Fabrication and Electrical Properties of Si Nanowires Synthesized by Al Catalyzed Vapor−Liquid−Solid Growth

Ke, Yanxiong; Weng, Xiaojun; Redwing, Joan M.; Eichfeld, Chad; Swisher, Thomas R.; Mohney, Suzanne E.; Habib, Y. M.

doi:10.1021/nl902808r

Cited by 74 publications

(80 citation statements)

References 30 publications

(53 reference statements)

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“…Several groups have also postulated that metal nanocluster catalysts, especially gold, used to grow NWs could enhance recombination and adversely affect V OC in NW devices (32) (Fig. S4) as the metal catalyst (32) because Al, unlike Au, does not act as a midband gap trap state in Si (33).…”

Section: Resultsmentioning

confidence: 99%

Coaxial multishell nanowires with high-quality electronic interfaces and tunable optical cavities for ultrathin photovoltaics

Kempa

Cahoon

Kim

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

198

219

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Silicon nanowires (NWs) could enable low-cost and efficient photovoltaics, though their performance has been limited by nonideal electrical characteristics and an inability to tune absorption properties. We overcome these limitations through controlled synthesis of a series of polymorphic core/multishell NWs with highly crystalline, hexagonally-faceted shells, and well-defined coaxial p-type∕ n-type (p∕n) and p∕intrinsic∕n (p∕i∕n) diode junctions. Designed 200-300 nm diameter p∕i∕n NW diodes exhibit ultralow leakage currents of approximately 1 fA, and open-circuit voltages and fillfactors up to 0.5 V and 73%, respectively, under one-sun illumination. Single-NW wavelength-dependent photocurrent measurements reveal size-tunable optical resonances, external quantum efficiencies greater than unity, and current densities double those for silicon films of comparable thickness. In addition, finite-difference-time-domain simulations for the measured NW structures agree quantitatively with the photocurrent measurements, and demonstrate that the optical resonances are due to Fabry-Perot and whispering-gallery cavity modes supported in the high-quality faceted nanostructures. Synthetically optimized NW devices achieve current densities of 17 mA∕cm 2 and power-conversion efficiencies of 6%. Horizontal integration of multiple NWs demonstrates linear scaling of the absolute photocurrent with number of NWs, as well as retention of the high open-circuit voltages and short-circuit current densities measured for single NW devices. Notably, assembly of 2 NW elements into vertical stacks yields short-circuit current densities of 25 mA∕cm 2 with a backside reflector, and simulations further show that such stacking represents an attractive approach for further enhancing performance with projected efficiencies of >15% for 1.2 μm thick 5 NW stacks.nanodevices | nanomaterials | nanophotonics | optical nanocavities | solar cells N anostructures and nanostructured materials may enable next-generation solar cells by providing for efficient charge separation (1-16) and tunable optical absorption (11,(17)(18)(19). Semiconductor nanowires (NWs) have exhibited promising efficiencies as single NW photovoltaic elements (8)(9)(10)(11)(20)(21)(22) and as vertical arrays configured as photovoltaic (23-26) and photoelectrochemical (27, 28) solar cells, where the vertical array has been used to enhance light absorption (29). In the case of Si-based nanostructures, where Si photovoltaics represent benchmark systems with attractive material abundance and cost (30), the efficiency of NW devices has typically been limited by poor electrical performance and lack of tunable control of absorption properties at specific and broadband wavelengths. For example, previous reports of coaxial (8) and axially modulated (9) p-i-n single-NW photovoltaic devices yielded open-circuit voltages (V OC ) below 0.29 V, and, for coaxial devices, large leakage currents >1 pA. Furthermore, to accurately identify potentially unique absorption modes through photocurrent spectra ...

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Section: Resultsmentioning

confidence: 99%

Coaxial multishell nanowires with high-quality electronic interfaces and tunable optical cavities for ultrathin photovoltaics

Kempa

Cahoon

Kim

et al. 2012

Proc. Natl. Acad. Sci. U.S.A.

