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Exploring optical properties of Gd doped zincblende GaN for novel optoelectronic applications (A DFT+U study)
摘要： In current research, we investigate optical properties of Gd doped zincblende GaN using Wien2K code, by employing DFT+U. We consider pure GaN and we dope various Gd concentrations 3.12%, 6.25% and 12.5% into the host GaN lattice while supercell size is kept fixed (1×2×2) for all cases. We elaborate and present a detailed comparison among optical and electronic properties of pure GaN with various Gd concentrations. Interaction of Gd and N atoms and localization of d and f states of dopant are remarked near Fermi level or maxima of valence band. In comparison to pure GaN, absorption spectra for 3.12% Gd concentration shows redshift but for highest Gd concentration (6.25% 12.5%), a blueshift in absorption spectrum is noted. Absorption is pronounced and enhanced in the UV region. Study of optical spectra for various optical properties suggest that Gd:GaN system is mostly suitable for UV optoelectronics. Results for optical properties have great similarity with the existing literature works. Our unprecedented and first ever reported results on optical properties of Gd:GaN system, direct future path of this material for its potential uses in UV optoelectronic, photonic, LEDs, UV sterilization application, photosensors, thermochromic solar cells and biochemical sensing industries.
关键词： optical properties,density of states,DFT calculations,gallium nitride (GaN),Gd doping
更新于2025-09-23 15:19:57
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Computational DFT calculations, photovoltaic properties and synthesis of (2R, 3S)-2, 3, 4-trihydroxybutoxy substituted phthalocyanines
摘要： In this study, 4-((2R, 3S)-2, 3, 4-trihydroxybutoxy) phthalonitrile was synthesized and characterized as starting material. This new starting material reacts with cobalt and copper metal salts to obtain metallophthalocyanine complexes. The electronic absorption of cobalt and copper phthalocyanine compounds in different concentrations of THF was investigated. In addition, the solubility and absorption of the compounds in different solvents were investigated. Density functional theory was also performed to support the relevant experimental results of the synthesized copper and cobalt center atomic compound. The photovoltaic performance of compounds was measured as current density–voltage (J–V).
关键词： DFT calculations,aggregation,photovoltaic,synthesis,Phthalocyanine
更新于2025-09-23 15:19:57
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First Principle Study of Optical Properties of Cu doped zincblende GaN for Novel Optoelectronic Applications
摘要： Current computational study is focused on calculation of optical properties of Cu doped zincblende GaN system where PBE-GGA approximation is employed in Wien2K code. We consider various Cu concentrations 6.25%, 3.12%, 1.56% corresponding to 1× 1 × 2, 1 × 2 × 2, 2 × 2 × 2 supercell configurations respectively. We substitute one Ga atom with one Cu atom in each concentration and we present a good comparison among optical properties of pure GaN and all Cu concentrations. TDOS and PDOS plots reveal contribution of Ga p-states, N p-states and Cu d-states. Optical absorption shows redshift in comparison to pure GaN and because of interactions of Cu and N atoms, we inspect localized d-states at minima of conduction band or Fermi level. Hence, electro-optical properties of zincblende GaN are enhanced upon addition of impurity (Cu) and the material may potentially be used in photonic, power electronics, solar cells, optoelectronics, UV photodetectors and LEDs.
关键词： Gallium Nitride,DFT calculation,Cu doping,Optical Properties,Density of states
更新于2025-09-23 15:19:57
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Layer-dependent signatures for exciton dynamics in monolayer and multilayer WSe2 revealed by fluorescence lifetime imaging measurement
摘要： Two-dimensional (2D) transition-metal dichalcogenide (TMD) materials have aroused noticeable interest due to their distinguished electronic and optical properties. However, little is known about their complex exciton properties together with the exciton dynamics process which have been expected to influence the performance of optoelectronic devices. The process of fluorescence can well reveal the process of exciton transition after excitation. In this work, the room-temperature layer-dependent exciton dynamics properties in layered WSe2 are investigated by the fluorescence lifetime imaging microscopy (FLIM) for the first time. This paper focuses on two mainly kinds of excitons including the direct transition neutral excitons and trions. Compared with the lifetime of neutral excitons (< 0.3 ns within four-layer), trions possess a longer lifetime (~ 6.6 ns within four-layer) which increases with the number of layers. We attribute the longer-lived lifetime to the increasing number of trions as well as the varieties of trion configurations in thicker WSe2. Besides, the whole average lifetime increases over 10% when WSe2 flakes added up from monolayer to four-layer. This paper provides a novel tuneable layer-dependent method to control the exciton dynamics process and finds a relatively longer transition lifetime of trions at room temperature, enabling to investigate in the charge transport in TMD-based optoelectronics devices in the future.
