| 1. |
- Cunha, Jose M. V., et al.
(författare)
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High-Performance and Industrially Viable Nanostructured SiOx Layers for Interface Passivation in Thin Film Solar Cells
- 2021
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Ingår i: Solar RRL. - : John Wiley & Sons. - 2367-198X. ; 5:3
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Tidskriftsartikel (refereegranskat)abstract
- Herein, it is demonstrated, by using industrial techniques, that a passivation layer with nanocontacts based on silicon oxide (SiOx) leads to significant improvements in the optoelectronical performance of ultrathin Cu(In,Ga)Se-2 (CIGS) solar cells. Two approaches are applied for contact patterning of the passivation layer: point contacts and line contacts. For two CIGS growth conditions, 550 and 500 degrees C, the SiOx passivation layer demonstrates positive passivation properties, which are supported by electrical simulations. Such positive effects lead to an increase in the light to power conversion efficiency value of 2.6% (absolute value) for passivated devices compared with a nonpassivated reference device. Strikingly, both passivation architectures present similar efficiency values. However, there is a trade-off between passivation effect and charge extraction, as demonstrated by the trade-off between open-circuit voltage (V-oc) and short-circuit current density (J(sc)) compared with fill factor (FF). For the first time, a fully industrial upscalable process combining SiOx as rear passivation layer deposited by chemical vapor deposition, with photolithography for line contacts, yields promising results toward high-performance and low-cost ultrathin CIGS solar cells with champion devices reaching efficiency values of 12%, demonstrating the potential of SiOx as a passivation material for energy conversion devices.
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| 2. |
- Edoff, Marika, 1965-, et al.
(författare)
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Ultrathin CIGS Solar Cells with Passivated and Highly Reflective Back Contacts – : Results from the ARCIGS-M Consortium
- 2019
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Ingår i: Proceedings of 36th European Photovoltaic Solar Energy Conference and Exhibition. ; , s. 597-600
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this work, we report results from the EU-funded project ARCIGS-M. The project started in 2016 and aims to reduce the use of indium and gallium by enabling the use of very thin Cu(In,Ga)Se2 (CIGS) layers while retaining high efficiency and developing innovative low-cost steel substrates as alternatives to glass. In the project, reflective layers containing TCO´s and silver have successfully been used to enhance the reflective properties of the rear contact. In addition, passivation layers based on alumina (Al2O3) deposited by atomic layer deposition (ALD) have been found to yield good passivation of the rear contact. Since the alumina layers are dielectric, perforation of these layers is necessary to provide adequate contacting. The design of the perforation patterns has been investigated by a combination of modeling and experimental verification by electron beam lithography. In parallel a nano-imprint lithography (NIL) process is further developed for scale-up and application in prototype modules. Advanced optoelectrical characterization supported by modeling is used to fill in the missing gaps in optical and electrical properties, regarding CIGS, interfaces and back contact materials.
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| 3. |
- Kovacic, Milan, et al.
(författare)
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Light Management in Ultra-Thin Cu(In, Ga)Se2 Photovoltaic Devices
- 2019
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Ingår i: Proceedings of 36th European Photovoltaic Solar Energy Conference and Exhibition. - 3936338604 ; , s. 654-660
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Cu(In, Ga)Se2 (CIGS) solar cells exhibit high conversion efficiencies, with a recent record of 23.35 % on the cell level. However, an absorber thickness >1.8 m is required for efficient absorption of long-wavelength light. In order to minimize the material consumption (In, Ga and other elements) and to accelerate the fabrication process, further thinning down of CIGS absorber layer is important. One of the main challenges of ultra-thin absorber devices is to increase light absorption and consequently the photocurrent. We employ advanced optical simulations of ultra-thin (500 nm) CIGS devices in a PV module configuration, thus solar cell structure including encapsulation and front glass. Using simulations, we design and investigate different solutions for increased short circuit current, in particular (i) highly reflective back reflectors (BR), (ii) internal nano-textures and (iii) external textures by applying a light management foil. We show that any single solution (i, ii, iii) is not enough to compensate for the lower photocurrent, when thinning down (1800 nm -> 500 nm) the absorber layer. A combination of properly optimized internal or external textures and highly reflective back reflector is needed to reach, or even exceed (by ~3-5 %), the short circuit current of a standard thick (1800 nm) CIGS module structure.
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| 4. |
- Lontchi, Jackson, et al.
