Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Photocurrent”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Investigation on the AgPt and AgPd hybrid alloy nanoparticles (HANPs) for the hybrid MoS 2 /ZnO/HANP UV photodetector application

We report hybrid photodetectors made of two or more nanomaterial components can offer the high potential for advanced photodetection applications with enhanced light absorption, improved efficiency and structural tunability. A hybrid UV photodetector (PD) configuration incorporating the plasmonic hybrid alloy nanoparticles (HANP), ZnO quantum dots (QDs) and MoS 2 nanoflakes, namely MoS2/ZnO/HANP PD, is demonstrated. The optimized MoS 2 /ZnO/HANP PD exhibits a high photocurrent of 5.66 mA at 0.34 mW/mm 2 under 385 nm illumination with two orders of improvement from the bare ZnO, which is one of the highest photocurrents by the ZnO-based PDs. It also demonstrates high figure-of-merits with the responsivity of 14,523 mA/W, detectivity of 8.13 x 10 11 jones, and external quantum efficiency (EQE) of 4,680 %, outperforming most of the ZnO-based hybrid architectures. The enhanced photoresponse is primarily attributed to the significantly enhanced hot electron generation by the AgPd HANPs and photocarrier collection through the ZnO QD layer. MoS 2 nanoflakes also provide additional photon absorption sites and boost the photo-carrier transfer process. HANPs are grown by adapting a dual-step solid-state dewetting process (SSD) approach and the superiority of AgPd HANPs is confirmed by systematic investigation, FDTD simulation and comparison of AgPt and AgPd HANPs.

MoS2↗
DOE OSTI2020

The significance of the local structure of cobalt-based catalysts on the photoelectrochemical water oxidation activity of BiVO 4

The local structures of the water oxidation catalysts play an important role in reaction kinetics and the performance of the photoanodes. In this study, we deposited cobalt-based catalysts on nanoporous BiVO 4 with controlled thicknesses by atomic layer deposition (ALD). Despite the similar oxidation states of cobalt in all depositions, different water oxidation activities in neutral pH conditions were observed. Here, a dramatic photocurrent raise, lowered kinetic overpotential, and smaller charge transfer resistance across the photoanode/electrolyte interface were achieved when a uniform ultrathin Co(OH) 2 layer was formed on BiVO 4 . Photocurrent density for water oxidation showed a 95% enhancement at 0.6 V vs. RHE when the catalyst was in the form of Co(OH) 2 , while an 80% increase was obtained for CoO. Ideal coordination of Co(OH) 2 on hydroxylated BiVO 4 surface assists the charge transfer between the electrolyte and BiVO 4 without increasing surface recombination. The results of this study emphasize the importance of controlling the local structure of the catalysts in the performance of the water splitting photoanodes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

A hybrid CoOOH-rGO/Fe 2 O 3 photoanode with spatial charge separation and charge transfer for efficient photoelectrochemical water oxidation

As a promising photoanode for photoelectrochemical (PEC) water oxidation, hematite (Fe 2 O 3 ) still suffers from poor charge mobility and serious charges recombination and sluggish surface oxygen evolution kinetics. Herein, a hybrid photoanode of cobalt (oxy)hydroxide coupled with reduced graphene oxide modified Fe 2 O 3 (CoOOH-rGO/Fe 2 O 3 ) is well crafted by a facile hydrothermal synthesis with a chelation-mediated in-situ growth method. Morphology characterizations indicate rGO forms the internal network among isolated Fe 2 O 3 and CoOOH nanosheets distribute on the terminal of Fe 2 O 3 , forming a spatial separated nanostructure. The resultant CoOOH-rGO/Fe 2 O 3 exhibits an obviously reduced onset potential of ca. 150 mV and a significantly enhanced photocurrent density of 2.56 mA cm -2 at 1.23 V, which is ca. 3.3 times higher than that of bare Fe 2 O 3 . Especially, the functions of rGO and CoOOH are studied by using electrochemical impedance spectroscopy, open circuit potentials and intensity modulated photocurrent spectroscopy. It is found rGO act as conductive network which facilitates the electron transfer from Fe 2 O 3 to the substrate, while CoOOH evidently passivate the surface states of Fe 2 O 3 , improve charge separation and provide catalytic active sites for water oxidation. Additionally, the spatial charge separation and charge transfer caused by CoOOH and rGO are responsible for the enhanced PEC performance of water oxidation. The rational design and the facile fabrication strategy exhibit great potential to be used for other PEC system with great efficiency.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