关键词： two-dimensional (2D) WSe2,fluorescence lifetime,fluorescence lifetime imaging microscopy (FLIM),exciton dynamics,density functional theory (DFT)
更新于2025-09-23 15:19:57
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Realizing Synergistic Effect of Electronic Modulation and Nanostructure Engineering over Graphitic Carbon Nitride for Highly Efficient Visible-Light H2 Production Coupled with Benzyl Alcohol Oxidation
摘要： Photocatalytic H2 production based on g-C3N4 faces enormous challenging issues including limited visible-light absorption, poor separation and transfer abilities of photo-generated electron-hole pairs. Herein, we realize the synergistic effect of nanostructure engineering and electronic modulation with a supramolecular assembly mediated synthesis of heteroatom doped g-C3N4 hierarchical mesoporous spheres. The favorable doping site and possible effect on electronic structure are disclosed by DFT calculation with supporting experimental analysis. Impressively, S-doped g-C3N4 delivers a 13.2 times higher H2 production rate than bulk g-C3N4 under visible-light. More importantly, as the dual functional photocatalyst for H2 production and selective oxidation of benzyl alcohol, it can exhibit outstanding activity with a H2/benzaldehyde production rate of 3.76/3.87 μmol h-1, respectively. This work not only provide a new rationale for photocatalytic performance enhancement, but also shed new light on the highly efficient utilization of solar energy by coupling H2 generation with value added chemical production.
关键词： graphitic carbon nitride,hierarchical mesoporous spheres,DFT calculation,benzyl alcohol oxidation,photocatalytic hydrogen production
更新于2025-09-23 15:19:57
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Photovoltaic cells with various azo dyes as components of the active layer
摘要： The photovoltaic response of six cells with an active layer of heterocyclic azo dyes is presented for the first time. The active azo layers differed in the type of substituent (i.e. electron-donating: CH3, OCH3 and electron withdrawing: Br). We showed that by changing the substituent in the heterocyclic azo dye we change the power efficiency of the device. It should be mentioned that all presented data showed high potential of heterocyclic azo dyes for effective photovoltaic output. The studied heterocyclic azo dyes have higher photovoltaic parameters than those obtained for photovoltaic cell with 4-Diethoxyphenylsilylazobenzene.
关键词： Theoretical DFT calculations,Photovoltaic cell,Thin films,Heterocyclic azo dyes,Current density-voltage characteristics
更新于2025-09-23 15:19:57
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A DFT study to probe homo-conjugated norbornylogous bridged spacers in dye-sensitized solar cells: an approach to suppressing agglomeration of dye molecules
摘要： This work reports a sigma-bridged framework as spacers to design new dye-sensitized solar cells. The norbornylogous bridged spacer can avoid p–p aggregation of dye molecules on the semiconductor surface in DSSCs. These sesquinorbornatrienes are known to exhibit electron propagation through the interaction of sigma and p orbitals via through bond (OITB) and through space (OITS) mechanisms. Density functional theory (DFT) calculations performed with these spacers and a modelled simple donor unit like N,N-dimethylamine and cyanoacrylic acid as the anchoring group showed significant results with the requisite optical parameters for DSSCs. The newly designed dyes have shown comparable or better optical properties compared to the reference dye molecule with p-conjugated thiophene spacer units. The DGinjection, VOC and mnormal values calculated for the designed dyes were found to be higher than those of the reference system. The trans-sesquinorbornatriene system spacer (6-D) showed a VOC of 3.3 eV, DGinjection of 2.4 eV and oscillatory strength (f) of 0.96. The total and partial density of states indicates a good communication between the valence and conduction band for the designed dyes. Transition density matrix results suggest that the exciton dissociation in the excited state is sufficiently high to overcome the coulombic attraction of the hole. These results are promising for the design of dye molecules with such scaffolds, to achieve better efficiency and to eliminate one of the major issues with p-spacer units in DSSCs.
