The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Kun Gao - One of the best experts on this subject based on the ideXlab platform.
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directional and ultrafast migrations of excitons biexcitons in organic polymers by utilizing a local Nonuniform Electric Field
Journal of Materials Chemistry C, 2020Co-Authors: Maomao Zhang, Wei Qin, Kun GaoAbstract:In organic devices, migration dynamics of different excited states (e.g., excitons and biexcitons) are of vital importance to their functional processes. Here, by utilizing a local Nonuniform Electric Field to organic polymers, a new strategy to manipulate the directional and ultrafast migrations of both excitons and biexcitons has been theoretically reported. In particular, it is found that the direction of migration of biexcitons is opposite to that of excitons. The underlying mechanism is attributed to the reverse polarized behavior of excitons and biexcitons, on which reverse driving forces are separately created to act. Furthermore, to confirm and apply these theoretical findings, an experimental scheme is devised, aiming at luminescence modulation by manipulating the ultrafast redistribution of preformed excitons or biexcitons in an organic luminescent layer. The ranges of response time and visual resolution for the luminescence modulation have also been discussed.
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Directional and ultrafast migrations of excitons/biexcitons in organic polymers by utilizing a local Nonuniform Electric Field
Journal of Materials Chemistry C, 2020Co-Authors: Maomao Zhang, Wei Qin, Kun GaoAbstract:In organic devices, migration dynamics of different excited states (e.g., excitons and biexcitons) are of vital importance to their functional processes. Here, by utilizing a local Nonuniform Electric Field to organic polymers, a new strategy to manipulate the directional and ultrafast migrations of both excitons and biexcitons has been theoretically reported. In particular, it is found that the direction of migration of biexcitons is opposite to that of excitons. The underlying mechanism is attributed to the reverse polarized behavior of excitons and biexcitons, on which reverse driving forces are separately created to act. Furthermore, to confirm and apply these theoretical findings, an experimental scheme is devised, aiming at luminescence modulation by manipulating the ultrafast redistribution of preformed excitons or biexcitons in an organic luminescent layer. The ranges of response time and visual resolution for the luminescence modulation have also been discussed.
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charge separation from a cold charge transfer state driven by a Nonuniform Electric Field in polymer based donor acceptor heterojunctions
Journal of Physical Chemistry C, 2018Co-Authors: Maomao Zhang, Wei Qin, Kun GaoAbstract:Charge separation at donor/acceptor (D/A) interfaces plays a crucial role in the operation of photovoltaic polymer solar cells (PSCs), but the underlying mechanism still remains debated. Here, we present a model study to demonstrate how charge separation is achieved from a “cold” charge-transfer (CCT) state in the presence of a Nonuniform Electric Field along a continuous polymer-based D/A interface. We find that a CCT state experiences two kinds of evolution paths, which are determined by the Field strength of positions where the CCT state is initially generated. In strong-Field positions, the CCT state is directly dissociated into free charges, while in weak-Field positions, before the desired charge separation, the CCT state experiences an ultrafast migration process along the D/A interface. In both cases, charge separation takes place in a time scale less than 200 fs, which might contribute to the ultrafast charge separation reported experimentally in numerous high-performance PSCs. Finally, the mecha...
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Charge Separation from a “Cold” Charge-Transfer State Driven by a Nonuniform Electric Field in Polymer-Based Donor/Acceptor Heterojunctions
The Journal of Physical Chemistry C, 2018Co-Authors: Maomao Zhang, Wei Qin, Kun GaoAbstract:Charge separation at donor/acceptor (D/A) interfaces plays a crucial role in the operation of photovoltaic polymer solar cells (PSCs), but the underlying mechanism still remains debated. Here, we present a model study to demonstrate how charge separation is achieved from a “cold” charge-transfer (CCT) state in the presence of a Nonuniform Electric Field along a continuous polymer-based D/A interface. We find that a CCT state experiences two kinds of evolution paths, which are determined by the Field strength of positions where the CCT state is initially generated. In strong-Field positions, the CCT state is directly dissociated into free charges, while in weak-Field positions, before the desired charge separation, the CCT state experiences an ultrafast migration process along the D/A interface. In both cases, charge separation takes place in a time scale less than 200 fs, which might contribute to the ultrafast charge separation reported experimentally in numerous high-performance PSCs. Finally, the mecha...
Maomao Zhang - One of the best experts on this subject based on the ideXlab platform.
