Effect of electron-phonon interaction and valence band edge shift for carrier-type reversal in layered ZnS/rGO nanocomposites

Natarajan, Vanasundaram; Kumar, Prashant; Ahmad, Mifrah; Sharma, Jitender Paul; Chaudhary, A.K.; Kumar, Praveen

doi:10.1016/j.jcis.2020.10.067

Cited by 15 publications

(8 citation statements)

References 43 publications

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“…Therefore, the Δ E Ga 3d GaN was estimated to be 17.45 eV. Further, it has been reported for the rGO film that the peak of the C 1s core level exists at a binding energy of 285.11 eV . From our previous studies of the valence-band spectra of rGO, the value of E VBM was found to be 2.0 eV .…”

Section: Resultsmentioning

confidence: 88%

Hybrid Reduced Graphene Oxide/GaN Nanocolumns on Flexible Niobium Foils for Efficient Photoelectrochemical Water Splitting

Ramesh

Tyagi

Aggarwal

et al. 2023

ACS Appl. Nano Mater.

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We present the photoelectrochemical (PEC) watersplitting properties of pristine and reduced graphene oxide (rGO)coated GaN nanocolumns (NCs) on flexible niobium (Nb) metal foils. The structural, optical, and electronic structure analyses of rGOcoated GaN-NCs on Nb foils revealed the formation of a rGO/GaN-NCs hybrid structure. Further, the valence-band studies of pure GaN-NCs shows valence-band maxima at ∼3.0 eV below the Fermi level, which decreased to ∼2.8 eV for rGO/GaN-NCs. The PEC measurement performed on pristine GaN-NCs under standard (1 Sun) conditions shows an effective photocatalytic nature with a photocurrent density of ∼60 μA/cm 2 at 0.8 V (vs Ag/AgCl) in a 1 M oxalic acid electrolyte, which increases to ∼110 μA/cm 2 for rGO/ GaN-NCs. The efficient PEC characteristics of rGO/GaN-NCs are attributed to the effective charge separation/transport of photogenerated carriers. Furthermore, transient photocurrent measurement reveals that hybrid and pristine GaN-NCs on flexible metal foil have a fast and stable photoresponse in an aqueous solution. The development of a hybrid nitride nanostructure-based PEC device on flexible metal foils paves the way toward developing scalable PEC devices for hydrogen production applications.

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Section: Resultsmentioning

confidence: 88%

Hybrid Reduced Graphene Oxide/GaN Nanocolumns on Flexible Niobium Foils for Efficient Photoelectrochemical Water Splitting

Ramesh

Tyagi

Aggarwal

et al. 2023

ACS Appl. Nano Mater.

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“…In case of light absorption in the GaAs/AlSb (GaAs/AlAs) heterostructures, the phonon absorption and phonon emission of GaAs and AlSb (AlAs) atomic layers influences the absorption onset, since the interface band gap and phonon density varies as number of atomic layers changes [31,33]. Electronphonon interactions in each atomic layer can affect the light absorption [45,46]. The phonon density is higher in the GaAs atomic layers as compared to AlSb and AlAs atomic layers and as a result, GaAs atomic layers electron-phonon interaction may actively influence the light absorption.…”

Section: Optical Propertiesmentioning

confidence: 99%

Influence of temperature on bandgap shifts, optical properties and photovoltaic parameters of GaAs/AlAs and GaAs/AlSb p–n heterojunctions: insights from ab-initio DFT + NEGF studies

Mamindla,

Niranjan

2024

J. Phys.: Condens. Matter

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The III-V group semiconductors are highly promising absorbers for heterojunctions based solar cell devices due to their high conversion efficiency. In this work, we explore the solar cell properties and the role of electron-phonon coupling on the solar cell parameters of GaAs/AlSb and GaAs/AlAs p-n heterojunctions using non-equilibrium Green function method (NEGF) in combination of ab-initio density functional theory (DFT). In addition, the band offsets at the heterointerfaces, optical absorption and bandgap shifts due to temperature are estimated using DFT+NEGF approach. The interface band gaps in heterostructures are found to be lower than bulk band gaps leading to a shift in optical absorption coefficient towards lower energy side that results in stronger photocurrent. The temperature dependent electronic band gap shift is significantly influenced by the phonon density and phonon energy via electron phonon coupling. The phonon influenced band gap shift is found to change the optical absorption, photocurrent density and open-circuit voltage. In case of GaAs/AlSb junction, the interface phonons are found to have significantly higher energies as compared to bulk phonons and thereby may have important implications for photovoltaic properties. Overall, the present study reveals the influence of electron-phonon coupling on the optical absorption and photovoltaic properties of GaAs/AlSb and GaAs/AlSb p-n heterojunctions. Furthermore, the study shows that the DFT+NEGF method can be successfully used to obtain the reasonable quantitative estimates of temperature dependent bandgap shifts, optical absorption and photovoltaic properties of p-n heterojunctions.

