The Experts below are selected from a list of 261 Experts worldwide ranked by ideXlab platform
Kijung Yong - One of the best experts on this subject based on the ideXlab platform.
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hybrid type quantum dot cosensitized zno Nanowire Solar Cell with enhanced visible light harvesting
ACS Applied Materials & Interfaces, 2013Co-Authors: Heejin Kim, Hyuncheol Jeong, Chan Eon Park, Kijung YongAbstract:A polymer hybrid quantum-dot-sensitized Solar Cell was developed using CdSe/CdS/ZnO Nanowires as a photoanode and regioregular P3HT as a conjugated polymer. The P3HT polymer was used as a hole tran...
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Hybrid-type quantum-dot cosensitized ZnO Nanowire Solar Cell with enhanced visible-light harvesting
ACS Applied Materials and Interfaces, 2013Co-Authors: Heejin Kim, Hyuncheol Jeong, Tae Kyu An, Chan Eon Park, Kijung YongAbstract:A polymer hybrid quantum-dot-sensitized Solar Cell was developed using CdSe/CdS/ZnO Nanowires as a photoanode and regioregular P3HT as a conjugated polymer. The P3HT polymer was used as a hole transport material to replace the liquid electrolyte in quantum dot sensitized Solar Cells, CdSe/CdS acts as a cosensitizer, which enhances light harvesting in the visible range, and the ZnO Nanowires provide a direct pathway for electron transport. Through an adequate cascade bandgap structure of the photoanode, the photoexcited electrons were effectively separated from the electron/hole pairs and transported under illumination. The remaining holes at the anode were transported by the conjugated polymer P3HT without any intermediate potential loss. The fabrication of the hybrid Solar Cell was optimized with various experimental conditions, including the length of the ZnO Nanowires, quantum sensitizers, P3HT filling conditions, and electrolytes. The optimally obtained hybrid Solar Cells exhibited 1.5% power-conversion efficiency under AM 1.5G of 100 mW/cm(2) intensity. The fabricated hybrid Cells exhibited highly durable Cell performances, even after 1 month under atmospheric conditions, whereas the liquid junction quantum dot sensitized Solar Cells exhibited a significant degradation in their performances during the first 2 weeks immediately after fabrication. High open-circuit voltage and fill factor values of our hybrid quantum-dot-sensitized Solar Cell indicate that the applied hole transport layer efficiently dissociates electron/hole pairs at the interface and retards the interfacial charge recombination.
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highly efficient and durable quantum dot sensitized zno Nanowire Solar Cell using noble metal free counter electrode
Journal of Physical Chemistry C, 2011Co-Authors: Minsu Seol, Easwaramoorthi Ramasamy, Jinwoo Lee, Kijung YongAbstract:A highly efficient quantum dot sensitized Solar Cell has been fabricated using a CdSe/CdS cosensitized ZnO Nanowire array as a photoelectrode (PE), ordered mesoCellular carbon foam (MSU-F-C) as a counter electrode (CE), and a polysulfide electrolyte as a hole transporter. The Nanowire structure provides efficient photoelectron collection and light harvesting, and CdSe/CdS cosensitization allows utilization of the whole visible wavelength region of the incident Solar spectrum. The MSU-F-C used here provides an extremely high surface area and the ordered large size mesopores with an interconnected pore structure, which facilitate diffusion of redox relay in the electrolyte. As a result, it exhibits low charge transfer resistance (Rct) between the CE/electrolyte interface and thus presents highly efficient photovoltaic performance, compared to conventional noble-metal-based CEs. The Cell with MSU-F-C CE yields the highest power conversion efficiency of 3.60%, with Voc, Jsc, and FF of 685 mV, 12.6 mA/cm2, and...
Erik C. Garnett - One of the best experts on this subject based on the ideXlab platform.