198

219

View full text Add to dashboard Cite

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“…65 To further investigate this possibility, NWs were synthesized using Al catalyst 65 which, unlike Au, does not act as a mid-band gap trap state in Si. 66 Nevertheless, the best illuminated I-V curve for the core/multi-shell diode geometry ( Figure cm/s, a-SiN x :H provides superior passivation with S << 70 cm/s and a correspondingly very long minority-carrier diffusion length L n >> 30 µm.…”

Section: Device Electrical Transport and Performancementioning

confidence: 99%

Semiconductor nanowires: a platform for exploring limits and concepts for nano-enabled solar cells

Kempa

Day

Kim

et al. 2013

Energy Environ. Sci.

200

133

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Abstract:Over the past decade extensive studies of single semiconductor nanowire and nanowire array photovoltaic devices have explored the potential of these materials as platforms for a new generation of efficient and cost-effective solar cells. This feature review discusses strategies for implementation of semiconductor nanowires in solar energy applications, including advances in complex nanowire synthesis and characterization, fundamental insights from characterization of devices, utilization and control of the unique optical properties of nanowires, and new strategies for assembly and scaling of nanowires into diverse arrays that serve as a new paradigm for advanced solar cells. 2 Table of Contents Entry:Advanced synthetic control over the electronic and optical properties of semiconductor nanowires enables testing new paradigms for advanced solar cells. Broader Context Box:The solar power received by the earth dwarfs global power demands by several orders-ofmagnitude. Photovoltaics convert light to electrical energy and have the potential to partially replace current energy technologies that rely on carbon-based fuels. At present, however, a lack of infrastructure and the high costs of photovoltaics prevent this. New ideas and materials are being explored to develop next-generation solar cells that could operate more efficiently and cheaply. Nanowires have emerged as one promising platform to explore such new concepts.Their small dimensions allow for efficient charge separation and light absorption properties unique as compared to bulk materials. Furthermore, the synthesis and fabrication of nanowire devices differs significantly from traditional wafer-based technologies, thus presenting new opportunities such as use of less abundant materials or cheaper substrates. Here, we discuss the benefits and remaining challenges of nanowires for PV and review progress towards understanding and optimizing the electrical and optical performance of nanowire devices. We focus on single nanowire studies that can define limits for what is achievable when multiple nanowires are assembled. Challenges and initial progress towards scaling are presented, and, for the first time, we articulate unique capabilities of solar cells derived from multiple, distinct NWs. 6

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“…Various methods have been used to synthesize SiNWs, such as laser ablation (LA), thermal evaporation (TE), chemical vapor deposition (CVD), and plasma enhanced chemical vapor deposition (PECVD) [20], [21], [22] and [23].…”

Section: Introductionmentioning

confidence: 99%

Controlling the diameter of silicon nanowires grown using a tin catalyst

Al-Taay

Mahdi

Parlevliet

et al. 2013

Materials Science in Semiconductor Processing

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Silicon nanowires were grown on ITO-coated glass substrates via a pulsed plasma enhanced chemical vapor deposition method, using tin as a catalyst. The thin films of catalyst, with different thicknesses in the range 10-100 nm, were deposited on the substrates by a thermal evaporation method. The effect of the thickness of the thin film catalyst on the morphology of the silicon nanowires was investigated.The scanning/transmission electron microscopy images showed that the wire diameter increased as the thickness of the thin film catalyst increased. The nanowires grown using a thin film thickness of 10 nm were inhomogeneous in diameter, whereas the other thicknesses led to an increase in the homogeneity of the diameters of the nanowires. The dominant wire diameter of the grown silicon nanowires ranged from 70 to 80 nm with 10 nm catalyst thin film thickness, and increased to a range of 190-200 nm with 100 nm catalyst thin film thickness.

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Fabrication and Electrical Properties of Si Nanowires Synthesized by Al Catalyzed Vapor−Liquid−Solid Growth

Cited by 74 publications

References 30 publications

Coaxial multishell nanowires with high-quality electronic interfaces and tunable optical cavities for ultrathin photovoltaics

Coaxial multishell nanowires with high-quality electronic interfaces and tunable optical cavities for ultrathin photovoltaics

Semiconductor nanowires: a platform for exploring limits and concepts for nano-enabled solar cells

Controlling the diameter of silicon nanowires grown using a tin catalyst

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