MWCNT/WO{sub 3} nanocomposite photoanode for visible light induced water splitting

The Multi-walled carbon nanotube (MWCNT)/WO{sub 3} nanocomposite thin films with different MWCNT’s weight percentages were prepared by sol–gel method as visible light induced photoanode in water splitting reaction. Weight percentage of MWCNT in the all nanocomposite thin films was confirmed by TGA/DSC analysis. According to XPS analysis, oxygenated groups at the surface of the MWCNT and stoichiometric formation of WO{sub 3} thin films were determined, while the crystalline structure of the nanocomposite samples was studied by XRD indicating (0 0 2) peak of MWCNT in the monoclinic phase of WO{sub 3}. The influence of different weight percentage (wt%) of MWCNT on WO{sub 3} photoactivity showed that the electron conductivity, charge transfer and electron life time had improved as compared with the pure WO{sub 3}. Based on linear sweep voltammetry and chronoamperometry measurements, the (1 wt%) MWCNT/WO{sub 3} nanocomposite thin films photoanode has a maximum photocurrent density of ∼4.5 A/m{sup 2} and electron life time of about 57 s. - Graphical abstract: Photocurrent density versus time at constant potential (0.7 V) for the WO{sub 3} films containing different MWCNT weight percentages annealed at 400 °C under 1000 Wm{sup −2} visible photo-illumination. Display Omitted - Highlights: • MWCNT/ WO{sub 3} nanocomposite thin films were synthesized using sol–gel derived method. • TGA/DSC confirmed the weight percentage of MWCNT in the all nanocomposite thin films. • XPS analysis revealed that WO{sub 3} was attached on the oxygenated group of MWCNT surface. • The Highest Photoelectrochemical activity is achieved for (1 wt%)MWCNT/WO{sub 3} thin film.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2014

Production of core–shell type conducting FTO/TiO{sub 2} photoanode for dye sensitized solar cells

Core–shell type photoanode composed of electrically conducting fluorine doped tin dioxide (FTO) matrix and TiO{sub 2} shell layer was prepared and applied in dye sensitized solar cells. Effects of fluorine doping on tin dioxide based cells and precursor material on shell layer were investigated. Fluorine doped tin dioxide nanoparticles were synthesized under hydrothermal conditions and resistivity value down to 17 Ω cm was achieved. Cells constructed from FTO nanoparticles show enhanced performance compared to intrinsic SnO{sub 2}. Deposition of thin blocking TiO{sub 2} layers was conducted using ammonium hexafluorotitanate and titanium tetrachloride aqueous solutions for different dipping durations which yielded significant deviations in the layer morphology and affected cell parameters. Best results were obtained with titanium tetrachloride treated cells giving 11.51 mA/cm{sup 2} photocurrent density and they were comparable with that of pure TiO{sub 2} based cells prepared under identical conditions. - Graphical abstract: Core shell type FTO matrix was formed as TiO{sub 2} is the shell material to create a blocking layer between FTO core and the electrolyte for suppressed recombination and efficiency enhancement. Display Omitted - Highlights: • Core–shell type photoanode using conducting FTO matrix and TiO{sub 2} shell was prepared. • FTO nanoparticles having resistivity value down to 17 Ω cm was achieved. • Best cell parameters were obtained with TiCl{sub 4} treated cells. • FTO nanoparticle based cells show enhanced performance compared to intrinsic SnO{sub 2}. • Photocurrent in TiCl{sub 4} treated cells is found as comparable to pure TiO{sub 2} cell.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2016