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directional and ultrafast migrations of excitons biexcitons in organic polymers by utilizing a local Nonuniform Electric Field
Journal of Materials Chemistry C, 2020Co-Authors: Maomao Zhang, Wei Qin, Kun GaoAbstract:In organic devices, migration dynamics of different excited states (e.g., excitons and biexcitons) are of vital importance to their functional processes. Here, by utilizing a local Nonuniform Electric Field to organic polymers, a new strategy to manipulate the directional and ultrafast migrations of both excitons and biexcitons has been theoretically reported. In particular, it is found that the direction of migration of biexcitons is opposite to that of excitons. The underlying mechanism is attributed to the reverse polarized behavior of excitons and biexcitons, on which reverse driving forces are separately created to act. Furthermore, to confirm and apply these theoretical findings, an experimental scheme is devised, aiming at luminescence modulation by manipulating the ultrafast redistribution of preformed excitons or biexcitons in an organic luminescent layer. The ranges of response time and visual resolution for the luminescence modulation have also been discussed.
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Directional and ultrafast migrations of excitons/biexcitons in organic polymers by utilizing a local Nonuniform Electric Field
Journal of Materials Chemistry C, 2020Co-Authors: Maomao Zhang, Wei Qin, Kun GaoAbstract:In organic devices, migration dynamics of different excited states (e.g., excitons and biexcitons) are of vital importance to their functional processes. Here, by utilizing a local Nonuniform Electric Field to organic polymers, a new strategy to manipulate the directional and ultrafast migrations of both excitons and biexcitons has been theoretically reported. In particular, it is found that the direction of migration of biexcitons is opposite to that of excitons. The underlying mechanism is attributed to the reverse polarized behavior of excitons and biexcitons, on which reverse driving forces are separately created to act. Furthermore, to confirm and apply these theoretical findings, an experimental scheme is devised, aiming at luminescence modulation by manipulating the ultrafast redistribution of preformed excitons or biexcitons in an organic luminescent layer. The ranges of response time and visual resolution for the luminescence modulation have also been discussed.
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charge separation from a cold charge transfer state driven by a Nonuniform Electric Field in polymer based donor acceptor heterojunctions
Journal of Physical Chemistry C, 2018Co-Authors: Maomao Zhang, Wei Qin, Kun GaoAbstract:Charge separation at donor/acceptor (D/A) interfaces plays a crucial role in the operation of photovoltaic polymer solar cells (PSCs), but the underlying mechanism still remains debated. Here, we present a model study to demonstrate how charge separation is achieved from a “cold” charge-transfer (CCT) state in the presence of a Nonuniform Electric Field along a continuous polymer-based D/A interface. We find that a CCT state experiences two kinds of evolution paths, which are determined by the Field strength of positions where the CCT state is initially generated. In strong-Field positions, the CCT state is directly dissociated into free charges, while in weak-Field positions, before the desired charge separation, the CCT state experiences an ultrafast migration process along the D/A interface. In both cases, charge separation takes place in a time scale less than 200 fs, which might contribute to the ultrafast charge separation reported experimentally in numerous high-performance PSCs. Finally, the mecha...
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Charge Separation from a “Cold” Charge-Transfer State Driven by a Nonuniform Electric Field in Polymer-Based Donor/Acceptor Heterojunctions
The Journal of Physical Chemistry C, 2018Co-Authors: Maomao Zhang, Wei Qin, Kun GaoAbstract:Charge separation at donor/acceptor (D/A) interfaces plays a crucial role in the operation of photovoltaic polymer solar cells (PSCs), but the underlying mechanism still remains debated. Here, we present a model study to demonstrate how charge separation is achieved from a “cold” charge-transfer (CCT) state in the presence of a Nonuniform Electric Field along a continuous polymer-based D/A interface. We find that a CCT state experiences two kinds of evolution paths, which are determined by the Field strength of positions where the CCT state is initially generated. In strong-Field positions, the CCT state is directly dissociated into free charges, while in weak-Field positions, before the desired charge separation, the CCT state experiences an ultrafast migration process along the D/A interface. In both cases, charge separation takes place in a time scale less than 200 fs, which might contribute to the ultrafast charge separation reported experimentally in numerous high-performance PSCs. Finally, the mecha...
Jungho Kim - One of the best experts on this subject based on the ideXlab platform.
