Solution-Processed, Solid-State Solar Cells based on Environmentally Friendly AgBiS2 Nanocrystals

Solution-processed inorganic solar cells are a promising low-cost alternative to firstgeneration solar cells.1,2 Solution processing at low temperatures and the use of nontoxic and abundant elements can help minimize cost and facilitate regulatory acceptance. However, until now there has been no material that exhibits all of these features while demonstrating promising efficiencies. Many of the most promising solution-processed inorganic solar cells contain toxic elements such as lead or cadmium (perovskites,2,3 PbS,4 CdTe,5,6 CdS(Se)7,8) or scarce elements like tellurium or indium (CdTe, CIGS(Se)/CIS9,10). Others require high-temperature processes such as selenization or sintering or rely on vacuum deposition techniques ((Sb2S(Se)3,11–13 SnS,14,15 CZTS(Se)16). Here, we present AgBiS2 nanocrystals as a novel nontoxic,17 earth-abundant18 material for highperformance, solution-processed solar cells fabricated in ambient conditions at low temperatures (≤100°C). The AgBiS2 nanocrystals have favorable properties for solar-cell applications including a near-ideal bandgap and strong, broad absorption. We demonstrate a Newport certified power conversion efficiency of 6.3% with no hysteresis and a remarkably high short-circuit current density of about 22 mA·cm-2 for an active layer thickness of only ~35 nm.Peer ReviewedPostprint (author's final draft

Networks of action situations in point-source pollution : the case of winery wastewater in Aragon, Spain

Unidad de excelencia María de Maeztu CEX2019-000940-MIn this article, we offer an analysis of point-source water pollution governance in the European agri-food sector. Specifically, we tackle the case study of the wine industry in Aragon (Spain) through the lenses of the networks of action situations approach. We unveil key strategic decisions of wine producers in relation to compliance with water discharge regulations and explore the feasibility and effectiveness of potential solutions. According to our quantitative and qualitative analyses, the problem of peak load discharges in the sector can be explained by the strategic behavior of wine producers in the context of enforcement deficits, as well as by particularities of the wine production process, and controversies around the construction and management of public treatment plants. Coordination among wine producers and public treatment plant managers to invest in in-house treatment infrastructure or to smooth discharges out so they fit the capacity of treatment plants would be a promising solution; however, economic incentives and tightened enforcement of discharge regulations would also be necessary

High frequency response of adenine-derived carbon in aqueous electrochemical capacitor

Electrochemical capacitors are attractive power sources, especially when they are able to operate at high frequency (high current regime). In order to meet this requirement their constituents should be made of high conductivity materials with a suitable porosity. In this study, enhanced power and simultaneously high capacitance (120 F g−1 at 1 Hz or 10 A g−1) electrode material obtained from carbonized adenine precursor is presented. A micro/mesoporous character of the carbon with optimal pore size ratio and high surface area was proven by the physicochemical characterization. The beneficial pore structure and morphology resembling highly conductive carbon black, together with a significant nitrogen content (5.5%) allow for high frequency response of aqueous capacitor to be obtained. The carbon/carbon symmetric capacitor (in 1 mol L−1 Li2SO4) has been tested to the voltage of 1.5 V. The cyclic voltammetry indicates a good electrochemical response even at high scan rate (50 mV s−1). The cyclability of the capacitor is comparable to the one operating with commercial carbon (YP50F). The adenine-based capacitor is especially favourable for stationary applications requiring high power.Partners acknowledge M-ERA.NET network, MCIN/AEI/10.13039/501100011033 (Ref. PCI2019–103637), CIBER-BBN, ICTS ‘‘NANBIOSIS’’, ICTS ELECMI node "Laboratorio de Microscopias Avanzadas", National Science Centre, Poland (2018/30/Z/ST4/00901), and Ministrstvo za izobraževanje, znanost in šport for financial support and the grant of Ministry of Science and Higher Education in Poland, no. 0911/SBAD/2101. A.V., B.T., E.T. and R.D. additionally acknowledge financial support from the Slovenian Research Agency (ARRS) research core funding P2–0393.Peer reviewe