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Fundamentals of the Nanowire Solar Cell: optimization of the open circuit voltage
Applied Physics Reviews, 2018Co-Authors: Jos E. M. Haverkort, Erik C. Garnett, Erik P. A. M. BakkersAbstract:Present day Nanowire Solar Cells have reached an efficiency of 17.8%. Nanophotonic engineering by Nanowire tapering allows for high Solar light absorption. In combination with sufficiently high carrier selectivity at the contacts, the short-circuit current (Jsc) has presently reached 29.3 mA/cm2, reasonably close to the 34.6 mA/cm2 theoretical limit for InP. Although further optimization of the current is important, an equally challenging condition to approach the Shockley Queisser (S-Q) limit is to increase the open-circuit voltage (Voc) towards the radiative limit. The key requirement to reach the radiative limit is to increase the external radiative efficiency at open-circuit conditions towards unity. It is the main purpose of this review to highlight recent progress in nanophotonic engineering to further enhance the open circuit voltage of a Nanowire Solar Cell. In addition to material optimization for increasing the internal photoluminescence efficiency, the light extraction efficiency is a major design criterion for enhancing the external radiative efficiency and thus the Voc. Since the semiconductor substrate is a sink for internally generated photoluminescence, it is equally important to eliminate the loss of emitted light into the substrate. Even at the S-Q limit, the Voc is still substantially decreased by a photon entropy loss due to the conversion of a parallel beam of photons from the sun into an isotropic emission pattern, in which each individual photon is emitted into a random direction. The 46.7% ultimate Solar Cell limit for direct Solar irradiation can only be approached, once the Cell is capable to focus all emitted photoluminescence back to the sun. We will show that nanophotonic engineering provides a pathway to approach the ultimate limit.
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Quantifying losses and thermodynamic limits in nanophotonic Solar Cells
Nature Nanotechnology, 2016Co-Authors: Sander A. Mann, Jos E. M. Haverkort, Erik P. A. M. Bakkers, Sebastian Z. Oener, Alessandro Cavalli, Erik C. GarnettAbstract:Spatially resolved measurements of the absorption, internal quantum efficiency and photoluminescence quantum yield of InP single Nanowire Solar Cells allow the determination of intrinsic losses and thermodynamic limits of these nanophotonic devices. Nanophotonic engineering shows great potential for photovoltaics: the record conversion efficiencies of Nanowire Solar Cells are increasing rapidly^ 1 , 2 and the record open-circuit voltages are becoming comparable to the records for planar equivalents^ 3 , 4 . Furthermore, it has been suggested that certain nanophotonic effects can reduce costs and increase efficiencies with respect to planar Solar Cells^ 5 , 6 . These effects are particularly pronounced in single-Nanowire devices, where two out of the three dimensions are subwavelength. Single-Nanowire devices thus provide an ideal platform to study how nanophotonics affects photovoltaics^ 7 , 8 , 9 , 10 , 11 , 12 . However, for these devices the standard definition of power conversion efficiency no longer applies, because the Nanowire can absorb light from an area much larger than its own size^ 6 . Additionally, the thermodynamic limit on the photovoltage is unknown a priori and may be very different from that of a planar Solar Cell. This complicates the characterization and optimization of these devices. Here, we analyse an InP single-Nanowire Solar Cell using intrinsic metrics to place its performance on an absolute thermodynamic scale and pinpoint performance loss mechanisms. To determine these metrics we have developed an integrating sphere microscopy set-up that enables simultaneous and spatially resolved quantitative absorption, internal quantum efficiency (IQE) and photoluminescence quantum yield (PLQY) measurements. For our record single-Nanowire Solar Cell, we measure a photocurrent collection efficiency of >90% and an open-circuit voltage of 850 mV, which is 73% of the thermodynamic limit (1.16 V).
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Nanowire Solar Cells
Annual Review of Materials Research, 2011Co-Authors: Erik C. Garnett, Mark L. Brongersma, Yi Cui, Michael D McgeheeAbstract:The Nanowire geometry provides potential advantages over planar wafer-based or thin-film Solar Cells in every step of the photoconversion process. These advantages include reduced reflection, extreme light trapping, improved band gap tuning, facile strain relaxation, and increased defect tolerance. These benefits are not expected to increase the maximum efficiency above standard limits; instead, they reduce the quantity and quality of material necessary to approach those limits, allowing for substantial cost reductions. Additionally, Nanowires provide opportunities to fabricate complex single-crystalline semiconductor devices directly on low-cost substrates and electrodes such as aluminum foil, stainless steel, and conductive glass, addressing another major cost in current photovoltaic technology. This review describes Nanowire Solar Cell synthesis and fabrication, important characterization techniques unique to Nanowire systems, and advantages of the Nanowire geometry.