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Heat transfer and bubble detachment in subcooled pool boiling from a downward-facing microheater array in a Nonuniform Electric Field.
Annals of the New York Academy of Sciences, 2009Co-Authors: Zan Liu, Cila Herman, Jungho KimAbstract:The effects of a Nonuniform Electric Field on vapor bubble detachment and heat transfer in subcooled pool boiling from a microheater array are investigated. The heater array faced downward to simulate a -1 g gravity condition and to eliminate the dominant masking effect of the buoyancy force. Experiments were conducted at different subcooling levels for various wall temperatures and Electric Field magnitudes. A diElectric fluid, FC-72, was used as the working fluid at ambient pressure. The array of 3 x 3 independently controlled microheaters was maintained at constant temperature and the rate of heat transfer from each heater was measured. Bubble images were recorded using a high-speed camera. The Electric Field was applied between the horizontal downward-facing microheater array, which was grounded, and a spherical, off-axis electrode beneath it. Boiling heat transfer results with and without the Electric Field are presented in this study. In the absence of the Nonuniform Electric Field, compared to the same bulk fluid temperature and wall superheat settings in the +1 g situation, a much larger primary bubble was formed on the heater array, due to the coalescence of the secondary bubbles that nucleated on the heater array. The vapor bubble remained on the heater array surface and no bubble detachment was observed. With the Nonuniform Electric Field applied, bubbles were lifted and sheared off from the heater array surface. The Electric Field was able to break up the primary bubble into several smaller bubbles--considerably greater heat transfer enhancement was measured than under similar conditions in +1 g.
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Heat Transfer and Bubble Detachment in Subcooled Pool Boiling From a Microheater Array Under the Effect of a Nonuniform Electric Field
ASME JSME 2007 Thermal Engineering Heat Transfer Summer Conference Volume 2, 2007Co-Authors: Zan Liu, Cila Herman, Jungho KimAbstract:The effects of a Nonuniform Electric Field on vapor bubble detachment and heat transfer rate were studied in pool boiling at different subcooled conditions for various wall temperatures. DiElectric fluid (FC-72) was used as the working fluid at 1 atm at earth gravity with two extreme gas concentration levels. An array of 3×3 independently controlled microheaters each 0.7×0.7 mm2 in size were maintained at constant temperature using electronic feedback loops, enabling the heat transfer from each heater to be determined. An Electric Field was applied between the horizontal upward facing microheater array, which was grounded, and a spherical, off-axis top electrode. Boiling heat transfer results with and without the Electric Field are presented in this study. Without the Electric Field, a single large “primary” bubble was observed to form due to the coalescence of the individual “satellite” bubbles which nucleated directly from each single heater array. Before its detachment, a dry spot formed underneath this primary bubble resulted in a reduction in heat transfer. With the Electric Field applied, three or more small “secondary” bubbles that nucleated and grew more rapidly and detached more frequently were observed. Due to the Nonuniformity of the Electric Field, bubbles moved away from the top electrode (into the weaker region of the Electric Field) during their development. Higher overall heat transfer rates were measured from the heater array. In addition, the bubble behavior showed agreement with our previous investigation of injecting air bubbles into a stagnant, isothermal liquid through orifices.Copyright © 2007 by ASME
Zan Liu - One of the best experts on this subject based on the ideXlab platform.
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Heat transfer and bubble detachment in subcooled pool boiling from a downward-facing microheater array in a Nonuniform Electric Field.
Annals of the New York Academy of Sciences, 2009Co-Authors: Zan Liu, Cila Herman, Jungho KimAbstract:The effects of a Nonuniform Electric Field on vapor bubble detachment and heat transfer in subcooled pool boiling from a microheater array are investigated. The heater array faced downward to simulate a -1 g gravity condition and to eliminate the dominant masking effect of the buoyancy force. Experiments were conducted at different subcooling levels for various wall temperatures and Electric Field magnitudes. A diElectric fluid, FC-72, was used as the working fluid at ambient pressure. The array of 3 x 3 independently controlled microheaters was maintained at constant temperature and the rate of heat transfer from each heater was measured. Bubble images were recorded using a high-speed camera. The Electric Field was applied between the horizontal downward-facing microheater array, which was grounded, and a spherical, off-axis electrode beneath it. Boiling heat transfer results with and without the Electric Field are presented in this study. In the absence of the Nonuniform Electric Field, compared to the same bulk fluid temperature and wall superheat settings in the +1 g situation, a much larger primary bubble was formed on the heater array, due to the coalescence of the secondary bubbles that nucleated on the heater array. The vapor bubble remained on the heater array surface and no bubble detachment was observed. With the Nonuniform Electric Field applied, bubbles were lifted and sheared off from the heater array surface. The Electric Field was able to break up the primary bubble into several smaller bubbles--considerably greater heat transfer enhancement was measured than under similar conditions in +1 g.
