1,720,982 research outputs found
Computational screening of chalcogenides for intermediate band solar cells surpassing the Shockley–Queisser limit
Full text linkIntermediate band solar cells offer a promising avenue to surpass the Shockley-Queisser limit of ∼ 30 % that constrains conventional single-junction devices, with the potential to approach an efficiency limit of ∼ 45 % in terrestrial environments by incorporating a metallic band within the valence-conduction gap. Yet, their practical realization is challenged by difficulties in developing suitable intermediate band (IB) materials. Current approaches, which involve adding inclusions or utilizing highly mismatched alloys, often degrade material quality or present significant technological hurdles. A possible solution that remains underexplored, is to identify crystalline materials that inherently possess an IB and fine-tune their properties. In this work, thousands of crystalline chalcogenides are analyzed using a detailed balance model to quantitatively evaluate their expected efficacy as IB materials. Notably, orthorhombic VB 1 VIA 2 and IA 4 VIA 6 compounds, such as Ta 1 Se 2 and Cs 4 S 6 , are projected to achieve maximum efficiencies exceeding 35%, that is, surpassing the Shockley-Queisser limit. The interplay of IB filling and chemical substitution on the properties of these systems is analyzed, to unravel the impact on performance. This study not only identifies new material candidates for IB solar cells, but also provides insights into efficiency-property relations, hence advancing the understanding of these systems
Cement-Based Radiative Coolers for Photovoltaics: Towards a Practical Design
No full textResearch conducted in the framework of MIRACLE Project (Photonic Metaconcrete with Infrared RAdiative Cooling capacity for Large Energy savings, GA 964450), coordinated by Dr. Jorge Sánchez Dolado, from Centro de Física de Materiales (CFM).In 2014, the experimental realization of radiative coolers capable of reaching sub-ambient temperatures
under direct sunlight has opened up new possibilities for the thermal management of solar cells. Radiative
coolers eject excess heat by emitting thermal radiation within the so-called atmosphere transparency
window. The completely passive nature of this process and its reliance on material properties only, make
radiative coolers extremely attractive in terms of energy efficiency. Integrated with a photovoltaic cell, the
radiative cooler can reduce the cell operating temperature, leading to high efficiency and lifetime gains.
Yet, most radiative coolers in the literature are metamaterials with scarce elements or complex fabrications
processes, or organic materials with potential UV instability, with questionable economic viability or
reliability. To address this problem, we have recently proposed cement-based materials as a low-cost,
scalable and stable solution for photovoltaics cooling, showing that their electromagnetic properties can be
tuned to maximize their thermal emissivity by acting on their microstructure. In particular, using a detailed
balance model, we have demonstrated that their cooling performance could increase the efficiency of silicon
solar cells by up to 9% and extended their lifetime by up to 4 times. In this work, we take a further step
towards the experimental realization of this attractive concept, by investigating possible approaches,
requirements and prospects for the practical design of photovoltaic systems employing cement-based
radiative coolers.This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 964450.-- Conference Proceedings of the 16th ICCC, Bangkok, 18-22 September 2023.Peer reviewe
Interplay between chemical bonding, band structure and charge transport in thermoelectric chalcogenides
No full textThermoelectric power generators could aid reducing the carbon footprint of mankind by converting waste heat into electricity. Extensive research is being conducted to identify materials with suitable thermoelectric figures of merit. Yet, the values required have been elusive so far. The best thermoelectric performances to-date have been found in crystalline group IV chalcogenides, whose outstanding properties have been attributed to complex band structures and intrinsically low lattice thermal conductivities. The present dissertation aims at establishing a novel approach to identify chalcogenides suitable for thermoelectric applications. The work starts by inferring a correlation between metavalent bonding, octahedral coordination and high thermoelectric performance in crystalline p3 chalcogenides. A link between the three properties is proven by investigating charge transport in crystalline GeSe¬xTe1-x and GexSn1-xTe alloys. The strong anisotropy of the effective mass tensor of the relevant charge carriers is found to be the underlying mechanism. Other aspects of charge transport are also studied. Afterwards, a tight-binding model is defined for the band structure of crystalline group IV chalcogenides with metavalent bonding and octahedral coordination, which relates band gap and effective mass tensor to intuitive chemical coordinates. The model can explain the experimental findings and enables the definition of simple design rules for thermoelectric chalcogenides. Additionally, it is combined with the k⋅p method to determine tight-binding parameters (bond energies) and estimate the band structures of the samples under study from the experimental data. The work provides a better understanding of thermoelectric chalcogenides and is expected to accelerate the discovery of new materials for thermoelectric applications
