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

Bhattacharya, Sayak; John, Sajeev

doi:10.1103/physrevapplied.9.044009

Cited by 31 publications

(18 citation statements)

References 59 publications

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“…We realized two types of 10-μm thick simple-cubic PhC, the inverted pyramid PhC with lattice constant a = 2,500 nm and the Teepee PhC with a = 1,200 nm. Despite the fact that these structures are not fully optimized 19,20 for solar light trapping, we observe that both PhC structures exhibit solar absorption well beyond the Lambertian limit in the weakly absorbing near-infrared regime, λ = 950-1,200 nm. Furthermore, we found the maximum-achievable-photocurrent-density (MAPD) under AM1.5G illumination at 4-degree incident angle to be 41.29 and 41.52 mA/cm 2 for the inverted pyramid and the Teepee PhC, respectively.…”

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confidence: 78%

“…Both the Inverted Pyramid and Teepee PhCs were theoretically optimized 19 , 20 and the fabricated structures are not far from the optimal geometries. Figure 1 e,f shows a schematic design and SEM (scanning electron micrograph) image of the IP structure, respectively.…”

Section: Sample Design and Fabricationmentioning

confidence: 99%

“…While traditional 2D photonic crystals guide light in the 2D plane 16 , our new type of 2D photonic crystal deflects sunlight from the z-direction and couples it into the x-y plane 17,18 . In contrast to 165 μm-thick Kaneka cell and 110 μm-thick Lambertian cell, the PhC cells are 10-15 μm thick and have conversion efficiencies exceeding 30% 1,19,20 . The key mechanisms enabling the 30% cell using just 10-15 μm thick silicon are the existence of slow-light resonances and parallel-to-interface refraction (PIR) 21 .…”

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confidence: 99%

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Experimental demonstration of broadband solar absorption beyond the lambertian limit in certain thin silicon photonic crystals

Hsieh

Kaiser

Bhattacharya

et al. 2020

Sci Rep

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The tantalizing possibility of 31% solar-to-electric power conversion efficiency in thin film crystalline silicon solar cell architectures relies essentially on solar absorption well beyond the Lambertian light trapping limit (Bhattacharya and John in Nat Sci Rep 9:12482, 2019). Up to now, no solar cell architecture has exhibited above-Lambertian solar absorption, integrated over the broad solar spectrum. In this work, we experimentally demonstrate two types of photonic crystal (PhC) solar cells architectures that exceed Lambertian light absorption, integrated over the entire 300-1,200 nm wavelength band. These measurements confirm theoretically predicted wave-interference-based optical resonances associated with long lifetime, slow-light modes and parallel-to-interface refraction. These phenomena are beyond the realm of ray optics. Using two types of 10-μm thick PhC's, first an Inverted Pyramid PhC with lattice constant a = 2,500 nm and second a Teepee PhC with a = 1,200 nm, we observe solar absorption well beyond the Lambertian limit over λ = 950-1,200 nm. Our absorption measurements correspond to the maximum-achievable-photocurrent-density (MAPD), under AM1.5G illumination at 4-degree incident angle, 41.29 and 41.52 mA/cm 2 for the Inverted Pyramid and Teepee PhC, respectively, in agreement with wave-optics, numerical simulations. Both of these values exceed the MAPD (= 39.63 mA/cm 2) corresponding to the Lambertian limit for a 10-μm thick silicon for solar absorption over the 300-1,200 nm band. The efficiency and cost of photovoltaics has steadily improved in recent years in the effort to create a competitive renewable energy resource. Silicon solar cells have been the dominant driving force in photovoltaics due to the abundance and environmentally friendly nature of silicon. The maximum possible power conversion efficiency of a single junction, crystalline silicon (c-Si) solar cell under one sun illumination at room temperature is 32.33% 2. The highest efficiency real-world n-type silicon solar cell to date, by Kaneka Corp 3,4 , exhibits 26.7% conversion efficiency, followed closely by the p-type silicon solar cell, by the Institute for Solar Energy Research Hamelin (ISFH), Germany with 26.1% efficiency 5,6. An analysis of the Kaneka, 165 μm thick, c-Si cell shows that in the absence of any extrinsic loss mechanism, the limiting efficiency of such a cell is 29.1% 3. The competing factors responsible for this limit of the conversion efficiency are ray-optics light trapping 7,8 and intrinsic loss due to Auger charge-carrier recombination. Essentially, the thicker the cell, the more light is absorbed. However, this is accompanied by increased bulk non-radiative recombination loss of charge carriers. In the case of ideal Lambertian light-trapping and a state-of-the-art Auger recombination model 9 , the optimal silicon thickness is reduced to 110 μm and a theoretical limit to conversion efficiency (assuming no surface recombination losses) is increased to 29.43% 8. In traditional ray-optics based light trapping s...