Improved instrumentation for intensity-, wavelength-, temperature-, and magnetic field-resolved photoconductivity spectroscopy

We report instrumentation for photovoltage and photocurrent spectroscopy over a larger continuous range of wavelengths, temperatures, and applied magnetic fields than other instruments described in the literature: 350 nm≤λ≤1700 nm, 1.8 K≤T≤300 K, and B≤9 T. This instrument uses a modulated monochromated incoherent light source with total power<30 μW in combination with an LED in order to probe selected regions of non-linear responses while maintaining low temperatures and avoiding thermal artifacts. The instrument may also be used to measure a related property, the photomagnetoresistance. We demonstrate the importance of normalizing measured responses for variations in light power and describe a rigorous process for performing these normalizations. We discuss several circuits suited to measuring different types of samples and provide analysis for converting measured values into physically relevant properties. Uniform approaches to measurement of these photoproperties are essential for reliable quantitative comparisons between emerging new materials with energy applications. - Highlights: • A novel instrument for measuring photoconductivity and photocurrents of materials and devices. • Continuous parameter space: 350 nm≤λ≤1700, 1.8 K≤T≤300 K, and B≤9 T. • Methodology for treating non-linear responses and variable lamp intensity. • Mathematical detail for extracting properties of materials from measured values is provided.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Triazoloisoquinoline-based dual functional dyestuff for dye-sensitized solar cells

Graphical abstract: They consist of treating triazoloisoquinolines substituted tetramethyl-dioxaborolane (2) with 5-formyl-2-bromothiophene under conditions for Suzuki coupling to produce 5-(4-(3-oxo-[1,2,4]triazolo[3,4-a]isoquinolin-2(3H)-yl)phenyl) thiophene-2-carbaldehyde (3). Knoevenagel condensation of compound 3 with cyanoacrylic acid is carried out in the presence of piperidine, and after precipitation and purification with silica gel chromatography, the final dyestuff 4L is obtained as a yellow powder. This product has been characterized by spectroscopic analyses. Display Omitted Highlights: ► This new dyestuff investigated the role of triazoloisoquinoline dyestuffs as co-adsorbents and co-sensitizers with N719. ► The results show that co-adsorption of N719 sensitizer with dyestuff 5 increases the photocurrent in 1–0.25 molar ratio. ► This improved conversion efficiency is attributed to the insulating molecular layer, and the light harvesting effect at shorter-wavelength regions. -- Abstract: Triazoloisoquinoline contains electron-rich nitrogen and oxygen heteroatoms in a heterocyclic structure with high electron-donating ability. By utilizing this feature, two organic dyesutffs containing triazoloisoquinoline were synthesized and used in the fabrication of dye-sensitized solar cells (DSSCs), overcoming the deficiency of ruthenium dyestuff absorption in the blue part of the visible spectrum. This method also fills the blanks of ruthenium dyestuff sensitized TiO{sub 2} film, and forms a compact insulating molecular layer due to the nature of small molecular organic dyestuffs. The incident photon-to-electron conversion efficiency of N719 at shorter wavelength regions is 35%. After addition of triazoloisoquinoline-based dyestuff for co-sensitization, the IPCE at 350–500 nm increased significantly. This can be attributed to the increased photocurrent of the cells, which improves the dye-sensitized photoelectric conversion efficiency from 4.49% to 5.15%, which the overall conversion efficiency increased by about 15%. As a consequence, this low molecular weight organic dyestuff is a promising candidate as co-adsorbent and co-sensitizer for highly efficient dye-sensitized solar cells.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Photoelectrochemical properties of electrostatically self-assembled multilayer films formed by three bipolar hemicyanines and H{sub 4}SiW{sub 12}O{sub 40}