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faceting and disorder in Nanowire Solar Cell arrays
Photovoltaic Specialists Conference, 2010Co-Authors: Evan Pickett, Michael D Mcgehee, Erik C. Garnett, Yi Cui, Yijie Huo, Tomas Sarmiento, Dong Liang, Shruti V. Thombare, Paul C Mcintyre, J S HarrisAbstract:Arrays of semiconductor Nanowires have been discussed as a method of fabricating lower-cost, higher-efficiency Solar Cells [1]. This is accomplished by shortening the minority carrier path to the contacts and by nanoscale light trapping effects [1, 2]. Numerical simulations have played a large role in the development of these Cells [1, 3–5]. However, the approximation of the Nanowire array as a group of uniformly spaced cylinders has limitations, as disorder is often present in fabricated devices. Here, we show that introducing disorder into simulated arrays of semiconductor Nanowires enhances the calculated absorption. Additionally, facets and other surface features serve to reduce reflection and enhance light trapping over the model of the Nanowire as a cylinder. An optimal disorder between 10–20% from uniform is predicted for both cylindrical and hexagonally arranged wires. This effect holds for various semiconductor materials. Preliminary electrical simulations are also presented for Si, GaAs, and Ge Nanowires.
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oligo and polythiophene zno hybrid Nanowire Solar Cells
Nano Letters, 2010Co-Authors: Alejandro L Briseno, Erik C. Garnett, Thomas W Holcombe, Akram Boukai, Steve W Shelton, Jean J M Frechet, Peidong YangAbstract:We demonstrate the basic operation of an organic/inorganic hybrid single Nanowire Solar Cell. End-functionalized oligo- and polythiophenes were grafted onto ZnO Nanowires to produce p−n heterojunction Nanowires. The hybrid nanostructures were characterized via absorption and electron microscopy to determine the optoelectronic properties and to probe the morphology at the organic/inorganic interface. Individual Nanowire Solar Cell devices exhibited well-resolved characteristics with efficiencies as high as 0.036%, Jsc = 0.32 mA/cm2, Voc = 0.4 V, and a FF = 0.28 under AM 1.5 illumination with 100 mW/cm2 light intensity. These individual test structures will enable detailed analysis to be carried out in areas that have been difficult to study in bulk heterojunction devices.
Heejin Kim - One of the best experts on this subject based on the ideXlab platform.
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hybrid type quantum dot cosensitized zno Nanowire Solar Cell with enhanced visible light harvesting
ACS Applied Materials & Interfaces, 2013Co-Authors: Heejin Kim, Hyuncheol Jeong, Chan Eon Park, Kijung YongAbstract:A polymer hybrid quantum-dot-sensitized Solar Cell was developed using CdSe/CdS/ZnO Nanowires as a photoanode and regioregular P3HT as a conjugated polymer. The P3HT polymer was used as a hole tran...
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Hybrid-type quantum-dot cosensitized ZnO Nanowire Solar Cell with enhanced visible-light harvesting
ACS Applied Materials and Interfaces, 2013Co-Authors: Heejin Kim, Hyuncheol Jeong, Tae Kyu An, Chan Eon Park, Kijung YongAbstract:A polymer hybrid quantum-dot-sensitized Solar Cell was developed using CdSe/CdS/ZnO Nanowires as a photoanode and regioregular P3HT as a conjugated polymer. The P3HT polymer was used as a hole transport material to replace the liquid electrolyte in quantum dot sensitized Solar Cells, CdSe/CdS acts as a cosensitizer, which enhances light harvesting in the visible range, and the ZnO Nanowires provide a direct pathway for electron transport. Through an adequate cascade bandgap structure of the photoanode, the photoexcited electrons were effectively separated from the electron/hole pairs and transported under illumination. The remaining holes at the anode were transported by the conjugated polymer P3HT without any intermediate potential loss. The fabrication of the hybrid Solar Cell was optimized with various experimental conditions, including the length of the ZnO Nanowires, quantum sensitizers, P3HT filling conditions, and electrolytes. The optimally obtained hybrid Solar Cells exhibited 1.5% power-conversion efficiency under AM 1.5G of 100 mW/cm(2) intensity. The fabricated hybrid Cells exhibited highly durable Cell performances, even after 1 month under atmospheric conditions, whereas the liquid junction quantum dot sensitized Solar Cells exhibited a significant degradation in their performances during the first 2 weeks immediately after fabrication. High open-circuit voltage and fill factor values of our hybrid quantum-dot-sensitized Solar Cell indicate that the applied hole transport layer efficiently dissociates electron/hole pairs at the interface and retards the interfacial charge recombination.
Nicklas Anttu - One of the best experts on this subject based on the ideXlab platform.
