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Discussion on growth, emission and piezoelectric properties of zinc guanidinium phosphate single crystal: a potential candidate for transducer and LED applications
摘要： Zinc guanidinium phosphate, a semi-organic single crystal, was grown successfully by a slow evaporation solution growth technique. The cell parameters of the grown crystal were con?rmed using a powder X-ray diffraction study. The electrical property of the sample was analysed using dielectric and piezoelectric studies. The dielectric constant, dielectric loss and alternating-current conductivity were calculated for various frequencies and temperatures. The solid state parameters such as plasma energy, Penn gap energy, Fermi energy and electronic polarizability were calculated. The piezoelectric property of the title crystal was ascertained by determining its piezoelectric charge coef?cient (d33). The optical transmittance and energy gap of the grown crystal were examined using ultraviolet–visible–near-infrared spectral analysis. The title molecule was optimized and the frontier molecular orbital was performed using B3LYP/6-31 + G(2d,2p). The emission property of the titular compound was analysed using a photoluminescence study. The dominant colour emission of the grown crystal was found using CIE colour chromaticity coordinates. The nonlinear property of the titular compound was con?rmed using a Kurtz–Perry powder technique. The above results illustrate that the title crystal is a potential candidate for light emitting and nonlinear applications. This work explains the dominant colour emitting behaviour and electrical properties such as dielectric and piezoelectric properties of the title crystal, which are reported for the ?rst time.
关键词： piezoelectric,Semi-organic crystal,photoluminescence,Penn gap energy,HOMO–LUMO
更新于2025-09-12 10:27:22
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Designing dithienonaphthalene based acceptor materials with promising photovoltaic parameters for organic solar cells
摘要： Scientists are focusing on non-fullerene based acceptors due to their efficient photovoltaic properties. Here, we have designed four novel dithienonaphthalene based acceptors with better photovoltaic properties through structural modification of a well-known experimentally synthesized reference compound R. The newly designed molecules have a dithienonaphthalene core attached with different 2-(5,6-difluoro-2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)malononitrile (H1), 2-(5,6-dicyano-2-methylene-3-oxo-2,3-dihydroinden-1-ylidene)-malononitrile (H2), 2-(5-methylene-6-oxo-5,6-dihydrocylopenta[c]thiophe-4-ylidene)-malononitrile (H3) and 2-(3-(dicyanomethylene)-2,3-dihydroinden-1-yliden)malononitrile (H4) acceptor moieties (end-capped). The photovoltaic parameters of the designed molecules are discussed in comparison with those of the reference R. All newly designed molecules show a reduced HOMO–LUMO energy gap (2.17 eV to 2.28 eV), compared to the reference R (2.31 eV). Charger transfer from donor to acceptor is confirmed by a frontier molecular orbital (FMO) diagram. All studied molecules show extensive absorption in the visible region and absorption maxima are red-shifted compared to R. All investigated molecules have lower excitation energies which reveal high charge transfer rates, as compared to R. To evaluate the open circuit voltage, the designed acceptor molecules are blended with a well-known donor PBDB-T. The molecule H3 has the highest Voc value (1.88 V). TDM has been performed to show the behaviour of electronic excitation processes and electron hole location between the donor and acceptor unit. The binding energies of all molecules are lower than that of R. The lowest is calculated for H3 (0.24 eV) which reflects the highest charge transfer. The reorganization energy value for both the electrons and holes of H2 is lower than R which is indicative of the highest charge transfer rate.
关键词： absorption maxima,binding energies,reorganization energy,photovoltaic properties,open circuit voltage,charge transfer,dithienonaphthalene,HOMO–LUMO energy gap,non-fullerene based acceptors
更新于2025-09-12 10:27:22
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Revealing the Critical Role of the HOMO Alignment on Maximizing Current Extraction and Suppressing Energy Loss in Organic Solar Cells
摘要： For state-of-the-art organic solar cells (OSCs) consisting of a large-bandgap polymer donor and a near-infrared (NIR) molecular acceptor, the control of the HOMO offset is the key to simultaneously achieve small energy loss (Eloss) and high photocurrent. However, the relationship between HOMO offsets and the efficiency for hole separation is quite elusive so far, which requires a comprehensive understanding on how small the driving force can effectively perform the charge separation while obtaining a high photovoltage to ensure high OSC performance. By designing a new family of ZITI-X NIR acceptors (X = S, C, N) with a high structural similarity and matching them with polymer donor J71 forming reduced HOMO offsets, we systematically investigated and established the relationship among the photovoltaic performance, energy loss, and hole-transfer kinetics. We achieved the highest PCEavgs of 14.05 G 0.21% in a ternary system (J71:ZITI-C:ZITI-N) that best optimize the balance between driving force and energy loss.