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confidence: 78%

Section: Sample Design and Fabricationmentioning

confidence: 99%

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confidence: 99%

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Experimental demonstration of broadband solar absorption beyond the lambertian limit in certain thin silicon photonic crystals

Hsieh

Kaiser

Bhattacharya

et al. 2020

Sci Rep

Self Cite

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“…It is worth noting that due to reciprocity of light propagation (in the linear regime), PhC structures can also be used for light-trapping. It was shown, both theoretically [12] and experimentally [13], that by optimizing the dimensions of the PhC, very high absorption efficiencies can be achieved.…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional photonic crystals increasing vertical light emission from Si nanocrystal-rich thin layers

Ondič

Varga

Pelant

et al. 2018

Beilstein J. Nanotechnol.

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We have fabricated two-dimensional photonic crystals (PhCs) on the surface of Si nanocrystal-rich SiO2 layers with the goal to maximize the photoluminescence extraction efficiency in the normal direction. The fabricated periodic structures consist of columns ordered into square and hexagonal pattern with lattice constants computed such that the red photoluminescence of Si nanocrystals (SiNCs) could couple to leaky modes of the PhCs and could be efficiently extracted to surrounding air. Samples having different lattice constants and heights of columns were investigated in order to find the configuration with the best performance. Spectral overlap of the leaky modes with the luminescence spectrum of SiNCs was verified experimentally by measuring photonic band diagrams of the leaky modes employing angle-resolved spectroscopy and also theoretically by computing the reflectance spectra. The extraction enhancement within different spatial angles was evaluated by means of micro-photoluminescence spectroscopy. More than 18-fold extraction enhancement was achieved for light propagating in the normal direction and up to 22% increase in overall intensity was obtained at the spatial collection angle of 14°.

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“…A reduction in τ SRH to 1.2ms typically leads to a 0.5% loss in efficiency. We have also shown the robustness of our inverted micro-pyramid structure to variations in the photonic crystal lattice constant.X − Y symmetry breaking in photonic crystals has been found to be an effective way to further increase solar absorption in thin-film c−Si cells[60]. Symmetry-breaking of our square-lattice, inverted micro-pyramid PhC may likewise enable further improvement in MAPD over the 300 − 1200nm spectral range.…”

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Towards 30% Power Conversion Efficiency in Thin-Silicon Photonic-Crystal Solar Cells

et al. 2019

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By direct numerical solution of Maxwell's equations and the semiconductor drift-diffusion equations, we demonstrate solar power conversion efficiencies in the 29%−30% range in crystalline-silicon photonic-crystal solar cells. These 3 − 12 µm thick photonic crystals, consisting of wavelength-scale inverted-pyramid arrays, absorb sunlight considerably in excess of the Lambertian limit due to wave-interference based light-trapping. It is suggested that the resulting optimized balance between bulk-Auger recombination and solar absorption occurs for a silicon thickness of 10 µm, in contrast to previous estimates of over 100 µm. Optimized n + pp + doping profiles involving low p−doping throughout most of the bulk and thin n + and p + −doping at the emitter and base regions yield ideal electronic response. For solar absorption restricted to the 300 − 1100 nm range, we obtain a short circuit current of 42.5 mA/cm 2 , an open circuit voltage of nearly 0.8 V and a fill-factor of about 87%, provided that the surface recombination velocities are below 100 cm/s. Including solar absorption in the 1100 − 1200 nm range through electronic bandgap narrowing and the Urbach optical absorption edge, our wave-interference-based light-trapping enables an additional photo-current density of 1.09 mA/cm 2 for an overall power conversion efficiency of 30%. It is shown that under solar concentration by factors of 20 and 150, the power conversion efficiencies are enhanced to 32.5% and 33.5%, respectively.

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

Cited by 31 publications

References 59 publications

Experimental demonstration of broadband solar absorption beyond the lambertian limit in certain thin silicon photonic crystals

Experimental demonstration of broadband solar absorption beyond the lambertian limit in certain thin silicon photonic crystals

Two-dimensional photonic crystals increasing vertical light emission from Si nanocrystal-rich thin layers

Towards 30% Power Conversion Efficiency in Thin-Silicon Photonic-Crystal Solar Cells

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