(författare)
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Optimization of Back Contact Grid Size in Al2O3-Rear-Passivated Ultrathin CIGS PV Cells by 2-D Simulations
- 2020
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Ingår i: IEEE Journal of Photovoltaics. - 2156-3381 .- 2156-3403. ; 10:6, s. 1908-1917
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Tidskriftsartikel (refereegranskat)abstract
- We present a simulation strategy using ATLAS-2D to optimize the back-contact hole grid (i.e., size and pitch of openings) of the Al 2 O 3 -rear-passivation layer in ultrathin Cu(In,Ga)Se 2 photovoltaic cells. We first discuss and compare our simulation model with a series of experimental nonpassivated and passivated cells to decouple the crucial passivation parameters. The simulation results follow the experimental trends, highlighting the beneficial effects of the passivation on the cell performances. Furthermore, it stresses the influence of the passivation quality at the Al 2 O 3 /Cu(In,Ga)Se 2 (CIGS) interface and of the contact resistance at the Mo/CIGS interface within the openings. Further simulations quantify significant improvements in short-circuit current and open-circuit voltage for different sizes of openings in the Al 2 O 3 layer, relative to an excellent passivation quality (i.e., high density of negative charges in the passivation layer). However, a degradation is predicted for a poor passivation (i.e., low density of such charges) or a high contact resistance. Consequently, we point out an optimum in efficiency when varying the opening widths at fixed hole-pitch and fixed contact resistance. At equivalent contact resistance, simulations predict that the sizes of the pitch and openings can be increased without optimal performance losses when maintaining a width to pitch ratio around 0.2. This simulation trends have been confirmed by a series of experiments, indicating that it is crucial to care about the dimensions of the opening grid and the contact resistance of passivated cells. These simulation results provide significant insights for optimal cell design and characterizations of passivated UT-CIGS PV cells.
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| 5. |
- Lontchi, Jackson, et al.
(författare)
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Ultra-thin CIGS : 2D Modelling and impactful results for optimal cell design and characterizations
- 2020
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Ingår i: 2020 47th IEEE Photovoltaic Specialists Conference (PVSC). - 9781728161150 - 9781728161167 ; , s. 699-700
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Konferensbidrag (refereegranskat)abstract
- We present a 2D model of an Al 2 O 3 -passivated ultrathin Cu(In, Ga)Se 2 photovoltaic cell with rear-contact pattern. Simulation results follow the experimental trends, highlighting the significant effects of the passivation quality and of the Mo/CIGS contact resistance. Improvements in Jsc and Voc are discussed for different sizes of openings, relative to an excellent passivation quality (i.e. high density of negative charges in the passivation layer). However, a degradation is predicted for a poor passivation (i.e. low density of such charges) or a high contact resistance. We point out an optimum in efficiency when varying the opening widths at fixed hole-pitch and fixed contact resistance for a width to pitch ratio around 0.2. These simulation results provide significant insights for optimal cell design and characterizations of passivated UT-CIGS PV cells.
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| 6. |
- Oliveira, Kevin, et al.
(författare)
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SiO$_x$ Patterned Based Substrates Implemented in Cu(In,Ga)Se$_2$ Ultrathin Solar Cells : Optimum Thickness
- 2022
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Ingår i: IEEE Journal of Photovoltaics. - : Institute of Electrical and Electronics Engineers (IEEE). - 2156-3381 .- 2156-3403. ; 12:4, s. 954-961
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Tidskriftsartikel (refereegranskat)abstract
- Interface recombination in sub-mu m optoelectronics has a major detrimental impact on devices' performance, showing the need for tailored passivation strategies to reach a technological boost. In this article, SiO$_x$ passivation based substrates were developed and integrated into ultrathin Cu(In,Ga)Se$_2$ (CIGS) solar cells. This article aims to understand the impact of a passivation strategy, which uses several SiO$_x$ layer thicknesses (3, 8, and 25 nm) integrated into high-performance substrates (HPS). The experimental study is complemented with 3-D lumerical finite-difference time-domain and 2-D Silvaco ATLAS optical and electrical simulations, respectively, to perform a decoupling of optical and electronic gains, allowing for a deep discussion on the impact of the SiO$_x$ layer thickness in the CIGS solar cell performance. This article shows that as the passivation layer thickness increases, a rise in parasitic losses is observed. Hence, a balance between beneficial passivation and optical effects with harmful architectural constraints defines a threshold thickness to attain the best solar cell performance. Analyzing their electrical parameters, the 8-nm novel SiO$_x$ based substrate achieved a light to power conversion efficiency value of 13.2%, a 1.3% absolute improvement over the conventional Mo substrate (without SiO$_x$).
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| 7. |
- Oliveira, Kevin, et al.
(författare)
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SiOx patterned based substrates implemented in Cu(In,Ga)Se-2 ultrathin solar cells : optimum thickness
- 2021
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Ingår i: 2021 IEEE 48th Photovoltaic Specialists Conference (PVSC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781665419222 ; , s. 928-930
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Konferensbidrag (refereegranskat)abstract
- Interface recombination in sub-mu m optoelectronic devices has a major harmful impact in devices performance, showing the need for tailored passivation strategies in order to reach a technological boost. In this work, SiOx based substrates were developed and integrated in ultrathin CIGS solar cells. This study aims at understanding the impact of several SiOx layer thicknesses (3, 8 and 25 nm) when this material is used as a passivation layer. Analysing their electrical parameters, the 8 nm novel SiOx based substrates achieved light to power conversion efficiency values up to 13.2 %, a 1.3 % absolute improvement over the conventional substrate (without SiOx).
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