Graphical abstract: Display Omitted Highlight: ► Three self-assembled films of hemicyanines of and H{sub 4}SiW{sub 12}O{sub 40}. ► Uniformly deposited multilayers with reversible electrochemical activity. ► Large cathodic photocurrent densities of 0.36–1.02 μA/cm{sup 2} with IPCE of 0.75–0.98%. -- Abstract: The electrostatically self-assembled multilayer films of three bipolar hemicyanines with varied alkyl chain lengths were prepared by alternating adsorption of H{sub 4}SiW{sub 12}O{sub 40} and these hemicyanines, and characterized by UV–vis absorption spectroscopy, X-ray photoelectron spectroscopy and cyclic voltammetry. The results showed that these inorganic–organic composite films were uniformly deposited with good electrochemical activity. Photoelectrochemical investigations showed that the films exhibited large cathodic photocurrent densities of 0.36–1.02 μA/cm{sup 2} with the monochromatic incident photon-to-electron conversion efficiency of 0.75–0.98% while irradiated with 100 mW/cm{sup 2} polychromatic light (730 nm > λ > 325 nm) at an applied potential of −0.2 V vs. saturated calomel electrode, being strongly dependent on the alkyl chain lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Enhanced visible light photocatalytic hydrogen evolution of sulfur-doped polymeric g-C{sub 3}N{sub 4} photocatalysts

Graphical abstract: - Highlights: • Sulfur-doped g-C{sub 3}N{sub 4} was prepared using thiourea as sulfur source. • The sulfur-doped g-C{sub 3}N{sub 4} shows significantly enhanced H{sub 2} evolution activity. • The doped sulfur species plays key roles in the improvement of H{sub 2} production. • Photocatalytic mechanism is proposed based on the experimental results. • The mechanism is confirmed by PL spectra and transient photocurrent curves. - Abstract: Visible light-activated sulfur-doped g-C{sub 3}N{sub 4} photocatalysts were successfully synthesized using thiourea as sulfur source. The obtained photocatalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microcopy, ultraviolet–visible diffuse reflection spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy and transient photocurrent response. The sulfur-doped g-C{sub 3}N{sub 4} photocatalysts show beneficial effects on visible light absorption, electron–hole pair generation and separation. The sulfur species doped in the samples was identified as S{sup 2−} to replace N atoms in the g-C{sub 3}N{sub 4} framework. The photocatalytic activities of the sulfur-doped g-C{sub 3}N{sub 4} under visible light were evaluated by hydrogen evolution from water splitting in aqueous solution containing methanol. The sulfur-doped g-C{sub 3}N{sub 4} photocatalyst showed the highest photocatalytic performance with H{sub 2} evolution rate of 12.16 μmol h{sup −1}, about 6 times higher than un-doped g-C{sub 3}N{sub 4}. It can be concluded that the sulfur species play a vital role and act as active sites in the photocatalytic reaction. This novel sulfur-doped g-C{sub 3}N{sub 4} can be potentially used in energy and environmental applications.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Synthesis and characterization of g-C{sub 3}N{sub 4}/Cu{sub 2}O composite catalyst with enhanced photocatalytic activity under visible light irradiation

The prepared g-C{sub 3}N{sub 4}/Cu{sub 2}O composite exhibited the enhanced photocatalytic activity under visible-light irradiation due to the stronger ability in separation of electron–hole pairs, which was proven by the transient photocurrent measurement. - Highlights: • The coupled Cu{sub 2}O with g-C{sub 3}N{sub 4} of narrow-band-gap semiconductor has been designed. • g-C{sub 3}N{sub 4}/Cu{sub 2}O is prepared via an alcohol-aqueous based on chemical precipitation method. • g-C{sub 3}N{sub 4}/Cu{sub 2}O exhibits the enhanced photocatalytic activity under visible-light. • The enhanced photocatalytic activity is proven by the transient photocurrent test. • A mechanism for the visible-light-driven photocatalysis of g-C{sub 3}N{sub 4}/Cu{sub 2}O is revealed. - Abstract: To overcome the drawback of low photocatalytic efficiency brought by electron–hole pairs recombination and narrow photo-response range, a novel g-C{sub 3}N{sub 4}/Cu{sub 2}O composite photocatalyst was designed and prepared successfully. Compared with bare Cu{sub 2}O and g-C{sub 3}N{sub 4}, the g-C{sub 3}N{sub 4}/Cu{sub 2}O composite exhibited significantly enhanced photocatalytic activity for acid orange-II (AO-II) degradation under visible light irradiation. Based on energy band positions, the mechanism of enhanced visible-light photocatalytic activity was proposed.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Ultra-thin g-C{sub 3}N{sub 4} nanosheets wrapped silicon nanowire array for improved chemical stability and enhanced photoresponse