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“…According to Qin et al [6] reduced graphene oxides (rGO) have a tendency to restrict the agglomeration of nanoparticles to increase the number of effective active reaction sites which accelerate the charge transfer process during degradation. Apart from this, Natarajan et al [16] explained that adding carbon compounds to ZnS can make them more responsive to both UV-visible and visible wavelengths by slowing down the rate of excitonic recombination. Up to now, the photocatalytic properties of ZnS-rGO nanohybrids prepared by two-step chemical synthesis, one-pot synthesis method, hydrothermal method, solvothermal method, UV-assisted synthesis method, green method, microwave-aided synthesis method, one-step solvothermal method, one-pot hydrothermal method, and widely recognized solid-state reactions have been reported [5,6,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32].…”

Section: Introductionmentioning

confidence: 99%

“…Apart from this, Natarajan et al [16] explained that adding carbon compounds to ZnS can make them more responsive to both UV-visible and visible wavelengths by slowing down the rate of excitonic recombination. Up to now, the photocatalytic properties of ZnS-rGO nanohybrids prepared by two-step chemical synthesis, one-pot synthesis method, hydrothermal method, solvothermal method, UV-assisted synthesis method, green method, microwave-aided synthesis method, one-step solvothermal method, one-pot hydrothermal method, and widely recognized solid-state reactions have been reported [5,6,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32]. In most cases, the synthesis process is complicated, temperaturedependent, and time-consuming.…”

Section: Introductionmentioning

confidence: 99%

Enhanced photocatalytic efficiency of sol-gel derived ZnS-rGO binary nanocomposite

Kumari,

Sharma,

Mishra

et al. 2024

Phys. Scr.

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A facile chemical route of synthesis of ZnS-rGO binary nanocomposites is reported here. The efficacy of such nanocomposites as a photocatalyst in degrading the common pollutant dye such as Methylene blue (MB), has been thoroughly investigated and the underlying mechanism is also presented. The standard characterization methods were applied to understand the structure, bonding, morphology, optical and elemental compositions. The results indicated that the ZnS nanoparticles were well dispersed into the rGO nanosheets which due to their 2-D sheet structure, served as a favourable template for growth and control of morphology. Increase in rGO amount showed a direct impact on particle size confirmed by XRD and Raman both. The synthesized nanocomposites were utilized as photocatalyst for the degradation of MB dyes under UV irradiation. The optimal combination of ZnS and rGO (in the ratio of 3:2) exhibited enhanced photocatalytic activity. A higher rate constant of 7.01×10−3 min−1, and an approximate degradation efficiency of 75% were obtained after 90 mins of degradation. The improvement in photocatalytic activity can be attributed to the enhancement in charge separation, suppressed recombination of electron-hole (e-–h+) carriers, and a possible longer electron lifetime due to the presence of higher amount of rGO. Here, rGO assisted the suppression of charge recombination process in ZnS-rGO and ignited hydroxyl radicals and super-oxide ions which further accelerated the degradation rate of dye. Based on the nature of the dye and its concentration, a significant amount of rGO was needed to maximize the photocatalytic efficiency of ZnS-rGO binary nanocomposites. In addition, the dark current variation with applied bias was explored and it depicted a reduction in dark current with optimized amount of rGO in nanocomposite. The nanocomposites have a strong potential to be utilized in water purification and nano-detectors.

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Effect of electron-phonon interaction and valence band edge shift for carrier-type reversal in layered ZnS/rGO nanocomposites

Cited by 15 publications

References 43 publications

Hybrid Reduced Graphene Oxide/GaN Nanocolumns on Flexible Niobium Foils for Efficient Photoelectrochemical Water Splitting

Hybrid Reduced Graphene Oxide/GaN Nanocolumns on Flexible Niobium Foils for Efficient Photoelectrochemical Water Splitting

Influence of temperature on bandgap shifts, optical properties and photovoltaic parameters of GaAs/AlAs and GaAs/AlSb p–n heterojunctions: insights from ab-initio DFT + NEGF studies

Enhanced photocatalytic efficiency of sol-gel derived ZnS-rGO binary nanocomposite

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