关键词： HOMO alignment,energy loss,ZITI-X NIR acceptors,organic solar cells,current extraction
更新于2025-09-11 14:15:04
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Photonic enhancement of parallel homo-tandem solar cells through the central electrode
摘要： Improvement of solar cell performance through the parallel homo-tandem architecture is studied. The cell geometry is optically designed to maximize absorption of the AM1.5 spectrum. We consider both ITO electrode and a recently devised ITO-free alternative, the Two-Resonance Tapping Cavity. The optimal geometry strongly depends on this choice. We identify two mechanisms by which tandem cells outperform single cells: (i) back-up absorption and (ii) interferometric gain mediated by the central metallic electrode. We numerically demonstrate large improvement in short-circuit current for a wide choice of realistic materials: PTB7-th:PC71BM, P3HT:PC61BM, DBP:C70, and methylammonium lead halide perovskite, as well as a theoretical material with a Shockley-Queiser type of spectral absorption plus an Urbach tail. Such an idealized response is found to reliably model real materials. A general response pattern is found that fits all the cases covered in our study, and which can serve as a guide to optimize homo-tandem cells.
关键词： Homo-tandem solar cells,ITO,TRTC,Photon management,Micro-cavity
更新于2025-09-11 14:15:04
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Distortion‐Controlled Red‐Shift of Organic Dye Molecules
摘要： We show quantum chemically how structural distortion of an aromatic dye molecule can be leveraged to rationally tune its optoelectronic properties. Using a quantitative Kohn-Sham MO approach in combination with Time-Dependent DFT (TD-DFT), we have investigated the influence of various structural and electronic tuning parameters on the HOMO–LUMO gap of a benzenoid model dye, amongst others: (i) out-of-plane bending of the aromatic core; (ii) bending of the bridge with respect to the core; (iii) the nature of the bridge itself; and (iv) π-π stacking. Our study reveals the coupling of multiple structural distortions as a function of bridge length and number of bridges in benzene to be chiefly responsible for a decreased HOMO–LUMO gap and consequently the red-shifting of the absorption wavelength associated with the lowest singlet excitation (ca. 560 nm) in our model cyclophane systems. These physical insights together with a rational approach for tuning the oscillator strength were leveraged for the proof-of-concept design of the intense near-infrared (NIR) absorbing cyclophane dye 18 at 785 nm. Our design may contribute to a new class of distortion-controlled NIR absorbing organic dye molecules.
关键词： Cyclophane,NIR Absorption,Structural Distortion,HOMO–LUMO gap,Time-Dependent DFT
更新于2025-09-11 14:15:04
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Synthesis, spectral characterization (FT-IR and NMR) and DFT (Conformational analysis, molecular structure, HOMO-LUMO, UV-vis, NLO) computational studies on 2,2’-((1E,1’E)-phenazine-2,3 dilbis(azanylylidene))bis(methanyly- lidene))diphenol
摘要： A new Schiff base was synthesized for the first time by the phenazine-2,3-diamine and 2-hydroxy benzaldedye in ethanol (1:1). The structure of Schiff bases was experimentally characterized by using UV-vis, IR, 1H NMR and 13C NMR spectroscopic methods. Further, the synthesized compound was subjected to DFT for better understanding of the molecular architecture and optoelectronic properties. The optimized geometric parameters supported the available experimental values. The Mulliken and MEP analyses are utilized to identify reactive sites of title molecule. The energetic behaviors of compound 3 in hexane, chloroform, methanol solvents and gas phase were examined using by time-dependent DFT (TD-DFT) method by applying the polarizable continuum model (PCM). The calculated ΔE energies exposed that charge transfer takes place within the molecule. In addition to the polarizability and hyperpolarizability have been calculated which exhibit that compounds possess non-linear optical nature.
关键词： Schiff Base,MEP,HOMO-LUMO,DFT,Mulliken Charge
更新于2025-09-10 09:29:36
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Spectroscopic Investigation (FT-IR, FT-Raman, NMR and UV-Vis),Conformational Stability, NBO and Thermodynamic Analysis of 1-(2-Methoxyphenyl) Piperazine and 1-(2-Chlorophenyl) Piperazine by DFT Approach
摘要： The Vibrational and electronic properties of phenyl substituted compounds 1-(2-methoxyphenyl)piperazine and 1-(2-chlorophenyl)piperazine have been investigated by FT-IR, FT-Raman, NMR and UV-Vis spectral measurements. Density functional theory (DFT) method, using B3LYP functional, with 6-311++G (d,p) basis set, has been performed for assigning vibrational frequencies of the title compounds, which also helps to derive useful information about the structure of the chosen compounds. A detailed interpretation of the Infrared and Raman spectra of the two molecules were reported based on potential energy distribution (PED). 13C and 1H NMR chemical shifts of the molecules were calculated using the gauge independent atomic orbital (GIAO) method. These studies satisfactorily agree the experimental data. Charge density distribution and site of chemical reactivity of the molecule have been studied by mapping electron density isosurface with molecular electrostatic potential (MEP). Stability of the molecules arising from hyperconjugative interactions, charge delocalization have been analyzed using natural bond orbital (NBO) analysis. The compounds have similar HOMO (Highest Occupied Molecular Orbitals) - LUMO (Lowest Unoccupied Molecular Orbitals) gap due to similarity in their structures. The compounds show (π→ π*) transitions in the UV- Visible range.
