All‐Angle Invisibility Cloaking of Contact Fingers on Solar Cells by Refractive Free‐Form Surfaces

Schumann, Martin; Langenhorst, Malte; Smeets, Michael; Ding, Kaining; Paetzold, Ulrich W.; Wegener, Martin

doi:10.1002/adom.201700164

Cited by 29 publications

(25 citation statements)

References 16 publications

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“…As a comparison, Ho et al showed a 3% increase in the EQE with increased incident angle using nanoparticle surface coatings . Schumann et al attained a 7.6% increase in the short circuit current using refractive surfaces . We show that the EQE and current output of the solar cell can be enhanced, both at normal incidence as well as over a wide angular range, by as much as 10% and 20%, respectively, the latter of which is critical for increasing total energy conversion in solar cells over the course of a day and across seasons.…”

Section: Introductionmentioning

confidence: 58%

“…A particularly attractive materials‐based approach is to engineer the encapsulation material (typically made from either polymer resins or glass), whereby specifically designed and fabricated optical structures manage the transmission of light to maximize delivery to the active regions of the cell. Examples include coatings, diffraction and diffuse layers, geometric optical structures, cloaking schemes, as well as light‐guiding mechanisms…”

Section: Introductionmentioning

confidence: 99%

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Enhanced Wide‐Angle Energy Conversion Using Structure‐Tunable Waveguide Arrays as Encapsulation Materials for Silicon Solar Cells

Biria

Chen

Hosein

2018

Physica Status Solidi (a)

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The authors report on the enhancement in optical energy conversion in silicon solar cells encapsulated with a polymer film comprising of waveguide array structures. The structures are fabricated through light-induced selfwriting with periodic arrangements of optical beams transmitted through a binary component photopolymer, wherein a periodic core-cladding architecture is produced. The size, spacing, and arrangement of the cores are varied through the size and arrangement of the optical beams via photomask design. A range of waveguide array structures are produced using different masks and component weight fractions. External quantum efficiency (EQE) measurements reveal structures that provide the greatest enhancement for normal and non-normal incidence irradiation, the latter for which reveals wide-angle light capture and conversion. Encapsulated solar cells yield an approximate 10% enhancement in EQE and a 20% increase in the short circuit current, up to an incident angle of 40 , as compared to uniform encapsulants. The experimental results are corroborated by beam propagation simulations that show the spatial confinement of transmitted optical energy is the main effect that increases conversion efficiency. Principles that establish a structure-property-performance relationship are discussed, toward rational materials processing to increase energy conversion.

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Section: Introductionmentioning

confidence: 58%

Section: Introductionmentioning

confidence: 99%

Enhanced Wide‐Angle Energy Conversion Using Structure‐Tunable Waveguide Arrays as Encapsulation Materials for Silicon Solar Cells

Biria

Chen

Hosein

2018

Physica Status Solidi (a)

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“…However, a recent development in optical engineering could significantly change the discussion, namely, the use of 3D surface contouring and/or refractive index grading of transparent polymers via direct laser writing to optically cloak the metallic lines—bending light around the electrodes and effectively making them invisible to the solar cell ( Figure 18 ). This strategy allows a majority of the photocurrent lost to shadowing to be regained in addition to providing some environmental encapsulation. When employed in carbon nanotube–silicon solar cells along with effective AR, this can limit optical losses to being solely those of the nanotube film absorption features which, as previously described, can be engineered to a minimum of just a few percent in the range of silicon's absorption.…”

