The Experts below are selected from a list of 2421 Experts worldwide ranked by ideXlab platform
Jenny Nelson - One of the best experts on this subject based on the ideXlab platform.
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Hybrid Polymer/Zinc Oxide Photovoltaic Devices with Vertically Oriented ZnO Nanorods and an Amphiphilic Molecular Interface Layer
The journal of physical chemistry. B, 2006Co-Authors: P Ravirajan, Ana M Peiro, Mohammed K Nazeeruddin, Michael Graetzel, D D C Bradley, James R Durrant, Jenny NelsonAbstract:We report on the effect of nanoparticle morphology and interfacial modification on the performance of hybrid polymer/zinc oxide photovoltaic devices. We compare structures consisting of poly-3-hexylthiophene (P3HT) polymer in contact with three different types of ZnO Layer: a flat ZnO Backing Layer alone; vertically aligned ZnO nanorods on a ZnO Backing Layer; and ZnO nanoparticles on a ZnO Backing Layer. We use scanning electron microscopy, steady state and transient absorption spectroscopies, and photovoltaic device measurements to study the morphology, charge separation, recombination behavior and device performance of the three types of structures. We find that charge recombination in the structures containing vertically aligned ZnO nanorods is remarkably slow, with a half-life of several milliseconds, over 2 orders of magnitude slower than that for randomly oriented ZnO nanoparticles. A photovoltaic device based on the nanorod structure that has been treated with an amphiphilic dye before deposition...
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hybrid polymer zinc oxide photovoltaic devices with vertically oriented zno nanorods and an amphiphilic molecular interface Layer
Journal of Physical Chemistry B, 2006Co-Authors: P Ravirajan, Ana M Peiro, Mohammed K Nazeeruddin, Michael Graetzel, D D C Bradley, James R Durrant, Jenny NelsonAbstract:We report on the effect of nanoparticle morphology and interfacial modification on the performance of hybrid polymer/zinc oxide photovoltaic devices. We compare structures consisting of poly-3-hexylthiophene (P3HT) polymer in contact with three different types of ZnO Layer: a flat ZnO Backing Layer alone; vertically aligned ZnO nanorods on a ZnO Backing Layer; and ZnO nanoparticles on a ZnO Backing Layer. We use scanning electron microscopy, steady state and transient absorption spectroscopies, and photovoltaic device measurements to study the morphology, charge separation, recombination behavior and device performance of the three types of structures. We find that charge recombination in the structures containing vertically aligned ZnO nanorods is remarkably slow, with a half-life of several milliseconds, over 2 orders of magnitude slower than that for randomly oriented ZnO nanoparticles. A photovoltaic device based on the nanorod structure that has been treated with an amphiphilic dye before deposition...
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The effect of zinc oxide nanostructure on the performance of hybrid polymer/zinc oxide solar cells
Organic Photovoltaics VI, 2005Co-Authors: Ana M Peiro, P Ravirajan, D D C Bradley, Jenny Nelson, Kuveshni Govender, D. S. Boyle, Paul O'brien, James R DurrantAbstract:Solar cells fabricated from composites of conjugated polymers with nanostructured metal oxides are gaining interest on account of the stability, low cost and electron transport properties of metal oxides. Zinc oxide (ZnO)/polymer solar cells are promising compared to other metal oxide/polymer combinations, on account of the possibility of low temperature synthesis, as well as the potential for controlling interface morphology through simple processing from solution. Here, we focus on the effect of surface morphology of ZnO films on photovoltaic device performance. We have successfully grown ZnO nanorods standing almost perpendicular to the electrodes on a flat, dense ZnO "Backing" Layer. We studied structures consisting of a conjugated polymer in contact with three different types of ZnO Layer: a flat ZnO Backing Layer alone; ZnO nanorods on a ZnO Backing Layer; and ZnO nanoparticles on a ZnO Backing Layer. We use scanning electron microscopy, steady state and transient absorption spectroscopies and photovoltaic device measurements to study the morphology, charge separation and recombination behaviour and device performance of the three types of structures. We find that charge recombination in the structures containing vertically aligned ZnO nanorods is remarkably slow, with a half life of over 1 ms, over two orders of magnitude slower than for randomly oriented ZnO nanoparticles. A photovoltaic device based on the nanorod structure which has been treated with an ambiphilic dye before deposition of poly(3-hexyl thiophene) (P3HT) polymer shows a power conversion efficiency over four times greater than for a similar device based on the nanoparticle structure. The best ZnO nanorods: P3HT device yields a short circuit current density of 2 mAcm-2 under AM1.5 illumination (100mWcm-2) and peak external quantum efficiency over 14%, resulting in a power conversion efficiency of 0.20%.
