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Synergy effect of carbon nanotube and graphene hydrogel on highly efficient quantum dot sensitized solar cells
摘要： Carbon based composite counter electrodes (CEs) containing metal sulfides have shown excellent catalytic activity in quantum dot sensitized solar cells (QDSCs), but the series resistance of the device is still greatly larger than that of brass based CEs of CuxS/brass. In this work, carbon nanotubes (CNTs) are incorporated into the binary system of graphene hydrogel (GH) and copper sulfide (CuS) during gelation to form CNT-GH-CuS composite CEs. Results show that the ternary CEs exhibit greatly higher conductivity than that of binary CNT-CuS and GH-CuS CEs, and the series resistance dramatically drops from ~ 3 to 0.79 ? which is similar to that of CuxS/brass CEs. Due to the improved conductivity, catalytic activity and intimate contact with substrate, the assembled Zn-Cu-In-Se QDSCs receive a record power conversion efficiency of 14.02%.
关键词： Counter electrode,copper sulfide,solar cell,carbon nanotube,graphene hydrogel
更新于2025-09-16 10:30:52
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Model for electroluminescence in single-walled carbon nanotube field effect transistor under transverse magnetic field
摘要： Electroluminescence spectrum and radiative recombination rate of short channel single-walled carbon nanotube field effect transistor in presence of transverse magnetic field is calculated by using non-equilibrium Green’s function method. Significant enhancement in radiative recombination rate and red shift in electroluminescence spectrum are observed with increase in the strength of magnetic field. The band gap suppression estimated from energy position resolved local density of states calculation plays a dominant role in transport mechanism under the influence of external magnetic field. The tuning of electroluminescence spectrum of single-walled carbon nanotube by transverse magnetic field can be employed as nanoscale optical source in next generation optoelectronic and photonic devices.
关键词： electroluminescence,single-walled carbon nanotube,optoelectronics,radiative recombination rate,plasmonics,field effect transistor
更新于2025-09-16 10:30:52
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Ideal <i>pn</i> Diodes from Single-Walled Carbon Nanotubes for Use in Solar Cells: Beating the Detailed Balance Limit of Efficiency
摘要： Though many technologies exist for improving solar cell efficiencies, there remains an unexplored fundamental parameter, the diode ideality factor (??), that we can exploit. The Shockley-Queisser limit states that the maximum solar conversion efficiency in a single pn junction is achievable only when it is operated in the ideal diode limit of ?? = 1. Generation and recombination losses correlate directly to an increase in the dark saturation current and ??, both of which have competing effects on the open-circuit voltage. Here, we demonstrate a new approach to improving the efficiency of solar cells beyond the detailed balance limit by gate modulation of the diode’s ideality factor in ideal carbon nanotube pn diodes. We show that the open-circuit voltage can be tuned in direct proportion to ?? without impacting the reverse bias leakage current or the short circuit current. We show that our approach is similar to the enhancement from solar concentrators without actually using them. We achieve an open-circuit voltage that is ~300% higher than that given by the detailed balance limit.
关键词： pn junction,photovoltaic effect,open-circuit voltage,gate-tunable diodes,Single-walled carbon nanotube,detailed balance limit
更新于2025-09-16 10:30:52
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Fiber Laser || Passive Q-switched and Mode-locked Fiber Lasers Using Carbon-based Saturable Absorbers
摘要： This chapter aims to familiarize readers with general knowledge of passive Q-switched and mode-locked fiber lasers. It emphasizes on carbon-based saturable absorbers, namely graphene and carbon nanotubes (CNTs); their unique electronic band structures and optical characteristics. The methods of incorporating these carbon-based saturable absorbers into fiber laser cavity will also be discussed. Lastly, several examples of experiments where carbon-based saturable absorbers were used in generating passive Q-switched and mode-locked fiber lasers are demonstrated.