Renewable Energy Production

Coordinator: Hernán Míguez.Peer reviewe

Research Update: Bismuth based materials for photovoltaics

In this Research Update, we briefly summarize some of the bismuth materials that have been investigated for their use in photovoltaic solar cells. We focus on bismuth-based perovskites and bismuth halides, as alternatives to lead-halide perovskites, and bismuth-based sulfides (Bi2S3, CuxBiySz, and AgBiS2), as alternatives to lead sulfide quantum dots. These materials fulfill the requirements of being composed of abundant and non-toxic elements. Moreover, they exhibit adequate properties for photovoltaics like high absorption coefficients and suitable bandgaps, plus additional attractive characteristics in terms of robustness and stability. However, they have not been extensively studied and therefore their efficiencies are still far from those reported for their toxic counterparts. Here we collect some of the most promising results, point at possible limiting factors, and suggest some routes to improve performance

Earth-abundant non-toxic perovskite nanocrystals for solution processed solar cells

Semiconductor nanocrystals, used in quantum dot solar cells, are interesting materials for photovoltaics because they can be obtained in solution and can be composed of abundant elements. Moreover, as compared to other photovoltaic materials, nanomaterials show unique features due to their novel size- and shape-dependent properties such as band gap tuning, multiple exciton generation, and modulation of n- or p-type behaviour by doping or by modifying the ligands on the surface of the nanocrystals. Quantum dot solar cells, together with perovskite solar cells, are the latest incorporation to photovoltaic technologies and have already shown impressive progress in efficiencies and great promise as alternatives to commercial solar cells. However, in all cases, the highest efficiencies are obtained with materials that contain lead in their composition. To solve the problem of toxicity, several materials have been proposed as substitutes. In this review, we summarize some of the non-toxic alternatives that have been synthesized as nanocrystals and incorporated in photovoltaic solar cells, specifically: tin (Sn), germanium (Ge), bismuth (Bi), and antimony (Sb)-based materials. Our findings show that this field has been scarcely covered; there are very few reports on non-toxic perovskite nanocrystals incorporated in solar cells and in general, the efficiencies are still modest. However, this area deserves more attention since some nanocrystal-based solar cells already outperform bulk counterparts. For each case, we also discuss factors limiting efficiency, the approaches followed to overcome these limitations, and the possible solutions to improve efficiency.Authors acknowledge Fundación Iberdrola España, CIBER-BBN (financed by the Instituto de Salud Carlos III with assistance from the European Regional Development Fund), the ICTS “NANBIOSIS”, Agencia Estatal de Investigación-AEI (Ref. PID2019-107893RB-I00 and PID2019-104307GB-I00), and Gobierno de Aragón (Ref. T57_20R and E47_20R) for financial support.Peer reviewe

Photocatalytic rermoval of contaminants in water using nanostructured metal oxides

Resumen del póster presentado a la XXXVIII Reunión Bienal de la Real Sociedad Española de Química, celebrada en el Palacio de Congresos de Granada, del 27 de junio al 30 de junio de 2022.An important variety of metal oxides are photoactive semiconductor solids with the capacity to generate Reactive Oxygen Species (ROS) in aqueous media. The excellent oxidizing capacity of these ROS has been studied by the scientific community in the elimination of pollutants as part of the Advanced Oxidation Processes (AOPs) in the purification of polluted water. The main photocatalysts used to date (TiO2, ZnO, g-C3N4...) are only capable of being photoactivated with UV radiation, which means that they can only take advantage of a small fraction of the solar spectrum; or require the use of UV lamps, with the consequent energy consumption. For this reason, this work has proposed the development of new photocatalysts with narrower band gaps capable of generating ROS when irradiated with Visible-NIR photons, thus taking advantage of the largest possible portion of the sunlight spectrum. New nanostructured metal oxides based on Fe and W, photoactive with visible light, have been obtained. In addition, some hybrids consisting of photoactive substrates with semiconductor nanocrystals have been developed, thus improving the photocatalytic properties of the initial materials separately. Finally, all these materials have been tested and optimized in photocatalysis experiments in aqueous suspension of model pollutants.Peer reviewe

