The Experts below are selected from a list of 87 Experts worldwide ranked by ideXlab platform
Karthikeyan Chandrasekaran - One of the best experts on this subject based on the ideXlab platform.
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Spectroscopic (FT-IR, FT-Raman and NMR) and NBO analysis of 3, 4-dimethylanisole by density functional method
Indian Journal of Pure & Applied Physics, 2019Co-Authors: Sambath Kumar, S. Manimaran, N. Rajkamal, M. Venkatachalapathy, Karthikeyan ChandrasekaranAbstract:Combined experimental and theoretical studies have been conducted on the Molecular structure and vibrational, spectra of 3, 4-dimethyl anisole (DMA). The FT-IR and FT-Raman spectra of DMA have been recorded in the solid phase. The Molecular geometry and vibrational frequencies of DMA in the ground state have been calculated by using the ab-initio Hartree-Fock (HF) and density functional methods (B3LYP) invoking 6-31+G (d,p) basis set. The optimized geometric bond lengths and bond angles obtained by HF method shows best agreement with the experimental values. Comparison of the observed fundamental vibrational frequencies of DMA with calculated results by HF and density functional methods indicates that B3LYP is superior to the scaled HF approach for Molecular vibrational problems. The difference between the observed and scaled wave number values of most of the fundamental is very small. The thermodynamic functions and atomic change of the title compound has also been performed at HF/B3LYP/6-31+G(d,p) level of theories. A detailed interpretation of the FT-IR, FT-Raman, NMR spectra of DMA has also been reported. The theoretical spectrograms for infrared and Raman spectra of the title molecule have been constructed. The thermodynamic function of the title compound has also been performed at HF/6-31+G (d,p) and B3LYP/6-31+G (d,p) level of theories. Natural bond Orbital analysis has been carried out to explain the change transfer or delocalization of change due to the intra-Molecular interactions. Energy of the highest occupied Molecular (HOMO) Orbital and lowest unoccupied (LUMO) Molecular Orbital have been predicted.
Russell J Holmes - One of the best experts on this subject based on the ideXlab platform.
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Exciton diffusion in organic photovoltaic cells
Energy and Environmental Science, 2014Co-Authors: S M Menke, Russell J HolmesAbstract:Exciton generation, migration, and dissociation are key processes that play a central role in the design and operation of many organic optoelectronic devices. In organic photovoltaic cells, charge generation often occurs only at an interface, forcing the exciton to migrate from the point of photogeneration in order to be dissociated into its constituent charge carriers. Consequently, the design and performance of these devices is strongly impacted by the typically short distance over which excitons are able to move. The ability to engineer materials or device architectures with favorable exciton transport depends strongly on improving our understanding of the governing energy transfer mechanisms and rates. To this end, this review highlights recent efforts to better characterize, understand and ultimately engineer exciton transport. Broader context Excited state energy transfer processes play a central role in virtually all organic optoelectronic devices. An understanding of these processes is particularly critical in organic photovoltaic cells, a promising technology that aims to convert the energy from sunlight into electricity. Consisting of organic semiconductor thin lms, these devices are attractive for their compatibility with high throughput processing techniques and exible, lightweight substrates. This review focuses on exciton diffusion in organic semiconductors, a critical nanoscale process that is driven by the relative efficiency of interMolecular energy transfer in these materials. Highlighted is current and future research aiming to engineer efficient exciton diffusion for next generation organic photovoltaic devices. With the demonstration of the rst organic heterojunction photovoltaic device more than 25 years ago, the fundamental understanding of organic photovoltaic cells (OPVs) has pro-gressed rapidly. 1–6 Power conversion efficiencies for state of the art OPVs now exceed 10%, 7 driving intense activity in full-scale commercialization. Photovoltaic cells based on organic semi-conductors are also attractive for their compatibility with low-cost, large area processing techniques. 8 Photoconversion in an OPV can be broken down into four key processes, each with its own efficiency (Fig. 1) namely, photon absorption and exciton generation (h A), exciton diffusion (h D), exciton dissoci-ation by charge transfer (h CT), and charge carrier collection (h CC). 9 The product of these four efficiencies is the external quantum efficiency (h EQE). Integration of the h EQE across the solar spectrum yields the short-circuit current density (J SC), one of three critical device parameters, along with the open-circuit voltage (V OC) and ll factor, which combine to dene the power conversion efficiency (h P). In the simplest conguration, an OPV contains a planar or bilayer heterojunction between thin lms of electron donating and accepting materials. The active materials are chosen to realize an offset in the highest occupied (HOMO) and lowest unoccupied (LUMO) Molecular Orbital energy levels at the donor–acceptor (D–A) interface to drive exciton dissociation by charge transfer (Fig. 1). In order to realize efficient photoconversion, this architecture must strike a balance between the relatively long optical absorption length (L A $ 50 nm) and the shorter characteristic length scale for exciton diffusion (L D $ 10 nm). 2 Referred to as the exciton bottleneck, this trade-off limits the absorption–diffusion efficiency product thereby limiting h EQE and J SC .
