InP Nanowire/Polymer Hybrid Photodiode

Novotny, Clint J.; Yu, Edward T.; Yu, Paul K. L.

doi:10.1021/nl072372c

Cited by 167 publications

(116 citation statements)

References 26 publications

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“…We note that surface passivation of InP nanowires may yet be advantageous for light emission applications and photodiode devices, as demonstrated in previous studies. 5,18,19 To further examine the carrier lifetimes, we performed room temperature time-resolved PL measurements using a PL upconversion setup described in the Supporting Information. The sample was excited at 736 nm with pulses of 100 fs duration.…”

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confidence: 99%

Ultralow Surface Recombination Velocity in InP Nanowires Probed by Terahertz Spectroscopy

et al. 2012

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Using transient terahertz photoconductivity measurements, we have made noncontact, room temperature measurements of the ultrafast charge carrier dynamics in InP nanowires. InP nanowires exhibited a very long photoconductivity lifetime of over 1 ns, and carrier lifetimes were remarkably insensitive to surface states despite the large nanowire surface area-to-volume ratio. An exceptionally low surface recombination velocity (170 cm/s) was recorded at room temperature. These results suggest that InP nanowires are prime candidates for optoelectronic devices, particularly photovoltaic devices, without the need for surface passivation. We found that the carrier mobility is not limited by nanowire diameter but is strongly limited by the presence of planar crystallographic defects such as stacking faults in these predominantly wurtzite nanowires. These findings show the great potential of very narrow InP nanowires for electronic devices but indicate that improvements in the crystallographic uniformity of InP nanowires will be critical for future nanowire device engineering. KEYWORDS: InP, nanowire, terahertz, photoconductivity, surface recombination velocity, mobility S emiconductor nanowires are predicted to drive new generations of compact, ultrafast, and high efficiency electronic and optoelectronic devices. Among nanowire materials, InP is especially promising due to its direct band gap and high electron mobility. A multitude of prototype InP nanowire devices have been demonstrated including photodetectors, 1 light-emitting diodes, 2 waveguides, 3 solar cells, 4,5 and field effect transistors. 2,6 Despite these early successes, there remain many fundamental unanswered questions concerning the dynamics of charge carriers in nanowires, and the effects of nanowire size, surfaces, and crystal structure on nanowire electronic properties. A greater understanding of these effects is essential for the future engineering of nanowirebased devices.In this Letter, we examine the ultrafast carrier dynamics within InP nanowires and assess the effects of nanowire diameter, surfaces, and crystal structure. These investigations were performed using optical pump−terahertz probe (OPTP) spectroscopy, a technique which is ideally suited for nanowire studies because it is a noncontact ultrafast probe of room temperature photoconductivity with subpicosecond resolution. 7The contact-free nature of this technique confers a significant advantage over conventional electrical transport measurements, which are subject to artifacts associated with electrical contacts and the models used to extract data. 8,9 A further advantage is that the OPTP measurements are performed at room temperature, so its measurements of carrier mobility and lifetime are directly relevant to future InP nanowire-based devices which will be operated at room temperature.From OPTP measurements on InP nanowires of different diameters, we determine that surface recombination is negligible in InP nanowires. This result is despite the large surface area-to-volume rati...

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Ultralow Surface Recombination Velocity in InP Nanowires Probed by Terahertz Spectroscopy

et al. 2012

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“…15 Semiconductor nanowires (NWs) with high aspect ratio are particularly attractive for use in hybrid solar cells because they offer direct charge pathways to electrodes, large surface areas, high carrier mobility along the nanowires, and chemical and physical stability. 1,3,10,12,16,17 However, the charge transport in such nanowires has been shown to be strongly affected by the presence of surface defect states 18−20 that act as charge traps. A number of methods have therefore been devised to passivate such traps, including overgrowing the NWs surface with a layer of largebandgap semiconductor 18,21 or treatment with sulfides.…”