Dendrimer-encapsulated Pd nanoparticles versus palladium acetate as catalytic precursors in the stille reaction in water

The performance of several palladium precatalysts, namely, palladium(II) acetate, palladium(0) nanoparticles encapsulated into poly(amidoamine) (PAMAM) dendrimers (Pd DENs), and palladium(II)-PAMAM complexes, in the Stille reaction between trichloro(phenyl)stannane and iodoarenes in water is compared. The reactivity of Pd DENs is similar or inferior to that of palladium(II) acetate, although the presence of the dendrimer suppresses the formation of homocoupling products and allows catalyst recycling. It is suggested that the reaction catalyzed by Pd DENs occurs via palladium species which are leached from the nanoparticle but which remain coordinated to the dendritic macromolecule.We gratefully acknowledge financial support from the Spanish Ministerio de Educación y Ciencia (project CTQ2005-00795/BQU) and the Comunidad de Madrid (project S-0505/PPQ/0328-03 and a postdoctoral contract to M.B.)

Estudio de las capas de transporte de electrones en las celdas solares

En este Trabajo de Fin de Máster se ha llevado a cabo en un laboratorio una evaluación detallada de la capa transportadora de electrones, así como su influencia en dos tipos de celdas solares (perovskita de haluro híbrido (PVK) y AgBiS2), evaluando para ello la estabilidad y el rendimiento de los dispositivos. El objetivo de este proyecto era desarrollar celdas solares con una capa transportadora de electrones basada en SnO2, obtenido a partir de diferentes precursores y comprender su influencia utilizando diversas técnicas actuales de caracterización fisicoquímica. El propósito de desarrollar dicho trabajo radica en la mejora de estos dispositivos fotovoltaicos mediante la consecución de mayores rendimientos. El proyecto abarcó cuatro pasos principales: revisión bibliográfica, experimentación, análisis y discusión de los resultados, y principales conclusiones. Se estudió la bibliografía más relevante para conocer los fundamentos de las celdas solares de PVK y AgBiS2, los materiales y los principios de funcionamiento. El trabajo experimental combinó la síntesis, la caracterización química y estructural del SnO2 como capa transportadora de electrones, así como la fabricación de ambos tipos de celdas solares. Este estudio aporta la posibilidad de desarrollar nuevas estrategias de fabricación de alta calidad de capas transportadoras de electrones a bajas temperaturas, basadas en la deposición directa de nanopartículas, o utilizando diferentes precursores. <br /

Matildite versus schapbachite: First-principles investigation of the origin of photoactivity in AgBiS2

Recent experiments motivated by solar light harvesting applications have brought a renewed interest in AgBiS2 as an environmentally friendly material with appealing photovoltaic properties. The lack of detailed knowledge on its bulk structural and electronic structure however inhibits further development of this material. Here we have investigated by first-principles quantum mechanical methods models of the two most commonly reported AgBiS2 crystal structures, the room temperature matildite structure, and the metastable schapbachite. Density functional theory (DFT) based calculations using the Perdew-Burke-Ernzerhof exchange-correlation (xc) functional reveal that matildite can be 0.37 eV per AgBiS2 stoichiometry unit more stable than a schapbachite structure in bulk, and that the latter, in its ordered form, may display a metallic electronic structure, precluding its use for solar light harvesting. This points out the fact that AgBiS2 nanocrystals used in solar cells should present a structure based on matildite. Matildite is found to be an indirect gap semiconductor, with an estimated band gap of ∼1.5 eV according to DFT based calculations using the more accurate hybrid xc functionals. These reveal that hole effective mass is twice that of electron effective mass, with concomitant consequences for the generated exciton. Hybrid DFT calculations also show that matildite has a high dielectric constant pertinent to that of an ionic semiconductor and slightly higher than that of PbS, a material that has been extensively used in solar cells in its nanocrystalline form. The calculated Bohr exciton radius of 4.6 nm and the estimated absorption coefficient of 10E5 cm−1 within the solar light spectrum are well in line with those experimentally reported in the literature