Yusuf Erdogdu - One of the best experts on this subject based on the ideXlab platform.
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FT-IR, FT-Raman, NMR spectral analysis and theoretical NBO, HOMO―LUMO analysis of bis(4-amino-5-mercapto-1,2,4-triazol-3-yl)ethane by ab initio HF and DFT methods
Journal of Molecular Structure, 2010Co-Authors: S. Subashchandrabose, Akhil R. Krishnan, H. Saleem, Venugopal Thanikachalam, G. Manikandan, Yusuf ErdogduAbstract:Abstract A combined experimental and theoretical studies were conducted on the Molecular structure and vibrational spectra of bis(4-amino-5-mercapto-1,2,4-triazol-3-yl) ethane (BAMTE). The FT-IR and FT-Raman spectra of BAMTE were recorded in the solid phase. The Molecular geometry and vibrational frequencies of BAMTE in the ground state have been calculated by using the ab initio HF (Hartree–Fock) and density functional methods (B3LYP) invoking 6-311++G(d,p) basis set. The optimized geometric bond lengths and bond angles obtained by HF method shows best agreement with the experimental values. Comparison of the observed fundamental vibrational frequencies of BAMTE with calculated results by HF and density functional methods indicates that B3LYP is superior to the scaled Hartree–Fock approach for Molecular vibrational problems. The difference between the observed and scaled wave number values of most of the fundamentals is very small. The thermodynamic functions and atomic charges of the title compound was also performed at HF/B3LYP/6-311++G(d,p) level of theories. A detailed interpretation of the FT-IR, FT-Raman, NMR spectra of BAMTE was also reported. The theoretical spectrograms for Infrared and Raman spectra of the title molecule have been constructed. Natural bond Orbital analysis has been carried out to explain the charge transfer or delocalization of charge due to the intra-Molecular interactions. Energy of the highest occupied Molecular (HOMO) Orbital and lowest unoccupied (LUMO) Molecular Orbital have been predicted.
Sambath Kumar - One of the best experts on this subject based on the ideXlab platform.