Detailed-balance assessment of radiative cooling for multi-junction solar cells under unconcentrated and low-concentrated light
Full text linkMulti-junction solar cells are the best technology to achieve high-efficiency photovoltaics. Yet, their thermal management is crucial to ensure high performance and reliability, particularly in concentrating photovoltaic systems. Recent studies have proposed radiative cooling as an innovative, passive, cost-effective, and scalable technique to cool down solar cells. In this study, we analyze its impact on multi-junction solar cells under different illumination conditions by means of a detailed-balance model. First, we demonstrate that radiative cooling can provide greater efficiency gain in multi-junction devices than in single-junction ones despite the fact that the former heat up less than the latter. In fact, in multi-junction cells, the lower heating is more than compensated for by the stronger efficiency degradation with increasing temperature, due to their wider radiative recombination spectrum. Then, we explore two possible strategies to effectively use radiative cooling in low-concentration photovoltaic systems, such as building integrated concentrating photovoltaics. The first one is to combine the radiative cooler with a nonradiative cooling system, which then has relaxed performance requirements. The second one is to increase the radiative cooler area relative to that of the solar cell. Both approaches can provide significant performance benefits, whose magnitude depends on the selected design and application. For an optimal triple-junction cell under 10-sun concentration, we find that a radiative cooler having 5 the area of the solar cell reduces by 90% the nonradiative cooling power required to maintain the cell temperature at 60 C and achieves +2% absolute efficiency gain over 1-sun operation
Impact of Radiative Cooling on Multi-Junction Solar Cells Under Unconcentrated and Low-Concentrated Light
Full text linkMulti-junction solar cells are a key technology for high efficiency photovoltaics. Since their performance and reliability are strongly influenced by the operating temperature, their effective thermal management is an important concern, especially in concentrating photovoltaics. Radiative cooling is a cost-effective, passive, and scalable solution for thermal management of solar cells. This technique can effectively expel a large amount of heat by radiating it into outer space through the atmospheric transparency window between 8 and 13 μm, In this work, we analyze the impact of this cooling strategy on multi-junction solar cells under different illumination conditions by means of a detailed balance model for the cell/cooler system. We show that the increase in efficiency resulting from reduced operating temperature is more significant for multi-junction architectures in comparison to single-junction ones, because of their more negative temperature coefficient. Furthermore, we explore two viable approaches for successfully utilizing the radiative cooler in low-concentration photovoltaic systems. The first method involves increasing the size of the radiative cooler area, while the second entails combining it with a nonradiative cooling system
Detailed balance model of multi-junction solar cells with radiative cooling - dataset and code
No full textData, MATLAB software and plot scripts associated with the article "Detailed-balance assessment of radiative cooling for multi-junction solar cells under unconcentrated and low-concentrated light" (to appear in Solar Energy Materials and Solar Cells, 2024)
Impact of radiative cooling on the thermal behavior of multi-junction solar cells
Full text linkThermal radiation is a key aspect of solar cell thermal management. In this work we study, through detailed balance and
multiphysics simulations, the thermal behavior of multi-junction solar cells and the impact of different radiative cooling
designs on their achievable efficiency. We discuss the influence of the mid-infrared emissivity of the semiconductors
constituting the cell and possible encapsulating materials, with the goal of evaluating the performance improvements
achievable with an ideal thermal emitte
Thermoelectric Performance of IV-VI Compounds with Octahedral-Like Coordination: A Chemical-Bonding Perspective
