Modal analysis of enhanced absorption in silicon nanowire arrays

Sturmberg, Björn C. P.; Dossou, Kokou B.; Botten, L. C.; Asatryan, A. A.; Poulton, Christopher G.; Sterke, C. Martijn de; McPhedran, R. C.

doi:10.1364/oe.19.0a1067

Cited by 134 publications

(130 citation statements)

References 44 publications

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“…The commercial Lumerical FDTD Solutions package is used for the simulations performed in this work. Literature on FDTD simulations of NWs has already shown significant reduction in reflection which is attributed to guided modes, Bloch modes and Fabry-Perot resonances [29][30][31]. Furthermore, it is shown that the geometrical properties of the NW arrays (NWAs) strongly influence the emergence of such modes [13].…”

Section: Simulation Of Reflectance and Power Absorptionmentioning

confidence: 99%

Passivation of all-angle black surfaces for silicon solar cells

Rahman

Bonilla

Nawabjan

et al. 2017

Solar Energy Materials and Solar Cells

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Abstract-Optical losses at the front surface of a silicon solar cell have a significant impact on efficiency, and as such, efforts to reduce reflection are necessary. In this work, a method to fabricate and passivate nanowire-pyramid hybrid structures formed on a silicon surface via wet chemical processing is presented. These high surface area structures can be utilised on the front surface of back contact silicon solar cells to maximise light absorption therein. Hemispherical reflectivity under varying incident angles is measured to study the optical enhancement conferred by these structures. The significant reduction in reflectivity (<2%) under low incident angles is maintained at high angles by the hybrid textured surface compared to surfaces textured with nanowires or pyramids alone. Finite Difference Time Domain simulations of these dual micro-nanoscale surfaces under varying angles supports the experimental results. In order to translate the optical benefit of these high surface area structures into improvements in device efficiency, they must also be well passivated. To this end, atomic layer deposition of alumina is used to reduce surface recombination velocities of these ultra-black silicon surfaces to below 30 cm/s. A decomposition of the passivation components is performed using capacitance-voltage and Kelvin Probe measurements. Finally, device simulations show power conversion efficiencies exceeding 21% are possible when using these ultra-black Si surfaces for the front surface of back contact silicon solar cells.

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Section: Simulation Of Reflectance and Power Absorptionmentioning

confidence: 99%

Passivation of all-angle black surfaces for silicon solar cells

Rahman

Bonilla

Nawabjan

et al. 2017

Solar Energy Materials and Solar Cells

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show abstract

“…For nanowire arrays, mode identification is less straight forward, due to the introduction of periodicity; absorption enhancements in nanowire arrays have been attributed to both leaky waveguide modes of individual nanowires [19][20][21][22] and photonic crystal Bloch modes. 12,[23][24][25][26] Previous reports have examined a wide variety of array dimensions, nanowire geometries, and illumination angles, which also exhibit varying dominant mode resonances.…”

Section: Introductionmentioning

confidence: 99%

Resonant absorption in semiconductor nanowires and nanowire arrays: Relating leaky waveguide modes to Bloch photonic crystal modes

Fountaine

Whitney

Atwater

2014

Journal of Applied Physics

108

107

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We present a unified framework for resonant absorption in periodic arrays of high index semiconductor nanowires that combines a leaky waveguide theory perspective and that of photonic crystals supporting Bloch modes, as array density transitions from sparse to dense. Full dispersion relations are calculated for each mode at varying illumination angles using the eigenvalue equation for leaky waveguide modes of an infinite dielectric cylinder. The dispersion relations along with symmetry arguments explain the selectivity of mode excitation and spectral red-shifting of absorption for illumination parallel to the nanowire axis in comparison to perpendicular illumination. Analysis of photonic crystal band dispersion for varying array density illustrates that the modes responsible for resonant nanowire absorption emerge from the leaky waveguide modes.

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“…The array pitch and wire diameter are easily tunable due to the use of patterned masks, created by electron-beam lithography [20] or nanoimprint lithography [22]. Reported light trapping mechanisms include coupling into photonic crystal modes [4,[23][24][25][26], coupling into leaky radial waveguide modes [8,13,15,[27][28][29], and absorption in media considered using effective index models [30,31]. In this paper, we discuss mechanisms for broadband absorption in sparse arrays, where light coupling into localized radial modes dominates over coupling into Bloch-like photonic crystal modes that depend on array periodicity.…”

Section: Introductionmentioning

confidence: 99%

Near-unity broadband absorption designs for semiconducting nanowire arrays via localized radial mode excitation

Fountaine

Kendall²,

Atwater³

2014

Opt. Express

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Abstract:We report design methods for achieving near-unity broadband light absorption in sparse nanowire arrays, illustrated by results for visible absorption in GaAs nanowires on Si substrates. Sparse (<5% fill fraction) nanowire arrays achieve near unity absorption at wire resonant wavelengths due to coupling into 'leaky' radial waveguide modes of individual wires and wire-wire scattering processes. From a detailed conceptual development of radial mode resonant absorption, we demonstrate two specific geometric design approaches to achieve near unity broadband light absorption in sparse nanowire arrays: (i) introducing multiple wire radii within a small unit cell array to increase the number of resonant wavelengths, yielding a 15% absorption enhancement relative to a uniform nanowire array and (ii) tapering of nanowires to introduce a continuum of diameters and thus resonant wavelengths excited within a single wire, yielding an 18% absorption enhancement over a uniform nanowire array.

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Modal analysis of enhanced absorption in silicon nanowire arrays

Cited by 134 publications

References 44 publications

Passivation of all-angle black surfaces for silicon solar cells

Passivation of all-angle black surfaces for silicon solar cells

Resonant absorption in semiconductor nanowires and nanowire arrays: Relating leaky waveguide modes to Bloch photonic crystal modes

Near-unity broadband absorption designs for semiconducting nanowire arrays via localized radial mode excitation

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