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Absorption of light in a single vertical Nanowire and a Nanowire array
Nanotechnology, 2018Co-Authors: Nicklas AnttuAbstract:Both a single III-V semiconductor Nanowire and an array of such Nanowires have shown promise for Solar Cell applications. However, the correspondence between the optical properties of the single Nanowire and the Nanowire array has not been studied. Here, we perform electromagnetic modeling of InP Nanowires to study this relationship. We find that a single Nanowire can show at an absorption peak, a remarkably high absorption cross-section that is more than 50 times the geometrical cross-section. With optimization of the diameter of the single Nanowire, the short-circuit current density is 30 times higher than in a bulk Solar Cell. With such a strong absorption, we predict an apparent efficiency >500% for the single Nanowire Solar Cell. In contrast, we show that an efficient Nanowire array Solar Cell cannot rely on strong absorption just through the absorption peak. Instead, the Nanowires need to be packed rather closely to enhance the absorption of the full Solar spectrum. At the optimum diameter for the Nanowire array, neighboring Nanowires compete strongly for absorption of incident photons at the absorption peak, which limits the absorption per Nanowire by a factor of 18. As a result, the single InP Nanowire is optimized at a diameter of 110 nm while the Nanowires in the array are optimized at a considerably larger diameter of 180 nm. Importantly, we show analytically the coupling efficiency of incident light into the fundamental HE11 guided mode and consecutive absorption of the mode in the Nanowires. With that analysis, we explain that a single Nanowire shows two different absorption pathways-one through coupling into the guided mode and another by coupling into the Nanowire through the sidewall. This analytical analysis also shows at which period the neighboring Nanowires in an array start to compete for absorption of incident photons.
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gaasp Nanowire Solar Cell development towards Nanowire si tandem applications
2017 IEEE 44th Photovoltaic Specialist Conference (PVSC), 2017Co-Authors: Enrique Barrigón, Nicklas Anttu, Yang Chen, Gaute Otnes, Vilgaile Dagyte, Lars Samuelson, Magnus T. BorgströmAbstract:III - V based Nanowire Solar Cells are a promising candidate to be employed as the top Cell in a III - V/Si tandem structure. Here, we report on the development of p/i/n GaAsP Nanowire Solar Cells with the appropriate bandgap for such tandem structure. The performance of single NW devices is analyzed with current-voltage and electron beam induced current measurements.
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GaAsP Nanowire Solar Cell Development Towards Nanowire/Si Tandem Applications
2017 IEEE 44th Photovoltaic Specialist Conference (PVSC), 2017Co-Authors: Enrique Barrigón, Nicklas Anttu, Yang Chen, Gaute Otnes, Vilgaile Dagyte, Lars Samuelson, Magnus T. BorgströmAbstract:III - V based Nanowire Solar Cells are a promising candidate to be employed as the top Cell in a III - V/Si tandem structure. Here, we report on the development of p/i/n GaAsP Nanowire Solar Cells with the appropriate bandgap for such tandem structure. The performance of single NW devices is analyzed with current-voltage and electron beam induced current measurements.
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Shockley-Queisser Detailed Balance Efficiency Limit for Nanowire Solar Cells
ACS Photonics, 2015Co-Authors: Nicklas AnttuAbstract:III-V semiconductor Nanowire arrays show promise as a platform for next-generation Solar Cells. However, the theoretical efficiency limit for converting the energy of sunlight into electrical energy in such Solar Cells is unknown. Here, we calculate through electromagnetic modeling the Shockley-Queisser efficiency limit for an InP Nanowire array Solar Cell. In this analysis, we calculate first from the absorption of sunlight the short-circuit current. Next, we calculate the voltage-dependent emission characteristics of the Nanowire array. From these processes, we identify how much current we can extract at a given voltage. Finally, after constructing this current-voltage (IV) curve of the Nanowire Solar Cell, we identify from the maximum power output the maximum efficiency. We compare this efficiency of the Nanowire array with the 31.0% efficiency limit of the conventional InP bulk Solar Cell with an inactive substrate underneath. We consider a Nanowire array of 400 nm in period, which shows a high short-circuit current. We optimize both the Nanowire length and diameter in our analysis. For example, Nanowires of 4 mu m in length and 170 nm in diameter produce 96% of the short-circuit current obtainable in the perfectly absorbing InP bulk Cell. However, the Nanowire Solar Cell emits fewer photons than the bulk Cell at thermal equilibrium, especially into the substrate. This weaker emission allows for a higher open circuit-voltage for the Nanowire Cell. As an end result, Nanowires longer than 4 mu m can actually show, despite producing a lower short-circuit current, a higher efficiency limit, of up to 32.5%, than the bulk Cell.