No full textThermoelectric materials provide a challenge for materials design, since they require optimization of apparently conflicting properties. The resulting complexity has favored trial‐and‐error approaches over the development of simple and predictive design rules. In this work, the thermoelectric performance of IV–VI chalcogenides on the tie line between GeSe and GeTe is investigated. From a combination of optical reflectivity and electrical transport measurements, it is experimentally proved that the outstanding performance of IV–VI compounds with octahedral‐like coordination is due to the anisotropy of the effective mass tensor of the relevant charge carriers. Such an anisotropy enables the simultaneous realization of high Seebeck coefficients, due to a large density‐of‐states effective mass, and high electrical conductivity, caused by a small conductivity effective mass. This behavior is associated to a unique bonding mechanism by means of a tight‐binding model, which relates band structure and bond energies; tuning the latter enables tailoring of the effective mass tensor. The model thus provides atomistic design rules for thermoelectric chalcogenides
Cementitious materials as promising radiative coolers for solar cells
Full text linkPart of special issue: SI: Advanced thermal control: fundamentals and applications. Edited by Miguel Muñoz Rojo, Andrej Kitanovski, Karl Joulain.Research conducted in the framework of MIRACLE Project (Photonic Metaconcrete with Infrared RAdiative Cooling capacity for Large Energy savings, GA 964450), coordinated by Dr. Jorge Sánchez Dolado, from Centro de Física de Materiales (CFM).Nowadays, radiative coolers are extensively investigated for the thermal management of solar cells with the aim of improving their performance and lifetime. Current solutions rely on meta-materials with scarce elements or complex fabrication processes, or organic polymers possibly affected by UV degradation. Here, the potential of innovative cement-based solutions as a more sustainable and cost-effective alternative is reported. By combining chemical kinetics, molecular mechanics and electromagnetic simulations, it is shown that the most common cements, i.e., Portland cements, can be equipped with excellent radiative cooling properties, which might enable a reduction of the operating temperature of solar cells by up to 20 K, with outstanding efficiency and lifetime gains. This study represents a first step toward the realization of a novel class of energy-efficient, economically viable and robust radiative coolers, based on cheap and available cementitious materials.This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No. 964450.Peer reviewe
Temperature of single-junction solar cells with Ordinary Portland Cement radiative cooler
No full textResearch conducted in the framework of MIRACLE Project (Photonic Metaconcrete with Infrared RAdiative Cooling capacity for Large Energy savings, GA 964450), coordinated by Dr. Jorge Sánchez Dolado, from Centro de Física de Materiales (CFM).[The OPC emissivity has been calculated with Transfer-Matrix-Method applied to a slab having roughness RMS and complex permittivity obtained by applying the effective medium theory of Slovick (Slovick, B. A. Negative Refractive Index Induced by Percolation in Disordered Metamaterials. Physical Review B 95, 094202 (2017)) to the OPC microstructure calculated with µic (https://micepfl.sourceforge.net/) and using the complex permittivity obtained by CSIC with GULP (https://gulp.curtin.edu.au/) for the homogeneous phases. This is described in detail in Cagnoni, M., Tibaldi, A., Dolado, J. S. & Cappelluti, F. Cementitious Materials as Promising Radiative Coolers for Solar Cells. iScience 25, 105320 (2022).][The solar cell operating temperature when coupled to the OPC based radiative cooler has been obtained by means of the detailed-balance model commonly employed in the literature. This is discussed in detail in Cagnoni, M., Tibaldi, A., Dolado, J. S. & Cappelluti, F. Cementitious Materials as Promising Radiative Coolers for Solar Cells. iScience 25, 105320 (2022).]This dataset contains information of the behavior of temperature of single-junction solar cells with Ordinary Portland Cement radiative cooler.- The OPC emissivity has been calculated with Transfer-Matrix-Method applied to a slab having roughness RMS and complex permittivity obtained by applying the effective medium theory of Slovick (Slovick, B. A. Negative Refractive Index Induced by Percolation in Disordered Metamaterials. Physical Review B 95, 094202 (2017)) to the OPC microstructure calculated with µic (https://micepfl.sourceforge.net/) and using the complex permittivity obtained by CSIC with GULP (https://gulp.curtin.edu.au/) for the homogeneous phases. This is described in detail in Cagnoni, M., Tibaldi, A., Dolado, J. S. & Cappelluti, F. Cementitious Materials as Promising Radiative Coolers for Solar Cells. iScience 25, 105320 (2022). - The solar cell operating temperature when coupled to the OPC based radiative cooler has been obtained by means of the detailed-balance model commonly employed in the literature. This is discussed in detail in Cagnoni, M., Tibaldi, A., Dolado, J. S. & Cappelluti, F. Cementitious Materials as Promising Radiative Coolers for Solar Cells. iScience 25, 105320 (2022).European Commission: 964450Peer reviewe
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