Light Trapping in Ultrathin CIGS Solar Cells with Nanostructured Back Mirrors

Goffard, Julie; Colin, Clément; Mollica, Fabien; Cattoni, Andréa; Sauvan, Christophe; Lalanne, Philippe; Guillemoles, Jean‐François; Naghavi, Negar; Collin, Stéphane

doi:10.1109/jphotov.2017.2726566

Cited by 58 publications

(31 citation statements)

References 34 publications

(40 reference statements)

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“…Simply, the chemical passivation allows for the decrease of the total number of electrically active defects. [38][39][40][41] Ultrathin devices have recently been studied in detail by numerous groups [42][43][44][45][46][47] as they have the potential to reduce the material costs and manufacturing times. Such field is beneficial for the electrical performance of the solar cell, since it drives minority carriers away from the highly recombinative rear contact into the space charge region.…”

Section: Introductionmentioning

confidence: 99%

“…[36,37] These findings have motivated device simulations that have predicted gains up to 3% (in absolute power conversion efficiency) in fully passivated solar cells. [38][39][40][41] Ultrathin devices have recently been studied in detail by numerous groups [42][43][44][45][46][47] as they have the potential to reduce the material costs and manufacturing times. [48] Ultrathin devices are believed to be the forward path in this CIGS technology as they enable a combination of significant advantages: (i) lower material consumption, which is of crucial industrial importance mainly due to In scarcity; (ii) increased mechanical flexibility and integration in a broad range of consumer-oriented applications (e.g., BIPV, portable electronics, wearables, internet of things, etc.…”

Section: Introductionmentioning

confidence: 99%

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Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer

Salomé

Vermang

Ribeiro‐Andrade

et al. 2017

Adv Materials Inter

110

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Thin film solar cells based in Cu(In,Ga)Se2 (CIGS) are among the most efficient polycrystalline solar cells, surpassing CdTe and even polycrystalline silicon solar cells. For further developments, the CIGS technology has to start incorporating different solar cell architectures and strategies that allow for very low interface recombination. In this work, ultrathin 350 nm CIGS solar cells with a rear interface passivation strategy are studied and characterized. The rear passivation is achieved using an Al2O3 nanopatterned point structure. Using the cell results, photoluminescence measurements, and detailed optical simulations based on the experimental results, it is shown that by including the nanopatterned point contact structure, the interface defect concentration lowers, which ultimately leads to an increase of solar cell electrical performance mostly by increase of the open circuit voltage. Gains to the short circuit current are distributed between an increased rear optical reflection and also due to electrical effects. The approach of mixing several techniques allows us to make a discussion considering the different passivation gains, which has not been done in detail in previous works. A solar cell with a nanopatterned rear contact and a 350 nm thick CIGS absorber provides an average power conversion efficiency close to 10%.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer

Salomé

Vermang

Ribeiro‐Andrade

et al. 2017

Adv Materials Inter

110

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show abstract

“…Electron-hole pairs are produced at the rate G(z) defined in Eq. (7) and recombine at the rate R(n, p; z). We incorporated the radiative recombination and SRH recombination processes via R(n, p; z) = R rad (n, p; z)+ R SRH (n, p; z) [23,18].…”

Section: Electrical Theorymentioning

confidence: 99%

Efficiency enhancement of ultrathin CIGS solar cells by optimal bandgap grading

et al. 2019

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The power conversion efficiency of an ultrathin CuIn 1−ξ Ga ξ Se2 (CIGS) solar cell was maximized using a coupled optoelectronic model to determine the optimal bandgap grading of the nonhomogeneous CIGS layer in the thickness direction. The bandgap of the CIGS layer was either sinusoidally or linearly graded, and the solar cell was modeled to have a metallic backreflector corrugated periodically along a fixed direction in the plane. The model predicts that specially tailored bandgap grading can significantly improve the efficiency, with much smaller improvements due to the periodic corrugations. An efficiency of 27.7% with the conventional 2200-nm-thick CIGS layer is predicted with sinusoidal bandgap grading, in comparison to 22% efficiency obtained experimentally with homogeneous bandgap. Furthermore, the inclusion of sinusoidal grading increases the predicted efficiency to 22.89% with just a 600-nm-thick CIGS layer. These high efficiencies arise due to a large electron-hole-pair generation rate in the narrow-bandgap regions and the elevation of the open-circuit voltage due to a wider bandgap in the region toward the front surface of the CIGS layer. Thus, bandgap nonhomogeneity, in conjunction with periodic corrugation of the backreflector, can be effective in realizing ultrathin CIGS solar cells that can help overcome the scarcity of indium.