Jong Seob Jeong - One of the best experts on this subject based on the ideXlab platform.
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A Phase-Canceled Backing Layer for Ultrasound Linear Array Transducer: Modeling and Experimental Verification
IEEE transactions on ultrasonics ferroelectrics and frequency control, 2019Co-Authors: Da Sol Kwon, Jin Ho Sung, Chan Yuk Park, Eun Young Jeong, Jong Seob JeongAbstract:In this study, a phase-canceled Backing Layer for ultrasound linear array transducer is presented. The proposed Backing Layer is composed of multiple blocks operated by a phase inversion technique. Inside the proposed Backing Layer, the phase of the reflected signals can be canceled by adjusting acoustic impedance, piezoelectric Layer contact area, and thickness of each block constituting the Backing Layer. Therefore, the total thickness of the Backing Layer can be significantly reduced while maintaining the performance. Using finite element analysis (FEA) simulation, its performance was verified based on an 8-MHz linear array transducer. Two types of bulk-type Backing Layers with different thicknesses were also simulated to compare the performance of the proposed method. In the case of a narrow bandwidth signal without the matching Layers, the 10-mm-thick bulk-type Backing Layer yielded a −6-dB bandwidth of 37.2%. When its thickness was reduced to 2 mm, the −6-dB bandwidth was decreased to 17.3% due to the reflected back-wall signals. However, the −6-dB bandwidth of the proposed Backing Layer with 2-mm thickness was 39.5%, which is similar to the thick bulk-type Backing Layer. In the case of broad bandwidth signal with the matching Layers, the proposed transducer also exhibits similar performance compared with the thick bulk-type Backing Layer. The narrow bandwidth signal was experimentally implemented by using a prototype array transducer with the proposed technique, and the performance was similar to the simulation. Thus, the proposed method can reduce the thickness of the Backing Layer of various array transducers.
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Phase-canceled Backing structure for lightweight ultrasonic transducer
Sensors and Actuators A: Physical, 2017Co-Authors: Jin Ho Sung, Chan Yuk Park, Jong Seob JeongAbstract:Abstract The overall weight of a medical ultrasonic transducer mainly depends on the weight of the Backing Layer. Therefore, a reduction of the thickness and the weight of the Backing Layer can be very useful for various types of array transducers whereby the user suffers from the inconvenience of the heavy weight. However, the Backing Layer with reduced thickness can cause distortions of the transmitted and received signals due to severe ripples reflected from the back-wall of the Backing Layer. In this study, a novel Backing structure is proposed to solve this problem. The suggested Backing Layer is composed of multiple Backing materials with different acoustic impedances to cancel the phases of the reflected signals. The rearmost material can dissipate the residual energy through the absorption effect. To verify these effects, a finite-element-method (FEM) simulation was conducted, and 4.5 MHz single-element transducers were fabricated. Although the thickness of the suggested Backing Layer was reduced by 1/5 compared with the conventional thick bulk-type Backing Layer, the ripples caused from the Backing Layer were successfully minimized. Therefore, the proposed Backing structure can be a potential way to reduce the thickness of the Backing Layer resulting in a lightweight ultrasonic transducer.
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improved fabrication of focused single element p vdf trfe transducer for high frequency ultrasound applications
Ultrasonics, 2013Co-Authors: Jong Seob Jeong, Kirk K ShungAbstract:We present an improved fabrication technique for the focused single element poly (vinylidene fluoride–trifluoroethylene) P(VDF–TrFE) transducer. In this work, a conductive epoxy for a Backing Layer was directly bonded to the 25 μm thick P(VDF–TrFE) film and thus made it easy to conform the aperture of the P(VDF–TrFE) transducer. Two prototype focused P(VDF–TrFE) transducers with disk- and ring-type aperture were fabricated and their performance was evaluated using the UBM (Ultrasound Biomicroscopy) system with a wire phantom. All transducers had a spherically focused aperture with a low f-number (focal depth/aperture size = 1). The center frequency of the disk-type P(VDF–TrFE) transducer was 23 MHz and −6 dB bandwidth was 102%. The ring-type P(VDF–TrFE) transducer had 20 MHz center frequency and −6 dB bandwidth of 103%. The measured pulse echo signal had reduced reverberation due to no additional adhesive Layer between the P(VDF–TrFE) film and the Backing Layer. Hence, the proposed method is promising to fabricate a single element transducer using P(VDF–TrFE) film for high frequency applications.