关键词： passive Q-switch,graphene,carbon nanotube,Fiber laser,passive mode-lock
更新于2025-09-16 10:30:52
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[IEEE 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Chicago, IL, USA (2019.6.16-2019.6.21)] 2019 IEEE 46th Photovoltaic Specialists Conference (PVSC) - Modeling Methodology for Determining Energy Collection Potential of Photovoltaics Applied To Curved Surfaces
摘要： Arrays of periodic one-dimensional nanomaterials offer tunable optical properties in terms of light–matter interaction which are attractive for designing efficient optoelectronic devices. This paper presents a fabrication of bottom-up grown nanopillar (NP) array solar cells based on n-i-p thin-film amorphous silicon using scaffolds of vertically aligned carbon nanotube (CNT) array. The effects of varying the CNT spacing over the range from 800 to 2000 nm on optical and electrical properties of the solar cells were investigated. The NP solar cell with CNT spacing of 800 nm exhibited ‘moth-eye’ broadband antireflection behavior, showing an average reflectance value lower than 10%. The enhanced optical absorption translated to significant enhancements in photocurrent and quantum efficiency compared to a conventional planar solar cell under low light condition. The open-circuit voltage (Voc) of the NP solar cell was found systematically correlated with the CNT spacing and the illumination condition. The results presented here is of importance for developing high efficiency one-dimensional nanostructured solar cells.
关键词： photovoltaic cells,nanostructured materials,nanophotonics,Amorphous silicon,carbon nanotube (CNT)
更新于2025-09-16 10:30:52
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Semiconducting single-walled carbon nanotube/graphene van der Waals junctions for highly sensitive all-carbon hybrid humidity sensors
摘要： Van der Waals (vdW) heterojunctions composed of diverse atomic-thin nanomaterials have great potential as building blocks for innovative nanodevices due to the unique electron coupling effect. However, previous researches have mainly focused on the light-mater interactions and charge transfer process, and the interactions between gas/vapor and vdW heterojunctions still remain to be verified. Herein, we firstly demonstrate the charge transfer based on the interaction between water (H2O) molecules and the all-carbon vdW junctions, which are formed by stacking non-carboxylated (6, 5) single-walled carbon nanotube (SWCNT) on the surface of chemical vapor deposition synthesized graphene. Based on these interaction mechanism and charge transfer process, a proof-of-concept all-carbon vdW junction humidity sensor has been fabricated. The device exhibits good reproducibility and high sensitivity of 24% per 1% RH change in a wide relative humidity range of 5~80 % with short response/recovery time of 198/110 ms. Furthermore, the effect of H2O molecule absorption on the charge transfer dynamics at the SWCNT/graphene vdW junctions has been demonstrated via Raman spectra, giving a novel humidity sensing mechanism. Our finding provides a new strategy to fabricate high performance humidity sensors using vdW heterojuctions as sensing layers.
关键词： humidity sensor,single-walled carbon nanotube,graphene,charge transfer,van der Waals heterojunctions
更新于2025-09-16 10:30:52
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Polarized Raman imaging of large area aligned semiconducting single‐walled carbon nanotubes
摘要： The current method of characterizing single-walled carbon nanotube (SWCNT) alignment utilizes single-point measurements of a few hundred square nanometers of polarized Raman spectroscopy to characterize an entire substrate of SWCNTs on the order of square centimeters. In this study, we demonstrate a new polarized Raman spectroscopy analyzation technique of orientation Raman imaging that images areas as large as 1 mm2. This provides a significantly more accurate representation of the spatial distribution in the alignment of any SWCNT film by increasing the measured area by 10 orders of magnitude over previous standard characterization techniques. Furthermore, this creates an “easy-to-see” visual representation of alignment based on optical anisotropy values. Improving the efficiency of characterizing alignment in SWCNT films via polarized Raman spectroscopy is an important step toward manufacturing scalable films of aligned SWCNTs.