Ze Zhang - One of the best experts on this subject based on the ideXlab platform.
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In situ interface engineering for probing the limit of quantum dot photovoltaic devices
Nature Nanotechnology, 2019Co-Authors: Hui Dong, Xiao Dong Tan, Longbing He, Qiubo Zhang, Yusheng Zhai, Xing Wu, Feng Xu, Ziqi Sun, Tao Xu, Ze ZhangAbstract:In situ investigation of a single Nanowire/quantum dot heterojunction Solar Cell using a custom-designed photoelectric transmission electron microscope set-up reveals the possibility of achieving improved photovoltaic performance.AbstractQuantum dot (QD) photovoltaic devices are attractive for their low-cost synthesis, tunable band gap and potentially high power conversion efficiency (PCE). However, the experimentally achieved efficiency to date remains far from ideal. Here, we report an in-situ fabrication and investigation of single TiO_2-Nanowire/CdSe-QD heterojunction Solar Cell (QDHSC) using a custom-designed photoelectric transmission electron microscope (TEM) holder. A mobile counter electrode is used to precisely tune the interface area for in situ photoelectrical measurements, which reveals a strong interface area dependent PCE. Theoretical simulations show that the simplified single Nanowire Solar Cell structure can minimize the interface area and associated charge scattering to enable an efficient charge collection. Additionally, the optical antenna effect of Nanowire-based QDHSCs can further enhance the absorption and boost the PCE. This study establishes a robust ‘nanolab’ platform in a TEM for in situ photoelectrical studies and provides valuable insight into the interfacial effects in nanoscale Solar Cells.
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In situ interface engineering for probing the limit of quantum dot photovoltaic devices
Nature Nanotechnology, 2019Co-Authors: Hui Dong, Xiao Dong Tan, Longbing He, Qiubo Zhang, Yusheng Zhai, Xing Wu, Feng Xu, Ziqi Sun, Tao Xu, Ze ZhangAbstract:In situ investigation of a single Nanowire/quantum dot heterojunction Solar Cell using a custom-designed photoelectric transmission electron microscope set-up reveals the possibility of achieving improved photovoltaic performance.AbstractQuantum dot (QD) photovoltaic devices are attractive for their low-cost synthesis, tunable band gap and potentially high power conversion efficiency (PCE). However, the experimentally achieved efficiency to date remains far from ideal. Here, we report an in-situ fabrication and investigation of single TiO_2-Nanowire/CdSe-QD heterojunction Solar Cell (QDHSC) using a custom-designed photoelectric transmission electron microscope (TEM) holder. A mobile counter electrode is used to precisely tune the interface area for in situ photoelectrical measurements, which reveals a strong interface area dependent PCE. Theoretical simulations show that the simplified single Nanowire Solar Cell structure can minimize the interface area and associated charge scattering to enable an efficient charge collection. Additionally, the optical antenna effect of Nanowire-based QDHSCs can further enhance the absorption and boost the PCE. This study establishes a robust ‘nanolab’ platform in a TEM for in situ photoelectrical studies and provides valuable insight into the interfacial effects in nanoscale Solar Cells.
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In situ interface engineering for probing the limit of quantum dot photovoltaic devices
'Springer Science and Business Media LLC', 2019Co-Authors: Dong Hui, Xu Feng, Sun Ziqi, Wu Xing, Zhang Qiubo, Zhai Yusheng, Tan, Xiao Dong, He Longbing, Xu Tao, Ze ZhangAbstract:Quantum dot (QD) photovoltaic devices are attractive for their low-cost synthesis, tunable band gap and potentially high power conversion efficiency (PCE). However, the experimentally achieved efficiency to date remains far from ideal. Here, we report an in-situ fabrication and investigation of single TiO2-Nanowire/CdSe-QD heterojunction Solar Cell (QDHSC) using a custom-designed photoelectric transmission electron microscope (TEM) holder. A mobile counter electrode is used to precisely tune the interface area for in situ photoelectrical measurements, which reveals a strong interface area dependent PCE. Theoretical simulations show that the simplified single Nanowire Solar Cell structure can minimize the interface area and associated charge scattering to enable an efficient charge collection. Additionally, the optical antenna effect of Nanowire-based QDHSCs can further enhance the absorption and boost the PCE. This study establishes a robust ‘nanolab’ platform in a TEM for in situ photoelectrical studies and provides valuable insight into the interfacial effects in nanoscale Solar Cells