Highlights: • g-C{sub 3}N{sub 4}, as an oxygen free and metal free protective material for Si, was proposed. • g-C{sub 3}N{sub 4} nanosheets wrapped Si nanowire array was synthesized. • SiNW/g-C{sub 3}N{sub 4} exhibited enhancement of photoelectrochemical stability and photocurrent. - Abstract: In order to inhibit the oxidation of Si materials in aqueous solution, Si nanowire array was wrapped by ultra-thin g-C{sub 3}N{sub 4} nanosheets via an electrophoresis process. Scanning electron microscopy and transmission electron microscopy images showed that g-C{sub 3}N{sub 4} nanosheets were evenly distributed on the surface of Si nanowire array. X-ray diffraction patterns indicated that Si nanowire array/g-C{sub 3}N{sub 4} nanosheets were composed of Si (4 0 0 crystal plane) and g-C{sub 3}N{sub 4} (0 0 2 and 1 0 0 crystal planes). The cyclic voltammetry curves revealed that the corrosion of Si nanowire array was restrained under the protection of g-C{sub 3}N{sub 4} nanosheets. Furthermore, the photocurrent density of Si nanowire array/g-C{sub 3}N{sub 4} nanosheets increased by nearly 3 times compared to that of bare Si nanowire array due to the effective charge separation caused by the built-in electric field at the interface. This work will facilitate the applications of Si materials in aqueous solution, such as solar energy harvest and photocatalytic pollution control.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Facile synthesis of Ag–Cu{sub 2}O composites with enhanced photocatalytic activity

Highlights: • Ag–Cu{sub 2}O nanocomposites were synthesized via awet-chemical precipitation route. • The growth temperature does not exceed 50 °C in any step of the synthesis. • Enhanced photocurrent of Ag–Cu{sub 2}O composites, compared to pure Cu{sub 2}O particles. • The photocatalytic property was studied upon simulated sunlight. • Enhanced photocatalytic property of Ag–Cu{sub 2}O composites, compared to pure Cu{sub 2}O particles. - Abstract: Silver–cuprous oxide (Ag–Cu{sub 2}O) microcomposites are successfully prepared by a facile low-cost solution method. The obtained materials were characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), field emission scanning electron microscopy (FESEM), ultraviolet–visible (UV–vis) spectroscopy, X-ray photoelectron spectroscopy (XPS). Experiments demonstrated that the formation of Ag–Cu{sub 2}O microcomposites was significantly influenced by the concentration of AgNO{sub 3}, and with increasing the concentration of AgNO{sub 3}, the optical absorption of the composites becomes strong. The photocatalytic activity of the prepared Ag–Cu{sub 2}O composites was determined by measuring the degradation of methyl orange solution under visible light, to find out its potential application in waste water treatment. The results reveal that the photocurrent of the composite is about 4 times higher than that of pure Cu{sub 2}O and the visible light photocatalytic activity of the composite is enhanced greatly on degradation of methyl orange. The reason for improvement in photocatalytic activity of the Ag–Cu{sub 2}O composites was also discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Fabrication of uniformly dispersed Ag nanoparticles loaded TiO{sub 2} nanotube arrays for enhancing photoelectrochemical and photocatalytic performances under visible light irradiation