Section: Improving Performancementioning

confidence: 99%

Advances in Carbon Nanotube–Silicon Heterojunction Solar Cells

Tune

Flavel

2018

Advanced Energy Materials

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in this field as represented in Figure 2 and is broadly divided into two halves. The first half presents some essential background information on carbon nanotubes, particularly in relevance to their role in these kinds of solar cells, as well as a consideration of aspects such as thin film properties, device stability, scale-up, and operating mechanism, while the second half deals with the factors involved in improving performance.This review has been constrained almost exclusively to covering developments in the field of carbon nanotubes interfaced with monocrystalline silicon, though the field is also informed by other work being done in the associated areas of graphene-silicon and conducting polymer-silicon solar cells, as well as the use of nanotube films interfaced with polycrystalline silicon and other semiconductors, perovskites, organic photovoltaics, and more. This is partly in the interests of being able to provide a useful and informative level of technical detail while keeping the work to a manageable and digestible size both for those already working in the field and those new to it. It is also because although there are many parallels between, for example, the nanotube-silicon and polymer-silicon or graphene-silicon works, there are several important and fundamental differences, not the least of which may be the potential complexity/diversity of the operating mechanism(s) in the nanotube-silicon case. For information on these and other related types of photovoltaic device architectures incorporating carbon nanotubes, we refer the reader to Zielke et al., [49] Wang et al., [50] and Arnold et al., [51] as well as Li et al. [52] which also includes an overview of the carbon nanotube-silicon architecture as a part of the broader carbon-silicon theme. Table S1 of the Supporting Information provides a detailed and comprehensive list of published works in the carbon nanotube-silicon field along with various performance measurements, device structure parameters, and material properties. BackgroundAlthough once an exotic, poorly understood, and difficult to obtain material, carbon nanotubes are now relatively well known, well understood, and widely available from commercial suppliers. Briefly, single-walled carbon nanotubes (SWCNT) are very high aspect ratio cylinders of graphene in which the Heterojunctions of carbon nanotubes interfaced with silicon respond to light illumination and can be operated in the power regime as solar cells. Very significant advances have been made in the last 5 years both in terms of headline performance values and in fundamental understanding of the underlying operating principles, as well as the sophistication of the devices and studies being reported. The body of literature is growing rapidly, and the latest power conversion efficiency and active area records have now reached over 17% and 2 cm 2 , respectively. Thus, the authors believe that it is now a useful time for an evaluation of the current state-of-the-art and challenges going forward, as well as for a comprehensively ...

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“…These include the use of lossy metals instead of PEC for the rear contact and back-reflector, power loss in the emitter region due to sheet resistance and increased surface recombination velocity. We do not explicitly consider shadowing loss of the front contacts given recent advances in broad-band, wide-angle cloaked-contacts [34][35][36][37] and interdigitated back contacts (IBC) [5,[30][31][32].…”

Section: Practical Considerationsmentioning

confidence: 99%

“…Accurate simulation of an IBC cell would require at least a 2D transport model for photo-generated charge carriers [33]. The second approach is the application of a dielectric coating over the contacts that effectively "cloaks" them by refracting nearly all incident sunlight "around" the metal fingers [34][35][36][37].…”

Section: Introductionmentioning

confidence: 99%

Designing High-Efficiency Thin Silicon Solar Cells Using Parabolic-Pore Photonic Crystals

Bhattacharya

John

2018

Phys. Rev. Applied

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We demonstrate the efficacy of wave-interference based light-trapping and carrier transport in parabolic-pore photonic crystal, thin-crystalline silicon (c − Si) solar cells to achieve above 29% power conversion efficiencies. Using rigorous solution of Maxwell's equations through a standard finite difference time domain (FDTD) scheme, we optimize the design of the vertical-parabolic-pore photonic crystal (PhC) on a 10 µm thick c − Si to obtain a maximum achievable photocurrent density (MAPD) of 40.6 mA/cm 2 , beyond the ray optics, Lambertian light-trapping limit. For a slanted-parabolic-pore PhC, that breaks x − y symmetry, improved light-trapping occurs due to better coupling into parallel-to-interface refraction (PIR) modes. We achieve optimum MAPD of 41.6 mA/cm 2 for a tilt angle of 10 • with respect to the vertical axis of the pores. This MAPD is further improved to 41.72 mA/cm 2 by introducing a 75 nm SiO2 anti-reflection coating (ARC) on the top of the solar cell. We use this MAPD and associated charge-carrier generation profile as input for numerical solution of the Poisson's equation coupled with semiconductor drift-diffusion equations using a Shockley-Read-Hall and Auger recombination model. Using experimentally achieved surface recombination velocities of 10 cm/s, we identify semiconductor doping profiles that yield power conversion efficiency over 29%. Practical considerations of additional upper-contact losses suggest efficiencies close to 28%. This improvement beyond the current world record is largely due to an open-circuit voltage approaching 0.8 V enabled by reduced bulk recombination in our thin-silicon architecture while maintaining a high short-circuit current through wave-interference-based lighttrapping.

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All‐Angle Invisibility Cloaking of Contact Fingers on Solar Cells by Refractive Free‐Form Surfaces

Cited by 29 publications

References 16 publications

Enhanced Wide‐Angle Energy Conversion Using Structure‐Tunable Waveguide Arrays as Encapsulation Materials for Silicon Solar Cells

Enhanced Wide‐Angle Energy Conversion Using Structure‐Tunable Waveguide Arrays as Encapsulation Materials for Silicon Solar Cells

Advances in Carbon Nanotube–Silicon Heterojunction Solar Cells

Designing High-Efficiency Thin Silicon Solar Cells Using Parabolic-Pore Photonic Crystals

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