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Improved fabrication of focused single element P(VDF–TrFE) transducer for high frequency ultrasound applications
Ultrasonics, 2012Co-Authors: Jong Seob Jeong, Kirk K ShungAbstract:We present an improved fabrication technique for the focused single element poly (vinylidene fluoride–trifluoroethylene) P(VDF–TrFE) transducer. In this work, a conductive epoxy for a Backing Layer was directly bonded to the 25 μm thick P(VDF–TrFE) film and thus made it easy to conform the aperture of the P(VDF–TrFE) transducer. Two prototype focused P(VDF–TrFE) transducers with disk- and ring-type aperture were fabricated and their performance was evaluated using the UBM (Ultrasound Biomicroscopy) system with a wire phantom. All transducers had a spherically focused aperture with a low f-number (focal depth/aperture size = 1). The center frequency of the disk-type P(VDF–TrFE) transducer was 23 MHz and −6 dB bandwidth was 102%. The ring-type P(VDF–TrFE) transducer had 20 MHz center frequency and −6 dB bandwidth of 103%. The measured pulse echo signal had reduced reverberation due to no additional adhesive Layer between the P(VDF–TrFE) film and the Backing Layer. Hence, the proposed method is promising to fabricate a single element transducer using P(VDF–TrFE) film for high frequency applications.
Kirk K Shung - One of the best experts on this subject based on the ideXlab platform.
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improved fabrication of focused single element p vdf trfe transducer for high frequency ultrasound applications
Ultrasonics, 2013Co-Authors: Jong Seob Jeong, Kirk K ShungAbstract:We present an improved fabrication technique for the focused single element poly (vinylidene fluoride–trifluoroethylene) P(VDF–TrFE) transducer. In this work, a conductive epoxy for a Backing Layer was directly bonded to the 25 μm thick P(VDF–TrFE) film and thus made it easy to conform the aperture of the P(VDF–TrFE) transducer. Two prototype focused P(VDF–TrFE) transducers with disk- and ring-type aperture were fabricated and their performance was evaluated using the UBM (Ultrasound Biomicroscopy) system with a wire phantom. All transducers had a spherically focused aperture with a low f-number (focal depth/aperture size = 1). The center frequency of the disk-type P(VDF–TrFE) transducer was 23 MHz and −6 dB bandwidth was 102%. The ring-type P(VDF–TrFE) transducer had 20 MHz center frequency and −6 dB bandwidth of 103%. The measured pulse echo signal had reduced reverberation due to no additional adhesive Layer between the P(VDF–TrFE) film and the Backing Layer. Hence, the proposed method is promising to fabricate a single element transducer using P(VDF–TrFE) film for high frequency applications.
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Improved fabrication of focused single element P(VDF–TrFE) transducer for high frequency ultrasound applications
Ultrasonics, 2012Co-Authors: Jong Seob Jeong, Kirk K ShungAbstract:We present an improved fabrication technique for the focused single element poly (vinylidene fluoride–trifluoroethylene) P(VDF–TrFE) transducer. In this work, a conductive epoxy for a Backing Layer was directly bonded to the 25 μm thick P(VDF–TrFE) film and thus made it easy to conform the aperture of the P(VDF–TrFE) transducer. Two prototype focused P(VDF–TrFE) transducers with disk- and ring-type aperture were fabricated and their performance was evaluated using the UBM (Ultrasound Biomicroscopy) system with a wire phantom. All transducers had a spherically focused aperture with a low f-number (focal depth/aperture size = 1). The center frequency of the disk-type P(VDF–TrFE) transducer was 23 MHz and −6 dB bandwidth was 102%. The ring-type P(VDF–TrFE) transducer had 20 MHz center frequency and −6 dB bandwidth of 103%. The measured pulse echo signal had reduced reverberation due to no additional adhesive Layer between the P(VDF–TrFE) film and the Backing Layer. Hence, the proposed method is promising to fabricate a single element transducer using P(VDF–TrFE) film for high frequency applications.
P Ravirajan - One of the best experts on this subject based on the ideXlab platform.
