Realization and evaluation of diffractive systems on the back side of silicon solar cells

Berger, Pauline; Hauser, Hubert; Suwito, Dominik; Janz, S.; Peters, Ian Marius; Bläsi, Bénédikt; Hermle, Martin

doi:10.1117/12.854553

Cited by 13 publications

(10 citation statements)

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“…This implies the added assumption that the cladding region is thicker than the coherence length of the incident solar radiation ( SK 1 urn). It has been shown that thicker cladding regions are desirable due to reduced parasitic absorption in the rear reflector [9,12].…”

Section: Cell Typesmentioning

confidence: 99%

A numerical study of Bi-periodic binary diffraction gratings for solar cell applications

Mellor

Tobias

Martı́

et al. 2011

Solar Energy Materials and Solar Cells

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Keywords: Diffraction grating Absorption enhancement Light trapping Surface texturing Intermediate band solar cellIn this paper, a numerical study is made of simple bi-periodic binary diffraction gratings for solar cell applications. The gratings consist of hexagonal arrays of elliptical towers and wells etched directly into the solar cell substrate. The gratings are applied to two distinct solar cell technologies: a quantum dot intermediate band solar cell (QD-IBSC) and a crystalline silicon solar cell (SSC). In each case, the expected photocurrent increase due to the presence of the grating is calculated assuming AM1.5D illumination. For each technology, the grating period, well/tower depth and well/tower radii are optimised to maximise the photocurrent. The optimum parameters are presented. Results are presented for QD-IBSCs with a range of quantum dot layers and for SSCs with a range of thicknesses. For the QD-IBSC, it is found that the optimised grating leads to an absorption enhancement above that calculated for an ideally Lambertian scatterer for cells with less than 70 quantum dot layers. In a QD-IBSC with 50 quantum dot layers equipped with the optimum grating, the weak intermediate band to conduction band transition absorbs roughly half the photons in the corresponding sub-range of the AM1.5D spectrum. For the SSC, it is found that the optimised grating leads to an absorption enhancement above that calculated for an ideally Lambertian scatterer for cells with thicknesses of 10 um or greater. A 20 um thick SSC equipped with the optimised grating leads to an absorption enhancement above that of a 200 lira thick SSC equipped with a planar back reflector.

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Section: Cell Typesmentioning

confidence: 99%

A numerical study of Bi-periodic binary diffraction gratings for solar cell applications

Mellor

Tobias

Martı́

et al. 2011

Solar Energy Materials and Solar Cells

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“…Diffraction gratings were first proposed for thin-film solar cells by Sheng et al [2], and later for wafer-based solar cells by Heine and Morf [3]. More recent studies of wafer-based applications can be found in [4,5].…”

Section: Introductionmentioning

confidence: 99%

Nanoimprinted diffraction gratings for crystalline silicon solar cells: implementation, characterization and simulation

Mellor¹,

Hauser²,

Wellens³

et al. 2013

Opt. Express

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Light trapping is becoming of increasing importance in crystalline silicon solar cells as thinner wafers are used to reduce costs. In this work, we report on light trapping by rear-side diffraction gratings produced by nano-imprint lithography using interference lithography as the mastering technology. Gratings fabricated on crystalline silicon wafers are shown to provide significant absorption enhancements. Through a combination of optical measurement and simulation, it is shown that the crossed grating provides better absorption enhancement than the linear grating, and that the parasitic reflector absorption is reduced by planarizing the rear reflector, leading to an increase in the useful absorption in the silicon. Finally, electrooptical simulations are performed of solar cells employing the fabricated grating structures to estimate efficiency enhancement potential.

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“…Absorption is expected to be higher if the grating structure is transferred to the Al. 36,37 Other approaches with Bragg reflectors have also been proposed to avoid parasitic absorption. 12,13 We find that a separation of the grating and rear reflector is necessary, not only for Al, but also for a less absorbing Ag reflector.…”

Section: B Implementation In Solar Cellsmentioning

confidence: 99%

“…Improper surface passivation has been shown to be a barrier for the successful implementation of back-side diffractive structures in solar cells. 36 The oxide layer used in this model may serve as a back-side passivation layer. In principle, a thin planar optically inactive oxide layer may be inserted between the grating layer and the bulk Si to further reduce surface recombination.…”

Section: B Implementation In Solar Cellsmentioning

confidence: 99%

Comparison of periodic light-trapping structures in thin crystalline silicon solar cells

Gjessing

Sudbø

Marstein

2011

Journal of Applied Physics

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Material costs may be reduced and electrical properties improved by utilizing thinner solar cells. Light trapping makes it possible to reduce wafer thickness without compromising optical absorption in a silicon solar cell. In this work we present a comprehensive comparison of the light-trapping properties of various bi-periodic structures with a square lattice. The geometries that we have investigated are cylinders, cones, inverted pyramids, dimples (half-spheres), and three more advanced structures, which we have called the roof mosaic, rose, and zigzag structure. Through simulations performed with a 20 μm thick Si cell, we have optimized the geometry of each structure for light trapping, investigated the performance at oblique angles of incidence, and computed efficiencies for the different diffraction orders for the optimized structures. We find that the lattice periods that give optimal light trapping are comparable for all structures, but that the light-trapping ability varies considerably between the structures. A far-field analysis reveals that the superior light-trapping structures exhibit a lower symmetry in their diffraction patterns. The best result is obtained for the zigzag structure with a simulated photo-generated current Jph of 37.3 mA/cm2, a light-trapping efficiency comparable to that of Lambertian light-trapping.

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Realization and evaluation of diffractive systems on the back side of silicon solar cells

Cited by 13 publications

References 0 publications

A numerical study of Bi-periodic binary diffraction gratings for solar cell applications

A numerical study of Bi-periodic binary diffraction gratings for solar cell applications

Nanoimprinted diffraction gratings for crystalline silicon solar cells: implementation, characterization and simulation

Comparison of periodic light-trapping structures in thin crystalline silicon solar cells

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