Explorando la dinámica del Sn durante la síntesis de celdas de alta eficiencia basadas en Cu2ZnSnSe4

Treballs Finals de Grau d'Enginyeria de Materials, Facultat de Química, Universitat de Barcelona, Any: 2020, Tutors: Alejandro Pérez Rodriguez, Edgardo SaucedoThe need for new renewable sources of energy has been a reality for several years. Both because our current source of energy, fossil fuels, is limited, and because of the high pollution and problems associated with their use. As a solution to this problem, the development of renewable energies is our best asset. Within the wide range of possibilities, this work focuses on the energy that directly uses the enormous potential of our sun, photovoltaic energy. One of the most promising materials for emerging applications in the field of photovoltaics are the so-called kesterites, formed by the elements: Cu, Zn, Sn and Se; all of which are abundant and of low or null toxicity. The development of high efficiency cells based on kesterite faces several challenges related to the complex nature of this family of materials. Among them, the control of Sn that tends to form liquid and volatile species during the synthesis process having a strong exchange with the annealing atmosphere. In this work, the dynamics of Sn during the synthesis of the photovoltaic absorber, Cu2ZnSnSe4 (CZTSe), is investigated through a sequential process (Sputtering + Annealing). We compare the classical methodology where Sn is already incorporated in the solid precursor with a new and innovative solution in which Sn is partially incorporated in the vapour phase. The impact on the mechanism of CZTSe formation is investigated, as well as the properties of the layers and the characteristics of the finished device

Small atom doping: a synergistic strategy to reduce SnZn recombination center concentration in Cu2ZnSnSe4

Kesterite Cu2ZnSnS x Se4-x (CZTSSe) is among the most promising inorganic Earth-abundant thin-film photovoltaic technologies, although currently, the larger voltage deficit compared with more mature chalcogenide technologies is hampering solar-to-electricity conversion efficiency progress in these materials. Most of the latest reports agree on the CZTSSe defect structure as the main limitation for the open-circuit voltage. Small atom doping is suggested as an interesting strategy to reduce the concentration of defects without affecting secondary phase formation. Herein, an innovative approach based on the introduction of LiAlH4 and its further decomposition during the selenization process of CZTSe precursors, as a pathway for hydrogen and lithium/alkali transient doping, is explored. This process shows a strong beneficial influence on the crystal growth and solar cell device performance, especially with a significant improvement in V oc and fill factor. A reduction of nonradiative recombination and a remarkable fourfold increase in the carrier lifetime correlating with the reduction of the open-circuit voltage (V oc) deficit below 330¿mV is demonstrated. A mechanism on how small atoms (Li and H) interact to reduce the concentration of SnZn recombination centers while keeping doping relatively unchanged is proposed, opening fundamental perspectives for the simple and universal transient doping of thin-film chalcogenide compounds.Peer ReviewedPostprint (published version

Towards low cost and sustainable thin film thermoelectric devices based on quaternary chalcogenides

