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Co-doping metal oxide nanotubes: superlinear photoresponse and multianalyte sensing
摘要： Metal oxide nanotubes and standalone membranes have been extensively researched for potential applications ranging from electronics, optoelectronics, and photocatalysis, to ?ltration and gas sensing. Although the wide-bandgap of these nanotubes poses challenges for their utilization for photochemical conversion and charge transport, doped metal-oxide nanotubes provide an alternative to lower their bandgap and provide charge carriers for conduction and photochemistry. While many single-dopants have been successfully used, co-dopants can be used to manipulate the electronic density of states, photophysical and photochemical properties to obtain new and unexpected functionalities, sometimes even completely different from the individual dopants. Here the co-doped titanium dioxide (TiO2) nanotube membranes are described where the combined properties of the co-dopants differ from their monodoped counterparts. A detailed mechanistic model is provided to explain the new photophysical and photochemical properties of these co-doped metal oxide membranes, and novel functionalities resulting from such properties like superlinear photoresponse and enhanced gas sensing response. In addition, the potential applications of these functionalities are shown in photodetection and multianalyte sensing as portable devices.
关键词： electronic properties,multianalyte sensors,metal-oxide nanotubes,co-doping,photophysics
更新于2025-09-19 17:13:59
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DFT coupled with NEGF study of the electronic properties and ballistic transport performances of 2D SbSiTe <sub/>3</sub>
摘要： Identifying novel 2D semiconductors with promisingly electronic properties and transport performances for the development of electronic and optoelectric applications is of utmost importance. Here, we show a detailed study of the electronic properties and ballistic quantum transport performance of a new 2D semiconductor, SbSiTe3, based on density functional theory (DFT) and non-equilibrium Green formalism. Promisingly, monolayer SbSiTe3 owns an indirect band gap of 1.61 eV with a light electron effective mass (0.13 m0) and an anisotropic hole effective mass (0.49 m0 & 1.34 m0). The ballistic performance simulations indicate that the 10-nm monolayer SbSiTe3 n- and p-MOSFETs display a steep subthreshold swing of about 80 mV/dec and a high on/off ratio (106), which indicates a good gate controlling capacibility. As the channel length of SbSiTe3 decreases to 5 nm, its p-MOSFET can also effectively suppress the intra-band tunneling. Therefore, 2D SbSiTe3 is a potential semiconductor for the future nano electronics.
关键词： electronic properties,MOSFET,SbSiTe3,2D semiconductor,ballistic transport
更新于2025-09-19 17:13:59
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Molecular designing of naphthalene diimide based fullerene-free small organic solar cell - Acceptors with high photovoltaic performance by density functional theory
摘要： With the help of computational chemistry tools, three non-fullerene acceptors, which are 2-methylene-malononitrile (M-1), 2-(3-methyl-5-methylene-2-thioxothiazolidin-4-ylidene) malononitrile (M-2) and 1-methyl-5-methylene-2,6-dioxo-1,2,5,6-tetrahydropyridine-3-carbonitrile (M-3), are designed with naphthalene diimide (NDI) central unit. Their different photovoltaic and optoelectronic properties like absorption spectrum, electrons density, solubility strength, reorganization energies, % ETC from donor to acceptor part, excitation energies, oscillating strength, morphology and crystallinity of device for constructing the thin film bulk hetro junction devices were computed at the WB97XD/6-31 G (d, p) level of density functional theory (DFT). Expected open circuit voltages of designed molecules are high as 4.05 eV to 4.49 eV, which are significantly larger than that of the previously reported 3-methyl-5-methylene-2-thioxothiazolidin-4-one (R) with the value of 3.60 eV at the zero current level. Charge carrier mobilities of designed molecules are high due to having low re-organization energies varying from 0.0163 eV to 0.0280 eV for electron and 0.0160 eV to 0.0190 eV for hole, strong absorption properties between the 420 nm to 550 nm in chloroform and 400 nm to 540 nm in gas phase conditions, respectively.
关键词： opto-electronic properties,non-fullerene acceptors,theoretical calculations,dipole moment,organic solar cells,naphthalene di-imide
更新于2025-09-19 17:13:59
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Size-controlled excitonic effects on electronic and optical properties of Sb <sub/>2</sub> S <sub/>3</sub> nanowires
摘要： In this work, the electronic and optical properties of one-dimensional (1D) Sb2S3 nanowires (NWs) with different sizes are investigated using first-principles calculations. The indirect–direct band transition of Sb2S3 NWs can be tuned effectively by the NW size and various uniaxial strains. In the Sb2S3 NWs, the quantum confinement effects result in wider bandgaps while the significantly enhanced electron–hole interaction that is expected to produce excitonic bound states generates a bandgap narrowing. The exciton binding energies for the Sb2S3 NWs are predicted by the effective masses of electrons and holes to lie in the range of 0–1 eV, which are larger than that of bulk Sb2S3, suggesting that excitons in Sb2S3 NWs may bind possible defects to promote luminescence. The size-controlled absorption edge blueshift and redshift of Sb2S3 NWs suggest that Sb2S3 NWs may be promising in the applications of nanoscale light emitting devices.
