered p-n GaInP. There is no significant performance
difference between MoSx formed at 150°C vs 250°C, verifying that tandem device processing
can occur at lower temperatures. Future work should focus on determining optimal thicknesses
of Mo and MoSx on GaInP.
The light-limited photocurrent for 150°C MoSx-covered p-n GaInP increases
substantially after three hours while the photocurrent onset potential shows no
change. So, there is a marked increase in solar-to-hydrogen efficiency after a few
hours. This is a proof-of-concept that the thickness of MoSx can be optimized to
yield increased current density with no drop in its catalytic activity.
Previous work has
shown that MoSx
formed at 250°C
provides stability to p-
GaInP for 70+ hours.
The same holds for
MoSx formed at 150°C
on p-n GaInP, as
evidenced by the
steady current in this
durability test*.
*Test is ongoing, data
will be available soon
Improving photocurrent and unchanging photovoltage
during operation
To do: add cartoon.
Wouldn’t the cartoon be
pretty similar to the one
I currently have
(reflection)?
LimitationsImproved stabilityImproved photovoltage
Background Motivation
Figure #. The
structure of an
inverted
metamorphic
multijunction cell.
Figure #. A stereoscopic image
of the surface of an IMM cell
that was annealed at 250°C.
The high temperature is
responsible for the wrinkles.2hν + H2O(l) → ½O2(g) + H2(g)
Figure #. Visualization of a PEC water-
splitting device. Light is incident on the
photoelectrode, and a the separation of
photogenerated holes and electrons creates
a voltage. If this voltage is above x V,
hydrogen evolution occurs on one
electrode and oxygen evolution takes place
on the other. The electrodes are submerged
in aqueous electrolyte to complete the
circuit.
Equation 1. Light and water react to
produce oxygen gas and hydrogen gas.
The most efficient PEC water-splitting device has a
photocathode consisting of p-GaInP/p+-GaAs, but it operates
for only a few hours before surface corrosion severely
degrades device performance. In the past, sputtered PtRu has
been employed to protect and provide activity to GaInP, but
its high cost makes it undesirable. MoSx, which is cheaper
than PtRu, has very recently been identified as a catalytic
coating on p-GaInP that stabilizes the device [1]. There are
two drawbacks to this setup, though: 1) MoSx-covered p-
GaInP does not have a very high photovoltage and 2) the
annealing of Mo to produce MoSx occurs at 250°C, a
temperature too high for future tandem device processing.
These drawbacks are the motivation for our work.
Figure #. The three electrode setup. Not shown are wires
that run from each of the electrodes to a potentiostat.
Photocathode Samples
Bare MoSx PtRu
Reflectance: Visible and
ultraviolet light were shined on the
sample. A photodetector measured
reflected light.
IPCE: Light of wavelengths 300-
720 nm, in increments of 10 nm,
was shined on the working
electrode. The steady-state current
for each wavelength was
measured. Same as EQE.
JV: The voltage between the
working and reference electrodes
was swept, each voltage yielding a
current between the working and
counter electrodes.
Durability: Galvanostatic and
potentiostatic measurements were
performed for 1-100 hours. JV
measurements were done
periodically.
Figures #a, b, and c. Figure
#c shows a possible
explanation for the relatively
low light-limited
photocurrent of MoSx-
covered p-n GaInP as seen
in Figure #a. In Figure #c,
due to reflection, less light
reaches the semiconductor
when it is coated with MoSx
(left) as opposed to PtRu
(right), corresponding to
generation of fewer charges.
Figure #b (IQE) suggests
that the poor photocurrent
can also be attributed to
parasitic absorbance.
a)
c)
b)To do: add
cartoon