Graphical abstract: Uniformly dispersed Ag nanoparticles (NPs) were successfully loaded on both the outer and inner surface of the TiO{sub 2} nanotube arrays (NTs) through a simple polyol method, which exhibited the enhanced photoelectrochemical and photocatalytic performances under visible-light irradiation due to the more effective separation of photo-generated electron–hole pairs and faster interfacial charge transfer. - Highlights: • Highly dispersed Ag nanoparticles (NPs) are successfully prepared by polyol method. • Ag NPs are uniformly loaded on the surface of the TiO{sub 2} nanotube arrays (NTs). • Ag/TiO{sub 2}-NTs exhibit the enhanced photocatalytic activity under visible-light. • The enhanced photocurrent is explained by electrochemical impedance spectroscopy. - Abstract: Uniformly dispersed Ag nanoparticles (NPs) were successfully loaded on both the outer and inner surface of the TiO{sub 2} nanotube arrays (NTs) through a simple polyol method. The as-prepared Ag/TiO{sub 2}-NTs were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV–vis diffusion reflectance spectroscopy. Photoelectrochemical behaviors were investigated via photocurrent response and electrochemical impedance spectroscopy (EIS). Photocatalytic activity of Ag/TiO{sub 2}-NTs was evaluated by degradation of acid orange II under visible light irradiation. The results showed that photocatalytic efficiency of Ag/TiO{sub 2}-NTs is more than 5 times higher than that of pure TiO{sub 2} NTs. Comparing with the electrochemical deposition method, the photocatalytic activity of Ag/TiO{sub 2}-NTs prepared by polyol method has been obviously increased.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Fabrication and efficient photocatalytic activity of porous CdS-pillared tetratitanate nanohybrid

Highlights: • Heterostructured CdS–H{sub 2}Ti{sub 4}O{sub 9} nanohybrid exhibits a wide spectral response. • The nanohybrid gave a H{sub 2} evolution rate of 895 μmol h{sup –1} g{sup –1} in water splitting. • The electronic coupling was evidenced by XPS and photocurrent results. - Abstract: Heterostructured CdS-pillared tetratitanate nanohybrid was fabricated by electrostatically driven self-assembly of the exfoliated tetratitanate nanosheets and CdS nanosol particles. It was revealed that the present nanohybrid is porous with a specific surface area of 65 m{sup 2} g{sup −1} and that the tetratitanate nanosheets were restacked in a well-ordered arrangement with a gallery height of 2.3 nm. The formation of an electronic coupling between the titanate nanosheets and the encapsulated CdS pillars was supported by XPS and photocurrent measurements. The nanohybrid exhibits a highly photocatalytic activity of 895 μmol h{sup −1} g{sup −1} in H{sub 2} evolution from water splitting under 300 W Xe lamp irradiation, which is about 11 and 7 times higher than its parents H{sub 2}Ti{sub 4}O{sub 9}·H{sub 2}O and CdS, respectively. Loading 3 wt% Pt resulted in that its activity was further improved to 1897 μmol h{sup −1} g{sup −1}. It was showed that the as-prepared nanohybrid has an excellent stability and recurrence performance in hydrogen generation.

36 MATERIALS SCIENCE↗
DOE OSTI2017

All-vanadium photoelectrochemical storage cells using dye sensitized geometry-enhanced TiO{sub 2} nanobelts