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Spectroscopic (FT-IR, FT-Raman and NMR) and NBO analysis of 3, 4-dimethylanisole by density functional method
Indian Journal of Pure & Applied Physics, 2019Co-Authors: Sambath Kumar, S. Manimaran, N. Rajkamal, M. Venkatachalapathy, Karthikeyan ChandrasekaranAbstract:Combined experimental and theoretical studies have been conducted on the Molecular structure and vibrational, spectra of 3, 4-dimethyl anisole (DMA). The FT-IR and FT-Raman spectra of DMA have been recorded in the solid phase. The Molecular geometry and vibrational frequencies of DMA in the ground state have been calculated by using the ab-initio Hartree-Fock (HF) and density functional methods (B3LYP) invoking 6-31+G (d,p) basis set. The optimized geometric bond lengths and bond angles obtained by HF method shows best agreement with the experimental values. Comparison of the observed fundamental vibrational frequencies of DMA with calculated results by HF and density functional methods indicates that B3LYP is superior to the scaled HF approach for Molecular vibrational problems. The difference between the observed and scaled wave number values of most of the fundamental is very small. The thermodynamic functions and atomic change of the title compound has also been performed at HF/B3LYP/6-31+G(d,p) level of theories. A detailed interpretation of the FT-IR, FT-Raman, NMR spectra of DMA has also been reported. The theoretical spectrograms for infrared and Raman spectra of the title molecule have been constructed. The thermodynamic function of the title compound has also been performed at HF/6-31+G (d,p) and B3LYP/6-31+G (d,p) level of theories. Natural bond Orbital analysis has been carried out to explain the change transfer or delocalization of change due to the intra-Molecular interactions. Energy of the highest occupied Molecular (HOMO) Orbital and lowest unoccupied (LUMO) Molecular Orbital have been predicted.
S M Menke - One of the best experts on this subject based on the ideXlab platform.
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Exciton diffusion in organic photovoltaic cells
Energy and Environmental Science, 2014Co-Authors: S M Menke, Russell J HolmesAbstract:Exciton generation, migration, and dissociation are key processes that play a central role in the design and operation of many organic optoelectronic devices. In organic photovoltaic cells, charge generation often occurs only at an interface, forcing the exciton to migrate from the point of photogeneration in order to be dissociated into its constituent charge carriers. Consequently, the design and performance of these devices is strongly impacted by the typically short distance over which excitons are able to move. The ability to engineer materials or device architectures with favorable exciton transport depends strongly on improving our understanding of the governing energy transfer mechanisms and rates. To this end, this review highlights recent efforts to better characterize, understand and ultimately engineer exciton transport. Broader context Excited state energy transfer processes play a central role in virtually all organic optoelectronic devices. An understanding of these processes is particularly critical in organic photovoltaic cells, a promising technology that aims to convert the energy from sunlight into electricity. Consisting of organic semiconductor thin lms, these devices are attractive for their compatibility with high throughput processing techniques and exible, lightweight substrates. This review focuses on exciton diffusion in organic semiconductors, a critical nanoscale process that is driven by the relative efficiency of interMolecular energy transfer in these materials. Highlighted is current and future research aiming to engineer efficient exciton diffusion for next generation organic photovoltaic devices. With the demonstration of the rst organic heterojunction photovoltaic device more than 25 years ago, the fundamental understanding of organic photovoltaic cells (OPVs) has pro-gressed rapidly. 1–6 Power conversion efficiencies for state of the art OPVs now exceed 10%, 7 driving intense activity in full-scale commercialization. Photovoltaic cells based on organic semi-conductors are also attractive for their compatibility with low-cost, large area processing techniques. 8 Photoconversion in an OPV can be broken down into four key processes, each with its own efficiency (Fig. 1) namely, photon absorption and exciton generation (h A), exciton diffusion (h D), exciton dissoci-ation by charge transfer (h CT), and charge carrier collection (h CC). 9 The product of these four efficiencies is the external quantum efficiency (h EQE). Integration of the h EQE across the solar spectrum yields the short-circuit current density (J SC), one of three critical device parameters, along with the open-circuit voltage (V OC) and ll factor, which combine to dene the power conversion efficiency (h P). In the simplest conguration, an OPV contains a planar or bilayer heterojunction between thin lms of electron donating and accepting materials. The active materials are chosen to realize an offset in the highest occupied (HOMO) and lowest unoccupied (LUMO) Molecular Orbital energy levels at the donor–acceptor (D–A) interface to drive exciton dissociation by charge transfer (Fig. 1). In order to realize efficient photoconversion, this architecture must strike a balance between the relatively long optical absorption length (L A $ 50 nm) and the shorter characteristic length scale for exciton diffusion (L D $ 10 nm). 2 Referred to as the exciton bottleneck, this trade-off limits the absorption–diffusion efficiency product thereby limiting h EQE and J SC .