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Hybrid Polymer/Zinc Oxide Photovoltaic Devices with Vertically Oriented ZnO Nanorods and an Amphiphilic Molecular Interface Layer
The journal of physical chemistry. B, 2006Co-Authors: P Ravirajan, Ana M Peiro, Mohammed K Nazeeruddin, Michael Graetzel, D D C Bradley, James R Durrant, Jenny NelsonAbstract:We report on the effect of nanoparticle morphology and interfacial modification on the performance of hybrid polymer/zinc oxide photovoltaic devices. We compare structures consisting of poly-3-hexylthiophene (P3HT) polymer in contact with three different types of ZnO Layer: a flat ZnO Backing Layer alone; vertically aligned ZnO nanorods on a ZnO Backing Layer; and ZnO nanoparticles on a ZnO Backing Layer. We use scanning electron microscopy, steady state and transient absorption spectroscopies, and photovoltaic device measurements to study the morphology, charge separation, recombination behavior and device performance of the three types of structures. We find that charge recombination in the structures containing vertically aligned ZnO nanorods is remarkably slow, with a half-life of several milliseconds, over 2 orders of magnitude slower than that for randomly oriented ZnO nanoparticles. A photovoltaic device based on the nanorod structure that has been treated with an amphiphilic dye before deposition...
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hybrid polymer zinc oxide photovoltaic devices with vertically oriented zno nanorods and an amphiphilic molecular interface Layer
Journal of Physical Chemistry B, 2006Co-Authors: P Ravirajan, Ana M Peiro, Mohammed K Nazeeruddin, Michael Graetzel, D D C Bradley, James R Durrant, Jenny NelsonAbstract:We report on the effect of nanoparticle morphology and interfacial modification on the performance of hybrid polymer/zinc oxide photovoltaic devices. We compare structures consisting of poly-3-hexylthiophene (P3HT) polymer in contact with three different types of ZnO Layer: a flat ZnO Backing Layer alone; vertically aligned ZnO nanorods on a ZnO Backing Layer; and ZnO nanoparticles on a ZnO Backing Layer. We use scanning electron microscopy, steady state and transient absorption spectroscopies, and photovoltaic device measurements to study the morphology, charge separation, recombination behavior and device performance of the three types of structures. We find that charge recombination in the structures containing vertically aligned ZnO nanorods is remarkably slow, with a half-life of several milliseconds, over 2 orders of magnitude slower than that for randomly oriented ZnO nanoparticles. A photovoltaic device based on the nanorod structure that has been treated with an amphiphilic dye before deposition...
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The effect of zinc oxide nanostructure on the performance of hybrid polymer/zinc oxide solar cells
Organic Photovoltaics VI, 2005Co-Authors: Ana M Peiro, P Ravirajan, D D C Bradley, Jenny Nelson, Kuveshni Govender, D. S. Boyle, Paul O'brien, James R DurrantAbstract:Solar cells fabricated from composites of conjugated polymers with nanostructured metal oxides are gaining interest on account of the stability, low cost and electron transport properties of metal oxides. Zinc oxide (ZnO)/polymer solar cells are promising compared to other metal oxide/polymer combinations, on account of the possibility of low temperature synthesis, as well as the potential for controlling interface morphology through simple processing from solution. Here, we focus on the effect of surface morphology of ZnO films on photovoltaic device performance. We have successfully grown ZnO nanorods standing almost perpendicular to the electrodes on a flat, dense ZnO "Backing" Layer. We studied structures consisting of a conjugated polymer in contact with three different types of ZnO Layer: a flat ZnO Backing Layer alone; ZnO nanorods on a ZnO Backing Layer; and ZnO nanoparticles on a ZnO Backing Layer. We use scanning electron microscopy, steady state and transient absorption spectroscopies and photovoltaic device measurements to study the morphology, charge separation and recombination behaviour and device performance of the three types of structures. We find that charge recombination in the structures containing vertically aligned ZnO nanorods is remarkably slow, with a half life of over 1 ms, over two orders of magnitude slower than for randomly oriented ZnO nanoparticles. A photovoltaic device based on the nanorod structure which has been treated with an ambiphilic dye before deposition of poly(3-hexyl thiophene) (P3HT) polymer shows a power conversion efficiency over four times greater than for a similar device based on the nanoparticle structure. The best ZnO nanorods: P3HT device yields a short circuit current density of 2 mAcm-2 under AM1.5 illumination (100mWcm-2) and peak external quantum efficiency over 14%, resulting in a power conversion efficiency of 0.20%.
James R Durrant - One of the best experts on this subject based on the ideXlab platform.