Highlights: • Dye-sensitized photoelectrode using nanostructured anatase TiO{sub 2} nanobelts was studied in photoelectrochemical storage cells. • An intricate balance between a series of charge-transfer processes related to the dye sensitizer, redox species, and photoelectrode was discovered. • Under AM1.5 illumination rapid charge transfer in the 1D nanobelts enhances photocurrent. • Large specific surface area of the photoelectrode dominates the performance under visible light. - Abstract: Photoelectrochemical (PEC) devices, which use solar energy to drive charge transfer, have been considered as a low cost and effective approach to harvest energy from the sun. Dye sensitization designs are promising alternative to traditional semiconductor-based cells, as they can absorb a wide spectrum of light and provide free energy for PEC reactions. However, an intricate balance exists between a number of series charge-transfer processes related to the dye sensitizer, redox species, and photoelectrode. Here, we study a dye-sensitized photoelectrode using nanostructured anatase TiO{sub 2} nanobelts (TNBs) in the newly developed all-vanadium PEC storage cell (all-V PESC) to understand the performance dominating factor as well as to enhance photoexcitation and charge transfer, thus the solar energy storage efficiency. Preliminary results show enhanced photocurrent and reduced charge transfer resistance under AM1.5 illumination upon dye sensitization. Under visible light, however, large specific surface area of the photoelectrode seems to dominate the PEC performance.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Photovoltaic performance of Ag-doped CdS quantum dots for solar cell application

Graphical abstract: Photovoltaic performance of un-doped and Ag-doped CdS quantum dots were studied. The enhancement in photovoltaic performance might be due to the increase in carrier concentration and additional energy level creation due to Ag doping in FTO/TiO{sub 2}/Ag-doped CdS QDs solar cell. - Highlights: • Un-doped and Ag-doped CdS QDs were successfully deposited on TiO{sub 2}/FTO. • Optical response was found to be high for 3% Ag-doped CdS QDs. • The absorption edge for the 3% Ag-doped CdS was found to be 550 nm. • The highest power conversion efficiency was 1.25% for 3% Ag-doped CdS QDs. - Abstract: Un-doped and Ag-doped CdS quantum dots (QDs) were deposited on spin coated TiO{sub 2} photoanode material by Successive Ionic Layer Adsorption and Reaction (SILAR) method. Systematic investigations were carried out in the deposited un-doped and Ag-doped CdS QDs using powder X-ray diffraction (PXRD), field emission scanning electron microscopy (FESEM) and UV–vis-NIR spectrum. Finally, the FTO/TiO{sub 2}/un-doped CdS and FTO/TiO{sub 2}/Ag-doped CdS QDs were successfully assembled to study the photovoltaic performance under standard one sun illumination of AM 1.5, 100 mW/cm{sup 2}. Photovoltaic parameters, such as short-circuit photocurrent density, open circuit voltage, fill factor and conversion efficiency were found to be 1.37 mA/cm{sup 2}, 0.72 V, 61.5% and 0.61% respectively, for un-doped CdS. Ag-doped CdS QDs shows enhanced photovoltaic parameters such as short-circuit photocurrent density, open circuit voltage, fill factor and conversion efficiency which were 2.35 mA cm{sup 2}, 0.74 V, 71.8% and 1.25% respectively.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Phenomenal improvement of external quantum efficiency, detectivity and responsivity of nitrogen doped graphene quantum dot decorated zinc oxide nanorod/polymer schottky junction UV detector

Highlights: • ZnO nanorods/conducting polymer Schottky junction UV detector was fabricated. • GQDs and NGQDs were attached with nanorods to improve the detector performance. • The photodetector demonstrated high EQE, detectivity and responsivity. • NGQDs sensitized nanorod based detectors showed superior performances. • NGQD sensitized device showed high photocurrent even at lower intensity of UV light. - Abstract: Photodetector properties of nitrogen doped graphene quantum dot (NGQD) sensitized ZnO nanorods/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) Schottky junction has been investigated. The photodetector demonstrated superior external quantum efficiency (EQE) (∼57681% at −1 V bias) at wavelength ∼340 nm, which is 4 times higher than graphene quantum dot (GQD) modified ZnO NRs based detector and 35 times higher than pristine ZnO NRs detector. NGQD modified detectors also showed higher responsivity (∼158 A/W), detectivity (8.7 × 10{sup 12} Hz{sup 1/2}/W) at 340 nm wavelength. The response and recovery times of the detector is very fast compared to GQD modified and pristine ZnO nanorod based detectors. Our UV detector also demonstrated higher photocurrent even at lower intensity range of incident light.

36 MATERIALS SCIENCE↗