| 1. |
- Keller, Jan, et al.
(författare)
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Wide-gap (Ag,Cu)(In,Ga)Se2 solar cells with different buffer materials—A path to a better heterojunction
- 2020
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Ingår i: Progress in Photovoltaics. - : Wiley. - 1062-7995 .- 1099-159X. ; 28:4, s. 237-250
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Tidskriftsartikel (refereegranskat)abstract
- This contribution concerns the effect of the Ag content in wide-gap AgwCu1-wIn1-xGaxSe2 (ACIGS) absorber films and its impact on solar cell performance. First-principles calculations are conducted, predicting trends in absorber band gap energy (Eg) and band structure across the entire compositional range (w and x). It is revealed that a detrimental negative conduction band offset (CBO) with a CdS buffer can be avoided for all possible absorber band gap values (Eg = 1.0–1.8 eV) by adjusting the Ag alloying level. This opens a new path to reduce interface recombination in wide-gap chalcopyrite solar cells. Indeed, corresponding samples show a clear increase in open-circuit voltage (VOC) if a positive CBO is created by sufficient Ag addition. A further extension of the beneficial compositional range (positive CBO at buffer/ACIGS interface) is possible when exchanging CdS with Zn1-ySnyOz, because of its lower electron affinity (χ). Nevertheless, the experimental results strongly suggest that at present, residual interface recombination still limits the performance of solar cells with optimized CBO, which show an efficiency of up to 15.1% for an absorber band gap of Eg = 1.45 eV.
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| 2. |
- Bayrak Pehlivan, Ilknur, et al.
(författare)
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Scalable and thermally-integrated solar water-splitting modules using Ag-doped Cu(In,Ga)Se2 and NiFe layered double hydroxide nanocatalysts
- 2022
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 10:22, s. 12079-12091
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Tidskriftsartikel (refereegranskat)abstract
- Photovoltaic (PV) electrolysis is an important and powerful technology for environmentally-friendly fuel production based on solar energy. By directly coupling solar cell materials to electrochemical systems to perform water electrolysis, solar energy can be converted into hydrogen fuel utilizing locally-generated heat and avoid losses from DC-DC convertors and power grid transmission. Although there have been significant contributions to the photoelectrochemical and PV-electrolysis field using isolated laboratory cells, the capacity to upscale and retain high levels of efficiency in larger modules remains a critical issue for widespread use and application. In this study, we develop thermally-integrated, solar-driven water-splitting device modules using AgCu(In,Ga)Se2 (ACIGS) and an alkaline electrolyzer system with NiFe-layered double hydroxide (LDH) nanocatalysts with devices of 82-100 cm2 area. The Ga-content in the ACIGS solar cells is tuned to achieve an optimal voltage for the catalyst system, and the average efficiencies and durability of the PV-electrolyzer were tested in up to seven-day indoor and 21 day outdoor operations. We achieved a solar-to-hydrogen (STH) module efficiency of 13.4% from gas volume measurements for the system with a six-cell CIGS-electrolyzer module with an active area of 82.3 cm2 and a 17.27% PV module efficiency under 100 mW cm−2 illumination, and thus 77% electricity-to-hydrogen efficiency at one full sun. Outdoor tests under mid-Europeen winter conditions exhibited an STH efficiency between 10 and 11% after the initial activation at the installation site in Jülich, Germany, in December 2020, despite challenging outdoor-test weather conditions, including sub-zero temperatures.
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| 3. |
- Bayrak Pehlivan, Ilknur, et al.
(författare)
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The climatic response of thermally integrated photovoltaic-electrolysis water splitting using Si and CIGS combined with acidic and alkaline electrolysis
- 2020
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Ingår i: Sustainable Energy & Fuels. - : ROYAL SOC CHEMISTRY. - 2398-4902. ; 4:12, s. 6011-6022
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Tidskriftsartikel (refereegranskat)abstract
- The Horizon 2020 project PECSYS aims to build a large area demonstrator for hydrogen production from solar energy via integrated photovoltaic (PV) and electrolysis systems of different types. In this study, Si- and CIGS-based photovoltaics are developed together with three different electrolyzer systems for use in the corresponding integrated devices. The systems are experimentally evaluated and a general model is developed to investigate the hydrogen yield under real climatic conditions for various thin film and silicon PV technologies and electrolyser combinations. PV characteristics using a Si heterojunction (SHJ), thin film CuInxGa1-xSe2, crystalline Si with passivated emitter rear totally diffused and thin film Si are used together with temperature dependent catalyst load curves from both acidic and alkaline approaches. Electrolysis data were collected from (i) a Pt-IrO2-based acidic electrolysis system, and (ii) NiMoW-NiO-based and (iii) Pt-Ni foam-based alkaline electrolysis systems. The calculations were performed for mid-European climate data from Julich, Germany, which will be the installation site. The best systems show an electricity-to-hydrogen conversion efficiency of 74% and over 12% solar-to-hydrogen (STH) efficiencies using both acidic and alkaline approaches and are validated with a smaller lab scale prototype. The results show that the lower power delivered by all the PV technologies under low irradiation is balanced by the lower demand for overpotentials for all the electrolysis approaches at these currents, with more or less retained STH efficiency over the full year if the catalyst area is the same as the PV area for the alkaline approach. The total yield of hydrogen, however, follows the irradiance, where a yearly hydrogen production of over 35 kg can be achieved for a 10 m(2) integrated PV-electrolysis system for several of the PV and electrolyser combinations that also allow a significant (100-fold) reduction in necessary electrolyser area for the acidic approach. Measuring the catalyst systems under intermittent and ramping conditions with different temperatures, a 5% lowering of the yearly hydrogen yield is extracted for some of the catalyst systems while the Pt-Ni foam-based alkaline system showed unaffected or even slightly increased yearly yield under the same conditions.
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| 4. |
- Rivalta, F., et al.
(författare)
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Effect of scanning strategy in the l‐pbf process of 18ni300 maraging steel
- 2021
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Ingår i: Metals. - : MDPI. - 2075-4701. ; 11:5
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Tidskriftsartikel (refereegranskat)abstract
- Maraging steels are good candidates for the laser powder bed fusion process (L‐PBF), also known as Selective Laser Melting, due to excellent weldability and resistance to quench cracking. Powders physical and chemical characteristics dominate the final microstructure and properties of the printed parts, that are also heavily influenced by the process parameters. In this study, the effects of the scanning strategies on dimensions, average surface roughness, density and material hardness were evaluated, keeping the powder type and the volumetric energy density (Andrew number) constant. The effects of the scanning strategy on these properties are far less understood than on other important ones, like residual stresses and distortion, strongly affected by the scanning strategy. In this study, parallel stripes, chessboard and hexagonal pattern strategies were studied, keeping the Andrew number constant but varying the interlayer rotation. In general, the hexagonal strategy underperformed compared to the chessboard and the stripes ones.
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