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Heat Transfer and Bubble Detachment in Subcooled Pool Boiling From a Microheater Array Under the Effect of a Nonuniform Electric Field
ASME JSME 2007 Thermal Engineering Heat Transfer Summer Conference Volume 2, 2007Co-Authors: Zan Liu, Cila Herman, Jungho KimAbstract:The effects of a Nonuniform Electric Field on vapor bubble detachment and heat transfer rate were studied in pool boiling at different subcooled conditions for various wall temperatures. DiElectric fluid (FC-72) was used as the working fluid at 1 atm at earth gravity with two extreme gas concentration levels. An array of 3×3 independently controlled microheaters each 0.7×0.7 mm2 in size were maintained at constant temperature using electronic feedback loops, enabling the heat transfer from each heater to be determined. An Electric Field was applied between the horizontal upward facing microheater array, which was grounded, and a spherical, off-axis top electrode. Boiling heat transfer results with and without the Electric Field are presented in this study. Without the Electric Field, a single large “primary” bubble was observed to form due to the coalescence of the individual “satellite” bubbles which nucleated directly from each single heater array. Before its detachment, a dry spot formed underneath this primary bubble resulted in a reduction in heat transfer. With the Electric Field applied, three or more small “secondary” bubbles that nucleated and grew more rapidly and detached more frequently were observed. Due to the Nonuniformity of the Electric Field, bubbles moved away from the top electrode (into the weaker region of the Electric Field) during their development. Higher overall heat transfer rates were measured from the heater array. In addition, the bubble behavior showed agreement with our previous investigation of injecting air bubbles into a stagnant, isothermal liquid through orifices.Copyright © 2007 by ASME
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Visualization of Vertical Bubble Coalescence and Detachment Under the Influence of a Nonuniform Electric Field
Heat Transfer Volume 2, 2006Co-Authors: Zan Liu, C. Herman, D. MewesAbstract:The effect of a Nonuniform Electric Field on the formation, coalescence and detachment of air bubbles injected into a stagnant, isothermal liquid through an orifice is studied to identify characteristic bubble behavior patterns. The results of the experimental visualization suggest significant differences in bubble shape and size caused by the Electric Field. The Electric Field was applied between a flat, circular and horizontal ground electrode and a spherical, off-axis top electrode. During formation the bubble was tilted towards or away from the upper electrode under the influence of the Electric Field. The direction of the tilt alternated (even in a single experiment), however, in the majority of the cases the bubble trajectory tilted towards the top electrode. The detachment frequency increased under the influence of the Electric Field, which indicates decreased bubble volume for lower volume flow rates. The effect of the Electric Field on vertical bubble coalescence was analyzed and quantified in terms of the detachment time.Copyright © 2006 by ASME
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Visualization of bubble detachment and coalescence under the influence of a Nonuniform Electric Field
Experimental Thermal and Fluid Science, 2006Co-Authors: Zan Liu, Cila Herman, D. MewesAbstract:The effect of a Nonuniform Electric Field on the formation, coalescence and detachment of single bubbles and pairs of air bubbles injected into a stagnant, isothermal liquid through orifices is studied to identify characteristic bubble behavior patterns. The results of the experimental visualization clearly indicate the significant differences in bubble shape, size and trajectory caused by the Electric Field. The Electric Field was applied between a flat, circular and horizontal ground electrode and a spherical, off-axis top electrode. In single bubble experiments the bubble was tilted towards or away from the upper electrode under the influence of the Electric Field. Although the direction of the tilt alternated (even in a single experiment), in the majority of the cases the bubble trajectory tilted towards the top electrode. In bubble pair experiments the bubbles behaved similarly to the single bubble case at larger volume flow rates. In low volume flow rate experiments the bubbles were tilted away from each other. Furthermore, the detachment frequency increased under the influence of the Electric Field, which indicates decreased bubble volume for lower volume flow rates. The effect of the Electric Field on vertical and lateral bubble coalescence was analyzed and quantified in terms of the detachment time.