关键词： homo-conjugated norbornylogous bridged spacers,dye molecules,DFT study,dye-sensitized solar cells,suppressing agglomeration
更新于2025-09-23 15:19:57
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Symmetry controlled photo-selection and charge separation in butadiyne-bridged donora??bridgea??acceptor compounds
摘要： Electron transfer (ET) in donor-bridge-acceptor (DBA) compounds depends strongly on the structural and electronic properties of the bridge. Among the bridges that support donor - acceptor conjugation, alkyne bridges have attractive and unique properties: they are compact, possess linear structure permitting access to high symmetry DBA structures, and allow torsional motion of D and A, especially for longer bridges. We report conformation dependent electron transfer dynamics in a set of novel DBA compounds featuring butadiyne (C4) bridge, N-isopropyl-1,8-napthalimide (NAP) acceptors, and donors that span a range of reduction potentials (trimethyl silane (Si-C4-NAP), phenyl (Ph-C4-NAP), and dimethyl aniline (D-C4-NAP)). Transient mid-IR absorption spectra of the C≡C bridge stretching modes, transient spectra in the visible range and TD-DFT calculations were used to decipher the ET mechanisms. We found that the electronic excited state energies and, especially, the transition dipoles (S0→Sn) depend strongly on the dihedral angle (θ) between D and A and the frontier orbital symmetry, offering an opportunity to photo-select particular excited states with specific ranges of dihedral angles by exciting at chosen wavelengths. For example, excitation of D-C4-NAP at 400 nm predominantly prepares an S1 excited state in the planar conformations (θ ~ 0) but selects an S2 state with θ ~ 90o, indicating the dominant role of the molecular symmetry in the photophysics. Moreover, the symmetry of the frontier orbitals of such DBA compounds not only defines the photo-selection outcome, but also determines the rate of the S2→S1 charge separation reaction. Unprecedented variation of the S2-S1 electronic coupling with θ by over four orders of magnitude results in slow ET at θ ca. 0o and 90o but extremely fast ET at θ of 20-60o. The unique features of high-symmetry alkyne bridged DBA structures enable frequency dependent ET rate selection and make this family of compounds promising targets for the vibrational excitation control of ET kinetics.
关键词： transient absorption spectroscopy,electron transfer,donor-bridge-acceptor,TD-DFT calculations,butadiyne bridge
更新于2025-09-23 15:19:57
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Structure and Conformation of a Crystalline P3HT Film Adsorbed on an Alkanethiol Self-Assembled Monolayer Deposited on Gold
摘要： All-atom molecular dynamics simulations are performed to investigate the structural and conformational properties of a regioregular poly(3-hexylthiophene) (P3HT) crystal in the presence of a gold (Au) substrate terminated with an n-alkanethiol self-assembled monolayer (SAM). The employed orientation of the P3HT crystals deposited on the SAM is the edge-on, since this orientation is believed to be the most energetically favorable and stable, also yielding the highest charge carrier mobility in organic thin-film transistors. The unit cell of the overall Au/SAM interfacial layer is obtained through detailed ab initio calculations. Systems with a varying number of P3HT stacks on the Au/SAM substrate are studied with an all-atom force field in order to elucidate the effect of polymer thickness on the structural properties of the system. All final structures are found to be stable and well-equilibrated. Insights into the P3HT crystal structure are provided for the P3HT layers in direct contact with the SAM, but also for those deeper in the polymer film. According to the simulations, the majority of conformational and packing properties of the P3HT film are practically similar to those of the bulk crystalline P3HT material, implying that its structure remains unaffected by the presence of the underlying Au/SAM substrate.
关键词： DFT calculations,semiconducting polymers,molecular dynamics simulations,self-assembled monolayers,P3HT
更新于2025-09-23 15:19:57
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Theoretical investigation using DFT of quinoxaline derivatives for electronic and photovoltaic effects
摘要： Photovoltaic properties of solar cells based on fifteen organic dyes have been studied in this work. B3LYP/6-311G (d,p) methods are realized to obtain geometries and optimize the electronic properties, optical and photovoltaic parameters for some quinoxaline derivatives. The results showed that time dependent DFT investigations using the CAM-B3LYP method with the polarized split-valence 6-311G (d,p) basis sets and the polarizable continuum model PCM model were sensibly able to predict the excitation energies, the spectroscopy of the compounds. HOMO and LUMO energy levels of these molecules can make a positive impact on the process of electron injection and dye regeneration. Gaps energy ΔEg, short-circuit current density Jsc, light-harvesting efficiency LHE, injection driving force ΔGinject, total reorganization energy λtotal and open-circuit photovoltage Voc enable qualitative predictions about the reactivity of these dyes.
关键词： Computing methodology,TD-DFT,Energy,PCM,Optoelectronic,Particle physics,Quantum mechanics,Photovoltaic,Physics,Quinoxaline derivatives,Theoretical computer science,Solar cells,Molecular physics
更新于2025-09-23 15:19:57