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Hybrid Polymer/Zinc Oxide Photovoltaic Devices with Vertically Oriented ZnO Nanorods and an Amphiphilic Molecular Interface Layer
The journal of physical chemistry. B, 2006Co-Authors: P Ravirajan, Ana M Peiro, Mohammed K Nazeeruddin, Michael Graetzel, D D C Bradley, James R Durrant, Jenny NelsonAbstract:We report on the effect of nanoparticle morphology and interfacial modification on the performance of hybrid polymer/zinc oxide photovoltaic devices. We compare structures consisting of poly-3-hexylthiophene (P3HT) polymer in contact with three different types of ZnO Layer: a flat ZnO Backing Layer alone; vertically aligned ZnO nanorods on a ZnO Backing Layer; and ZnO nanoparticles on a ZnO Backing Layer. We use scanning electron microscopy, steady state and transient absorption spectroscopies, and photovoltaic device measurements to study the morphology, charge separation, recombination behavior and device performance of the three types of structures. We find that charge recombination in the structures containing vertically aligned ZnO nanorods is remarkably slow, with a half-life of several milliseconds, over 2 orders of magnitude slower than that for randomly oriented ZnO nanoparticles. A photovoltaic device based on the nanorod structure that has been treated with an amphiphilic dye before deposition...
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hybrid polymer zinc oxide photovoltaic devices with vertically oriented zno nanorods and an amphiphilic molecular interface Layer
Journal of Physical Chemistry B, 2006Co-Authors: P Ravirajan, Ana M Peiro, Mohammed K Nazeeruddin, Michael Graetzel, D D C Bradley, James R Durrant, Jenny NelsonAbstract:We report on the effect of nanoparticle morphology and interfacial modification on the performance of hybrid polymer/zinc oxide photovoltaic devices. We compare structures consisting of poly-3-hexylthiophene (P3HT) polymer in contact with three different types of ZnO Layer: a flat ZnO Backing Layer alone; vertically aligned ZnO nanorods on a ZnO Backing Layer; and ZnO nanoparticles on a ZnO Backing Layer. We use scanning electron microscopy, steady state and transient absorption spectroscopies, and photovoltaic device measurements to study the morphology, charge separation, recombination behavior and device performance of the three types of structures. We find that charge recombination in the structures containing vertically aligned ZnO nanorods is remarkably slow, with a half-life of several milliseconds, over 2 orders of magnitude slower than that for randomly oriented ZnO nanoparticles. A photovoltaic device based on the nanorod structure that has been treated with an amphiphilic dye before deposition...
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The effect of zinc oxide nanostructure on the performance of hybrid polymer/zinc oxide solar cells
Organic Photovoltaics VI, 2005Co-Authors: Ana M Peiro, P Ravirajan, D D C Bradley, Jenny Nelson, Kuveshni Govender, D. S. Boyle, Paul O'brien, James R DurrantAbstract:Solar cells fabricated from composites of conjugated polymers with nanostructured metal oxides are gaining interest on account of the stability, low cost and electron transport properties of metal oxides. Zinc oxide (ZnO)/polymer solar cells are promising compared to other metal oxide/polymer combinations, on account of the possibility of low temperature synthesis, as well as the potential for controlling interface morphology through simple processing from solution. Here, we focus on the effect of surface morphology of ZnO films on photovoltaic device performance. We have successfully grown ZnO nanorods standing almost perpendicular to the electrodes on a flat, dense ZnO "Backing" Layer. We studied structures consisting of a conjugated polymer in contact with three different types of ZnO Layer: a flat ZnO Backing Layer alone; ZnO nanorods on a ZnO Backing Layer; and ZnO nanoparticles on a ZnO Backing Layer. We use scanning electron microscopy, steady state and transient absorption spectroscopies and photovoltaic device measurements to study the morphology, charge separation and recombination behaviour and device performance of the three types of structures. We find that charge recombination in the structures containing vertically aligned ZnO nanorods is remarkably slow, with a half life of over 1 ms, over two orders of magnitude slower than for randomly oriented ZnO nanoparticles. A photovoltaic device based on the nanorod structure which has been treated with an ambiphilic dye before deposition of poly(3-hexyl thiophene) (P3HT) polymer shows a power conversion efficiency over four times greater than for a similar device based on the nanoparticle structure. The best ZnO nanorods: P3HT device yields a short circuit current density of 2 mAcm-2 under AM1.5 illumination (100mWcm-2) and peak external quantum efficiency over 14%, resulting in a power conversion efficiency of 0.20%.