关键词： optical properties,first-principles calculations,quantum confinement effects,light emitting devices,electronic properties,exciton binding energies,Sb2S3 nanowires
更新于2025-09-16 10:30:52
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Effect of mixed halide contents on structural, electronic, optical and elastic properties of CsSnI <sub/>3a??x</sub> Br <sub/>x</sub> for solar cell applications: first-principles study
摘要： In this study, structural, electronic, optical and elastic properties of CsSnI3?xBrx perovskites are investigated by full potential linearized augmented plane wave method (FP-LAPW) with exchange correlation functionals GGA-PBE and GGA-mBJ as implemented in Wien2k. The calculated structural parameters for all compositions are in good correlation with literature. The band structures and density of states (DOS) are calculated by GGA which indicated that all these alloys have direct band gap. Furthermore, the band gaps are also calculated by employing modified Beck-Johnson’s (mBJ) exchange potential. The obtained band gaps with this method are found to be improved as compared to GGA. The calculated optical parameters show that these materials have the competency for light absorption and to retain it. These characteristics make them promising materials for solar cell applications. The elastic constants have also been calculated which revealed that all these compounds have ductile nature. The mixed halide contents are pioneered in this study and therefore, no data is in hand for estimation.
关键词： optical and elastic properties,electronic properties,lead free perovskites,halide contents,modified beck and johnson (mbj) exchange potential
更新于2025-09-16 10:30:52
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Electro-Optical Properties of Monolayer and Bilayer Pentagonal BN: First Principles Study
摘要： Two-dimensional hexagonal boron nitride (hBN) is an insulator with polar covalent B-N bonds. Monolayer and bilayer pentagonal BN emerge as an optoelectronic material, which can be used in photo-based devices such as photodetectors and photocatalysis. Herein, we implement spin polarized electron density calculations to extract electronic/optical properties of mono- and bilayer pentagonal BN structures, labeled as B2N4, B3N3, and B4N2. Unlike the insulating hBN, the pentagonal BN exhibits metallic or semiconducting behavior, depending on the detailed pentagonal structures. The origin of the metallicity is attributed to the delocalized boron (B) 2p electrons, which has been veri?ed by electron localized function and electronic band structure as well as density of states. Interestingly, all 3D networks of different bilayer pentagonal BN are dynamically stable unlike 2D structures, whose monolayer B4N2 is unstable. These 3D materials retain their metallic and semiconductor nature. Our ?ndings of the optical properties indicate that pentagonal BN has a visible absorption peak that is suitable for photovoltaic application. Metallic behavior of pentagonal BN has a particular potential for thin-?lm based devices and nanomaterial engineering.
关键词： optical properties,electronic properties,metallic behavior,mono/bilayer pentagonal BN
更新于2025-09-16 10:30:52
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Graphene Photonics || Electronic Properties
摘要： The ?ow of free charge carriers, i.e., electrons in the conduction band or holes in the valence band, in a semiconductor that is subject to an electric ?eld is accelerated by the electric field but is hindered by scattering events. In a semiconductor, free carriers accelerate in the presence of an electric field. The randomly distributed scattering centers, such as impurities and defects, act as a counter force that decelerates and de?ects the carriers. When the steady state is eventually reached under a constant electric field, a constant ?ow of carriers is achieved. In graphene, by contrast, charge carriers on the Dirac cone have a constant speed and do not accelerate or decelerate in response to the electric field or the scattering centers; instead, the effect of the electric field is rather to align the motion of carriers to the direction of the electric field, and the scattering centers act as a source to disturb this alignment process. This process is well captured by the Boltzmann transport equation, which has successfully described many statistical behaviors of carriers in metals and semiconductors. The purpose of this chapter is to describe the electronic properties of graphene, starting from the Boltzmann transport equation.