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Strong Carrier Lifetime Enhancement in GaAs Nanowires Coated with Semiconducting Polymer

et al. 2012

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ABSTRACT:The ultrafast charge carrier dynamics in GaAs/ conjugated polymer type II heterojunctions are investigated using time-resolved photoluminescence spectroscopy at 10 K. By probing the photoluminescence at the band edge of GaAs, we observe strong carrier lifetime enhancement for nanowires blended with semiconducting polymers. The enhancement is found to depend crucially on the ionization potential of the polymers with respect to the Fermi energy level at the surface of the GaAs nanowires. We attribute these effects to electron doping by the polymer which reduces the unsaturated surfacestate density in GaAs. We find that when the surface of nanowires is terminated by native oxide, the electron injection across the interface is greatly reduced and such surface doping is absent. Our results suggest that surface engineering via π-conjugated polymers can substantially improve the carrier lifetime in nanowire hybrid heterojunctions with applications in photovoltaics and nanoscale photodetectors.

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“…Evidently, the ZnO NWs are better charge conductors than PCBM, and also contribute positively to J sc [31]. Hybrid structures of InP NWs and P3HT have also been tried as photodiodes with good FF (~0.44) but low J sc [32]. Here, the n-InP NWs were grown on indium tin oxide electrodes and enveloped with p-type P3HT.…”

Section: Photovoltaicsmentioning

confidence: 99%

Energy production and conversion applications of one-dimensional semiconductor nanostructures

Chattopadhyay¹,

Chen

2011

NPG Asia Mater

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W ith the projected world demand for energy reaching 612 quadrillion Btu (~649×10 18 J or 33 GW-yrs) in 2020 and the associated problem of carbon emission, it has become necessary to look for every enabling technology that may assist in reaching that goal in a sustainable way. Th is daunting task can broadly be classifi ed into two areas of research. Th e fi rst area includes enhancing the effi ciencies of existing 'power-consuming' technologies as well as energy generation and conversion. For example, the use of light-emitting diodes (LEDs) may push external effi ciencies up to 50%, against 13% for conventional technologies such as fl uorescent lamps. Th e use of sustainable energy generation by solar photovoltaics not only contributes to energy supply but also controls carbon emission. Th e second area includes efficient energy-storage systems, such as fuel cells and lithium batteries, for the portable electronic devices that continue to percolated throughout human society.Th e advent of nanoscience has shed light on almost every fi eld of science and technology, particularly in the development of renewable energies. Among the vast varieties of nanomaterials that have been developed, onedimensional (1D) nanomaterials with their inherent large specifi c surface areas and continuous transport path for charge carriers are useful for energy harvesting and conversion applications, which are mostly associated with surface reaction and carrier transport. When the diameter of a material is reduced below a critical value, the additional advantage of 1D materials, such as surface band bending-enhanced photoconductivity or even ballistic transport, may appear, which further enhances their carrier transport properties and hence energy conversion effi ciency. Extensive investigations have been made in this direction aiming to enhance the effi ciency of energy conversion and harvesting while lowering the cost of the aforementioned devices. In this review, selected 1D nanomaterials and their applications in energy conversion and generation technologies such as photonics, photovoltaics, photocatalysis and fuel cells will be covered. Solid-state lighting and LEDsIncreased technology effi ciency will eventually lower the demand for energy. For example, approximately 20% of world energy demand is for lighting purposes, which can be reduced through the effi cient use of LEDs instead of the fl uorescent, incandescent or high-pressure discharge lamps commonly used today. Group III nitride materials such as AlN, GaN and InN dominate in the fi eld of LEDs. However, ternary and quaternary compounds arising out of a mix of these, for example Al x Ga 1-x N and In x Ga 1-x N, can have their bandgaps, and hence emission, tuned from deep ultraviolet (UV) to the infrared by adjusting the composition fraction x [1]. Th ese materials are hard to grow due to the scarcity of lattice-matched substrates, which has led to defects in the crystal that deteriorate the device's optoelectronic properties. One-dimensional nanowires (NWs), on the other h...

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InP Nanowire/Polymer Hybrid Photodiode

Cited by 167 publications

References 26 publications

Ultralow Surface Recombination Velocity in InP Nanowires Probed by Terahertz Spectroscopy

Ultralow Surface Recombination Velocity in InP Nanowires Probed by Terahertz Spectroscopy

Strong Carrier Lifetime Enhancement in GaAs Nanowires Coated with Semiconducting Polymer

Energy production and conversion applications of one-dimensional semiconductor nanostructures

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