关键词： polarized Raman imaging,polarized Raman spectroscopy,orientation image,carbon nanotube alignment,carbon nanotubes
更新于2025-09-12 10:27:22
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Porous single-wall carbon nanotube templates decorated with all-inorganic perovskite nanocrystals for ultra-flexible photodetectors
摘要： As an inevitable optoelectronic material with unique properties, halide perovskites attracted increasing attention in recent years. Meanwhile, hybridization of nanostructured perovskites with one-dimensional (1D) or two-dimensional (2D) functional materials has exhibited unique applications in nanotechnology. In this communication, a highly conducting porous single-wall carbon nanotube (p-SWCNT) template decorated with phase-pure CsPbBr3 nanocrystals by simple solution-phase technique was demonstrated, and the ultra-flexible photodetector Au/p-SWCNT:CsPbBr3/Au showed high sensitivity even in highly bending state. Also, the mechanism of wetting CsPbBr3 along p-SWCNT and the detailed fabrication process for ultra-flexible photodetectors were highlighted. The direct contact (in-situ) on p-SWCNT by crystallization of perovskite precursor can enhance the charge transfer at their interface effectively. At applied bias of +5 V, the optimized photodetector Au/p-SWCNT:CsPbBr3/Au exhibits a maximum photoresponsivity of 41.0 AW-1 with a specific detectivity of 1.67×1012 Jones under an incident 232 μW/cm2 520 nm illumination. In addition, it exhibits excellent mechanical and electrical properties even under high strain (i.e. bending angle up to -17°) and recovers the original performance after repeated bending cycles upto 1000 times. Our experimental results showed that such a hybrid materials provide a promising method for rigid and flexible optoelectronic devices.
关键词： Porous single-wall carbon nanotube (p-SWCN),inorganic perovskite nanocrystals,flexible photodetector,CsPbBr3,visible light photodetector
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Stochastic Soliton Quantization in Mode-Locked Fibre Laser
摘要： Soliton quantization is a natural, intrinsic and random consequence property of localized pulses in nonlinear systems. It is formed in the fiber laser in the form of dissipative solitons due to the gain competition between the solitons in the laser cavity. The observation of quantized separations between the solitons was predicted either due to the interaction between far separated solitons or due to the interaction between weakly overlapping pulses [1, 2]. It was first found experimentally in a nonlinear amplified loop mirror mode-locked fiber laser [3] and then in a nonlinear polarization rotation mode locking fiber laser [4, 5] with a requirement of high pump power of >400 mW. Here, we report for the first time the experimental demonstration of the stochastic temporal soliton quantization state regimes at a low range of the pump powers (~41 mW) using a carbon nanotube’s saturable absorber mode-locked fiber laser [6]. We found that the regimes and the total number of pulses in the cavity are highly sensitive to the pump power and the state of the polarization which could lead to several distinct regimes of pulse formation. However, for certain pumping powers which were 41 mW and specific orientation of the laser cavity polarization controller (PC), we observed pulse trains of several tenths of pulses as shown in the real-time spatiotemporal measurements in Fig. 1a. The pulse train consists of a stochastic quantized distribution with separation between pulses starting from about 3 ns to tenths of ps with a nonlinearly quantized separation, behaving between the localized soliton pulses as shown in Fg. 1b. The pulses are localized with a much broader temporal separation far from the main soliton pulse and condensed to a very narrow seperations nearer to it. By slightly increasing the pump power to ~88 mW and varying the PC, we obtained the second order of the stochastic soliton which also have a quantized temporal distribution without any undesirable distribution of types or interactions between neighboring solitons along 5000 roundtrip pulse train. The quantized soliton, actually, has formed intrinsically in the form of dissipative solitons due to large binding soliton states.
关键词： Soliton quantization,stochastic soliton,carbon nanotube saturable absorber,mode-locked fibre laser
更新于2025-09-12 10:27:22
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Counting statistics of dark-state transport through a carbon nanotube quantum dot
摘要： In a recent experiment [A. Donarini et al., Nat. Commun. 10, 381 (2019)], electronic transport through a carbon nanotube quantum dot was observed to be suppressed by the formation of a quantum-coherent “dark state.” In this paper we consider theoretically the counting statistics and waiting-time distribution of this dark-state-limited transport. We show that the statistics are characterized by giant super-Poissonian Fano factors and long-tailed waiting-time distributions, both of which are signatures of the bistability and extreme electron bunching caused by the dark state.
关键词： carbon nanotube quantum dot,super-Poissonian Fano factors,dark state,counting statistics,waiting-time distribution
更新于2025-09-12 10:27:22