关键词： Boltzmann transport equation,charge carriers,electric field,electronic properties,conductivity,scattering events,graphene,two-dimensional material
更新于2025-09-16 10:30:52
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Photophysical and electronic properties of bismuth-perovskite shelled lead sulfide quantum dots
摘要： Metal halide perovskite shelled quantum dot solids have recently emerged as an interesting class of solution-processable materials that possess the desirable electronic properties of both quantum dots and perovskites. Recent reports have shown that lead sulfide quantum dots (PbS QDs) with perovskite ligand-shells can be successfully utilized in (opto)electronic devices such as solar cells, photoconductors, and field-effect transistors (FETs), a development attributed to the compatibility of lattice parameters between PbS and certain metal halide perovskites that results in the growth of the perovskite shell on the PbS QDs. Of several possible perovskite combinations used with PbS QDs, bismuth-based variants have been shown to have the lowest lattice mismatch and to display excellent performance in photoconductors. However, they also display photoluminescence (PL), which is highly sensitive to surface defects. In this work, we present an investigation of the transport and optical properties of two types of bismuth-based perovskite (MA3BiI6 and MA3Bi2I9) shelled PbS QDs. Our photophysical study using temperature-dependent PL spectroscopy between 5 and 290 K indicates that the PL efficiency of the reference oleic acid (OA) capped samples is much higher than that of the Bi-shelled ones, which suffer from traps, most likely formed at their surfaces during the phase-transfer ligand exchange process. Nevertheless, the results from electrical measurements on FETs show the successful removal of the native-OA ligands, displaying electron dominated transport with modest mobilities of around 10?3 cm2 [V s]?1 – comparable to the reported values for epitaxial Pb-based shelled samples. These findings advance our understanding of perovskite shelled QD-solids and point to the utility of these Bi-based variants as contenders for photovoltaic and other optoelectronic applications.
关键词： field-effect transistors,bismuth-perovskite,electronic properties,photoluminescence,photophysical properties,lead sulfide quantum dots
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019 - Kerala, India (12–14 June 2019)] PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019 - A review on computational modelling of individual device components and interfaces of perovskite solar cells using DFT
摘要： Perovskite structures with the same crystal structure as CaTiO3, are of importance in the field of Materials Science right from the discovery of ceramic high-temperature superconductors to the organic–inorganic semiconductors for high-efficiency photovoltaics. Owing to their unique crystal structure, perovskites display a variety of interesting properties like ferroelectricity, superconductivity, magnetoresistance, birefringence, piezoelectricity etc. Moreover, the efficiency of perovskite solar cells has increased from 3.1% in 2009 to 22.1% in 2017. Since a large number of elements can be combined to form perovskite structures, one can selectively design and optimize perovskite’s physical, optical and electrical characteristics. Through theoretical and computational modelling, it is possible to access the hitherto unknown atomistic properties, opto-electronic properties and operational mechanisms of these materials with high accuracy. This paper aims at explaining some of the potentialities of DFT hybrid functionals to analyze the electronic, structural and optical properties of compounds constituting various layers of a perovskite solar cell with the help of software packages like VASP, Wien 2k. Gaussian 09 etc. This paper also reviews the effect of doping on the electronic properties of various layers of perovskite solar cells including the band gap, visible light absorption, relaxation time of holes and electrons using DFT, which in turn determines the optimum charge separation. The effect of introduction of an Intermediate Band Gap in the perovskite structure using DFT methods based on G0W0+SOC approach is also discussed here. A study on the effect of various intrinsic defects present in perovskite structures using DFT calculations with VASP package is also discussed. The relevance of modelling the interfaces of various layers of perovskite solar cells with DFT packages is discussed with the help of selected examples of materials and representative interfaces.
关键词： optical properties,DFT,computational modelling,electronic properties,interfaces,Perovskite solar cells
更新于2025-09-12 10:27:22
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The influence of edge structure on the optoelectronic properties of Si <sub/>2</sub> BN quantum dot
摘要： In recent work, we have investigated the electronic and optical properties of pristine and functionalized Si2BN quantum dots (QDs) using first-principles calculations. Due to the edge functionalization, Si2BN QDs have binding energies of ?0.96 eV and ?2.08 eV per hydrogen atom for the adsorption of single and double hydrogen atoms, respectively. These results reveal the stability and the bonding nature of hydrogen at the edges of Si2BN QD. In particular, the charge transfer between hydrogen and other atoms is explicitly increased. The electronic band structure of pristine Si2BN QD shows a metallic behavior with a finite number of electronic states in the density of states at the Fermi level. The frequency-dependent optical properties, such as refractive index, extinction coefficient, absorption coefficient, electron energy loss spectra, and reflectivity, are computed for both the parallel and perpendicular components of electric field polarization. The higher absorption was found in the infrared regime. The present study shows that the functionalization of Si2BN QD by two hydrogen atoms is energetically stable. It offers a promising application of Si2BN QD, which can be used in optical nanodevices such as photodetectors and biomedical imagination.
关键词： optical properties,Si2BN quantum dot,first-principles calculations,metallic behavior,electronic properties,hydrogen functionalization,infrared absorption,optical nanodevices
更新于2025-09-12 10:27:22