Wei Qin - One of the best experts on this subject based on the ideXlab platform.
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directional and ultrafast migrations of excitons biexcitons in organic polymers by utilizing a local Nonuniform Electric Field
Journal of Materials Chemistry C, 2020Co-Authors: Maomao Zhang, Wei Qin, Kun GaoAbstract:In organic devices, migration dynamics of different excited states (e.g., excitons and biexcitons) are of vital importance to their functional processes. Here, by utilizing a local Nonuniform Electric Field to organic polymers, a new strategy to manipulate the directional and ultrafast migrations of both excitons and biexcitons has been theoretically reported. In particular, it is found that the direction of migration of biexcitons is opposite to that of excitons. The underlying mechanism is attributed to the reverse polarized behavior of excitons and biexcitons, on which reverse driving forces are separately created to act. Furthermore, to confirm and apply these theoretical findings, an experimental scheme is devised, aiming at luminescence modulation by manipulating the ultrafast redistribution of preformed excitons or biexcitons in an organic luminescent layer. The ranges of response time and visual resolution for the luminescence modulation have also been discussed.
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Directional and ultrafast migrations of excitons/biexcitons in organic polymers by utilizing a local Nonuniform Electric Field
Journal of Materials Chemistry C, 2020Co-Authors: Maomao Zhang, Wei Qin, Kun GaoAbstract:In organic devices, migration dynamics of different excited states (e.g., excitons and biexcitons) are of vital importance to their functional processes. Here, by utilizing a local Nonuniform Electric Field to organic polymers, a new strategy to manipulate the directional and ultrafast migrations of both excitons and biexcitons has been theoretically reported. In particular, it is found that the direction of migration of biexcitons is opposite to that of excitons. The underlying mechanism is attributed to the reverse polarized behavior of excitons and biexcitons, on which reverse driving forces are separately created to act. Furthermore, to confirm and apply these theoretical findings, an experimental scheme is devised, aiming at luminescence modulation by manipulating the ultrafast redistribution of preformed excitons or biexcitons in an organic luminescent layer. The ranges of response time and visual resolution for the luminescence modulation have also been discussed.
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charge separation from a cold charge transfer state driven by a Nonuniform Electric Field in polymer based donor acceptor heterojunctions
Journal of Physical Chemistry C, 2018Co-Authors: Maomao Zhang, Wei Qin, Kun GaoAbstract:Charge separation at donor/acceptor (D/A) interfaces plays a crucial role in the operation of photovoltaic polymer solar cells (PSCs), but the underlying mechanism still remains debated. Here, we present a model study to demonstrate how charge separation is achieved from a “cold” charge-transfer (CCT) state in the presence of a Nonuniform Electric Field along a continuous polymer-based D/A interface. We find that a CCT state experiences two kinds of evolution paths, which are determined by the Field strength of positions where the CCT state is initially generated. In strong-Field positions, the CCT state is directly dissociated into free charges, while in weak-Field positions, before the desired charge separation, the CCT state experiences an ultrafast migration process along the D/A interface. In both cases, charge separation takes place in a time scale less than 200 fs, which might contribute to the ultrafast charge separation reported experimentally in numerous high-performance PSCs. Finally, the mecha...
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Charge Separation from a “Cold” Charge-Transfer State Driven by a Nonuniform Electric Field in Polymer-Based Donor/Acceptor Heterojunctions
The Journal of Physical Chemistry C, 2018Co-Authors: Maomao Zhang, Wei Qin, Kun GaoAbstract:Charge separation at donor/acceptor (D/A) interfaces plays a crucial role in the operation of photovoltaic polymer solar cells (PSCs), but the underlying mechanism still remains debated. Here, we present a model study to demonstrate how charge separation is achieved from a “cold” charge-transfer (CCT) state in the presence of a Nonuniform Electric Field along a continuous polymer-based D/A interface. We find that a CCT state experiences two kinds of evolution paths, which are determined by the Field strength of positions where the CCT state is initially generated. In strong-Field positions, the CCT state is directly dissociated into free charges, while in weak-Field positions, before the desired charge separation, the CCT state experiences an ultrafast migration process along the D/A interface. In both cases, charge separation takes place in a time scale less than 200 fs, which might contribute to the ultrafast charge separation reported experimentally in numerous high-performance PSCs. Finally, the mecha...