This is the peer reviewed version of the following article: Isotta, E. [et al.]. Towards low cost and sustainable thin film thermoelectric devices based on quaternary chalcogenides. "ADVANCED FUNCTIONAL MATERIALS", 20 Maig 2022, núm. 2202157, which has been published in final form at https://onlinelibrary.wiley.com/doi/10.1002/adfm.202202157. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.A major challenge in thermoelectrics (TEs) is developing devices made of sustainable, abundant, and non-toxic materials. Furthermore, the technological drive toward low sizes makes crucial the study of nano and micro configurations. In this work, thin film TE devices based on p-type Cu2+xZn1-xSnS4 and Cu2+xZn1-xSnSe4, and n-type AlyZn1-yO are fabricated by physical vapor deposition. The kesterite phases show good purity and promising TE power factor, likely enhanced by the copper–zinc order–disorder transition. Thin film generators in planar configuration are assembled by a sequential deposition of the p-type, n-type, and contact materials. The power per unit planar area reaches 153 and 279 nW cm-2 for the sulphur- and selenium-based generators, respectively. These values significantly outperform any other literature attempt based on sustainable and low-cost thin films. Furthermore, if compared with traditional TEs often made of scarce and toxic materials, these devices offer a cost reduction above 80%. This allows reaching comparable values of power density per unit material cost, representing a first real step toward the development of sustainable and non-toxic thin film TE devices. These can find applications in micro energy harvesters, microelectronics coolers, and temperature controllers for wearables, medical appliances, and sensors for the internet of things.A.J. thanks the European Social Fund+ for the FI fellowship. The authors would like to acknowledge the help of Dr. Mirco D’Incau, Dr. Narges Ataollahi, and Prof. Della Volpe for the design of the measuring setup, as well as useful discussion with Prof. Dario Narducci. This research has received funding from the Spanish Ministry of Science, Innovation and Universities under the MATER-ONE projects (PID2020-116719RB-C41). Authors from IREC belong to the SEMS (Solar Energy Materials and Systems) Consolidated Research Group of the “Generalitat de Catalunya” (ref. 2017 SGR 862) and are grateful to European Regional Development Funds (ERDF, FEDER Programa Competitivitat de Catalunya 2007–2013). M.G. acknowledges the financial support from Spanish Ministry of Science, Innovation and Universities within the Juan de la Cierva fellowship (IJC2018-038199-I). E.S. acknowledges the ICREA Academia Program. Open Access Funding provided by Universita degli Studi di Trento within the CRUI-CARE Agreement.Peer ReviewedPostprint (published version

Jardins per a la salut

Facultat de Farmàcia, Universitat de Barcelona. Ensenyament: Grau de Farmàcia. Assignatura: Botànica farmacèutica. Curs: 2014-2015. Coordinadors: Joan Simon, Cèsar Blanché i Maria Bosch.Els materials que aquí es presenten són el recull de les fitxes botàniques de 128 espècies presents en el Jardí Ferran Soldevila de l’Edifici Històric de la UB. Els treballs han estat realitzats manera individual per part dels estudiants dels grups M-3 i T-1 de l’assignatura Botànica Farmacèutica durant els mesos de febrer a maig del curs 2014-15 com a resultat final del Projecte d’Innovació Docent «Jardins per a la salut: aprenentatge servei a Botànica farmacèutica» (codi 2014PID-UB/054). Tots els treballs s’han dut a terme a través de la plataforma de GoogleDocs i han estat tutoritzats pels professors de l’assignatura. L’objectiu principal de l’activitat ha estat fomentar l’aprenentatge autònom i col·laboratiu en Botànica farmacèutica. També s’ha pretès motivar els estudiants a través del retorn de part del seu esforç a la societat a través d’una experiència d’Aprenentatge-Servei, deixant disponible finalment el treball dels estudiants per a poder ser consultable a través d’una Web pública amb la possibilitat de poder-ho fer in-situ en el propi jardí mitjançant codis QR amb un smartphone

SbSeI and SbSeBr micro-columnar solar cells by a novel high pressure-based synthesis process

Van der Waals chalcogenides and chalcohalides have the potential to become the next thin film PV breakthrough, owing to the earth-abundancy and non-toxicity of their components, and their stability, high absorption coefficient and quasi-1D structure, which leads to enhanced electrical anisotropic properties when the material is oriented in a specific crystalline direction. However, quasi-1D semiconductors beyond Sb2(S,Se)3, such as SbSeX chalcohalides, have been scarcely investigated for energy generation applications, and rarely synthesised by physical vapor deposition methodologies, despite holding the promise of widening the bandgap range (opening the door to tandem or semi-transparent devices), and showing enticing new properties such as ferroelectric behaviour and defect-tolerant nature. In this work, SbSeI and SbSeBr micro-columnar solar cells have been obtained for the first time by an innovative methodology based on the selective halogenation of Sb2Se3 thin films at pressure above 1 atm. It is shown that by increasing the annealing temperature and pressure, the height and density of the micro-columnar structures grows monotonically, resulting in SbSeI single-crystal columns up to 30 µm, and tuneable morphology. In addition, solar cell prototypes with substrate configuration have shown remarkable Voc values above 550 mV and 1.8 eV bandgap.Peer ReviewedPostprint (published version