关键词： NMR,1-(2-methoxyphenyl)piperazine,Natural bond orbitals,DFT,1-(2-chlorophenyl)piperazine,HOMO-LUMO
更新于2025-09-10 09:29:36
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Surface enhanced Raman spectroscopy with methyl-orange on Ag-TiO2 nanocomposites: Experimental and theoretical investigation
摘要： Ag-TiO2 nanocomposites of different Ag nanoparticle (NP) concentrations are experimentally prepared and their UV-vis and surface enhanced Raman scattering characteristics are determined. The enhancement of the Raman signal for the ligand methyl-orange (MO) adsorbed onto the nanocomposite system, is observed. To investigate the influence of changing Ag concentration in this nanocomposite system, molecular dynamics (MD) simulations are conducted with both a fixed as well as varying number of the surfactant MO adsorbed onto the nanocomposite. Density functional theory (DFT) simulations are performed to investigate the conditions for charge transfer from the MO surfactant via the highest occupied molecular orbitals (HOMO), lowest unoccupied molecular orbitals (LUMO) as well as the electrostatic potentials. It is shown that the bonding mode of the surfactant contributes greatly to the observed Raman scattering enhancement.
关键词： HOMO-LUMO,Surface Enhanced Raman Scattering,density functional theory,molecular dynamics,Ag-TiO2 nanocomposite,electrostatic potential
更新于2025-09-09 09:28:46
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Periodic polymers with increasing repetition unit: Energy structure and carrier transfer
摘要： We study the energy structure and the transfer of an extra electron or hole along periodic polymers made of N monomers, with a repetition unit made of P monomers, using a tight-binding wire model, where a site is a monomer (e.g., in DNA, a base pair), for P even, and deal with two categories of such polymers: made of the same monomer (GC …, GGCC …, etc.) and made of different monomers (GA …, GGAA …, etc.). We calculate the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) eigenspectra, density of states, and HOMO-LUMO gap and find some limiting properties these categories possess, as P increases. We further examine the properties of the mean over time probability to find the carrier at each monomer. We introduce the weighted mean frequency of each monomer and the total weighted mean frequency of the whole polymer, as a measure of the overall transfer frequency content. We study the pure mean transfer rates. These rates can be increased by many orders of magnitude with appropriate sequence choice. Generally, homopolymers display the most efficient charge transfer. Finally, we compare the pure mean transfer rates with experimental transfer rates obtained by time-resolved spectroscopy.
关键词： LUMO,periodic polymers,weighted mean frequency,pure mean transfer rates,energy structure,carrier transfer,HOMO,density of states,HOMO-LUMO gap,tight-binding wire model
更新于2025-09-04 15:30:14
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Group 10 metal–thiocatecholate capped magnesium phthalocyanines – coupling chromophore and electron donor/acceptor entities and its impact on sulfur induced red-shifts
摘要： A new and facile method of generating thiolate groups at the phthalocyanine (Pc) β-position is presented as well the unique properties that these groups confer on the Pc ligand upon coordination of group 10 metals Ni, Pd and Pt(dppe) or SnMe3. In particular, the Q-band is shifted to almost 800 nm for all group 10 metals used, and the complexes show panchromatic absorption owing to new absorbance bands that appear between 400 and 650 nm. Enhanced intersystem-crossing for all transition metal co-ordinated Mg(Pc) complexes was demonstrated by the moderate to very high singlet oxygen quantum yields of 0.36, 0.76 and 0.91 for the Ni, Pd and Pt coordinating complexes, respectively, which show that the heavy metals have direct influence on the Pc π-system and inter-system-crossing (ISC). This was further confirmed by MO calculations, which show mixing of metal and ligand orbitals, as well as suggest that the Q-band transition has both π → π* and ligand-to-metal charge transfer characteristics. Furthermore, the origin of the Q-band red-shift was shown to be due to greater destabilization of the HOMO compared to LUMO/LUMO+1, thus decreasing the HOMO–LUMO band gap.
关键词： thiolate groups,intersystem-crossing,phthalocyanine,MO calculations,HOMO–LUMO band gap,panchromatic absorption,singlet oxygen quantum yields,group 10 metals,Q-band
更新于2025-09-04 15:30:14