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“…Apart from all the above‐mentioned fabrication complexities, the main drawback with these type of designs is the polarization sensitivity of the grating structure where it can support SPP modes in TM polarization not in TE one. The replacement of this 1D elongated grating with periodic patches, or fishnet‐like holes will reinforce the efficient operation of the structure in all light polarizations . This is important for the practical application of this strategy considering the fact that the incident solar irradiation is also unpolarized.…”

Section: Light Trapping Schemesmentioning

confidence: 99%

Semiconductor Thin Film Based Metasurfaces and Metamaterials for Photovoltaic and Photoelectrochemical Water Splitting Applications

Ghobadi

Özbay

2019

Advanced Optical Materials

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throughput and large-scale compatibility. The photoactive material is generally composed of single or multiple semiconductor layers responsible for harvesting solar energy. This harvested solar irradiation can be used to generate electricity using photovoltaic (PV) devices, or it can be converted to chemical energy in the form of hydrogen which is the case for photoelectrochemical water splitting (PEC-WS). In both PV and PEC-WS applications, the ultimate goal is to establish an efficient photon capturing and electron collecting scheme to generate a huge number of photocarriers (including electron-hole pairs) with rational carrier dynamics (efficient charge generation, separation, and collection). This means that the device should be optically thick enough to generate high carrier's density and electrically thin enough to collect photogenerated carrier before they recombine. When light impinges a semiconductor surface, a part of the light is reflected back due to the mismatch between the air and the semiconductor layer refractive index. The rest will propagate within the bulk until it is fully absorbed by the semiconductor slab. The optical penetration depth (LPD) is defined as the depth at which the incident power falls to 1/e (≈37%) of its input value. This parameter differs from one semiconductor to another and it depends on the extinction coefficient (κ) of the In both photovoltaic (PV) and photoelectrochemical water splitting (PEC-WS) solar conversion devices, the ultimate aim is to design highly efficient, low cost, and large-scale compatible cells. To achieve this goal, the main step is the efficient coupling of light into active layer. This can be obtained in bulkysemiconductor-based designs where the active layer thickness is larger than light penetration depth. However, most low-bandgap semiconductors have a carrier diffusion length much smaller than the light penetration depth. Thus, photogenerated electron-hole pairs will recombine within the semiconductor bulk. Therefore, an efficient design should fully harvest light in dimensions in the order of the carriers' diffusion length to maximize their collection probability. For this aim, in recent years, many studies based on metasurfaces and metamaterials were conducted to obtain broadband and near-unity light absorption in subwavelength ultrathin semiconductor thicknesses. This review summarizes these strategies in five main categories: light trapping based on i) strong interference in planar multilayer cavities, ii) metal nanounits, iii) dielectric units, iv) designed semiconductor units, and v) trapping scaffolds. The review highlights recent studies in which an ultrathin active layer has been coupled to the above-mentioned trapping schemes to maximize the cell optical performance.

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Light Trapping in Ultrathin CIGS Solar Cells with Nanostructured Back Mirrors

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Cited by 58 publications

References 34 publications

Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer

Passivation of Interfaces in Thin Film Solar Cells: Understanding the Effects of a Nanostructured Rear Point Contact Layer

Efficiency enhancement of ultrathin CIGS solar cells by optimal bandgap grading

Semiconductor Thin Film Based Metasurfaces and Metamaterials for Photovoltaic and Photoelectrochemical Water Splitting Applications

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