Study of hole-transporter-free perovskite solar cells based on fully printable components

Hole-transporter-free perovskite solar cells carrying a carbon back contact electrode provide the possibility of making full printable low cost and stable devices, even though their efficiency is substantially lower than those made in the standard configuration. The present work searched for simple and easy routes for constructing such devices, demonstrating that organic components do enhance device efficiency but only to a level that is not worth the trouble nor the cost. Devices based on a triple mesoporous layer of titania/zirconia/carbon with perovskite infiltration gave an efficiency of 10.7%. After 180 days of storing under ambient conditions, a small loss of efficiency has been observed for a cell made in June, in spite of the fact that in going from June to December, a large increase of the ambient humidity took place, thus verifying the protective effect that the carbon electrode is providing. The addition of spiro-OMeTAD to the hole-transporter-free device resulted in increasing the efficiency by about 10%, a change which is appreciated to be of low importance given the cost of this material. This increase mainly derived from an increase in the current. Devices of different sizes have been constructed by screen printing, using home-made pastes for all the components making the cell scaffold, i.e., for titania, zirconia, and carbon layers

Manufacturing Resilience during the Coronavirus Pandemic: On the investigation Manufacturing Processes Agility

The unprecedented events that worldwide population experienced during year 2020 due to the COVID-19 pandemic, resulted in the formation of numerous challenges across the majority of aspects of every day life. Manufacturing industries and supply chain networks faced a unique decostruction during this period due to restrictions created by global or local lockdowns. Reduction of human resources availability and transportation restrictions linked with the extreme and rapid increase of demand for medical supplies led manufactring related activities to reach their limits. Moreover, the non flexible manufacturing methods that are employed for the production of this type of equipment as well as the delayed delivery of products that are used as raw material at the early production stages, resulted in market shortage of medical supplies while demand constantly growing. Additive Manufacturing was used for the immediate production of plastic/metal medical equipment, taking advantage of reverse engineering, process flexibility and commercialization of printing devices. Small and large enteprises in cooperation with individuals have been organized into Local Hubs in order to reduce the transportation time and accelerate the supply of the required equipment at local hopitals until the the non flexible production lines manage to produce the desired production volume under the required production rate. This study aims to identify reasons why traditional manufacturing facilies faced such difficulties in the production of medical equipment and to propose a framework where Additive Manufacturing methods can be used for the immediate, local and low volume production of the desired product, giving time to non easily adjustable industries to initiate the mass production

Photoelectrochemical cell for simultaneous electricity generation and heavy metals recovery from wastewater

The feasibility of simultaneous recovery of heavy metals from wastewater (e.g., acid mining and electroplating) and production of electricity is demonstrated in a novel photoelectrochemical cell (PEC). The photoanode of the cell bears a nanoparticulate titania (TiO2) film capped with the block copolymer [poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol)] hole scavenger, which consumed photogenerated holes, while the photogenerated electrons transferred to a copper cathode reducing dissolved metal ions and produced electricity. Dissolved silver Ag+, copper Cu2+, hexavalent chromium as dichromate Cr2O72− and lead Pb2+ ions in a mixture (0.2 mM each) were removed at different rates, according to their reduction potentials. Reduced Ag+, Cu2+ and Pb2+ ions produced metal deposits on the cathode electrode which were mechanically recovered, while Cr2O72− reduced to the less toxic Cr3+ in solution. The cell produced a current density Jsc of 0.23 mA/cm2, an open circuit voltage Voc of 0.63 V and a maximum power density of 0.084 mW/cm2. A satisfactory performance of this PEC for the treatment of lead-acid battery wastewater was observed. The cathodic reduction of heavy metals was limited by the rate of electron-hole generation at the photoanode. The PEC performance decreased by 30% after 9 consecutive runs, caused by the photoanode progressive degradation

Experimental and theoretical investigation of the mechanism of the reduction of O2 from air to O22– by VIVO2+–N,N,N-amidate compounds and their potential use in fuel cells

The two-electron reductive activation of O2 to O22– is of particular interest to the scientific community mainly due to the use of peroxides as green oxidants and in powerful fuel cells. Despite of the great importance of vanadium(IV) species to activate the two-electron reductive activation of O2, the mechanism is still unclear. Reaction of VIVO2+ species with the tridentate-planar N,N,N-carboxamide (ΗL) ligands in solution (CH3OH:H2O) under atmospheric O2, at room temperature, resulted in the quick formation of [VV(═O)(η2-O2)(κ3-L)(H2O)] and cis-[VV(═O)2(κ3-L)] compounds. Oxidation of the VIVO2+ complexes with the sterically hindered tridentate-planar N,N,N-carboxamide ligands by atmospheric O2 gave only cis-[VV(═O)2(κ3-L)] compounds. The mechanism of formation of [VV(═O)(η2-O2)(κ3-L)(H2O)] (I) and cis-[VV(═O)2(κ3-L)] (II) complexes vs time, from the interaction of [VIV(═O)(κ3-L)(Η2Ο)2]+ with atmospheric O2, was investigated with 51V, 1H NMR, UV–vis, cw-X-band EPR, and 18O2 labeling IR and resonance Raman spectroscopies revealing the formation of a stable intermediate (Id). EPR, MS, and theoretical calculations of the mechanism of the formation of I and II revealed a pathway, through a binuclear [VIV(═O)(κ3-L)(H2O)(η1,η1-O2)VIV(═O)(κ3-L)(H2O)]2+ intermediate. The results from cw-EPR, 1H NMR spectroscopies, cyclic voltammetry, and the reactivity of the complexes [VIV(═O)(κ3-L)(Η2Ο)2]+ toward O2 reduction fit better to an intermediate with a binuclear nature. Dynamic experiments in combination with computational calculations were undertaken to fully elucidate the mechanism of the O2 reduction to O22– by [VIV(═O)(κ3-L)(Η2Ο)2]+. The galvanic cell {Zn|VIII,VII||Id, [VIVO(κ3-L)(H2O)2]+|O2|C(s)} was manufactured, demonstrating the important applicability of this new chemistry to Zn|H2O2 fuel cells technology generating H2O2 in situ from the atmospheric O2

Parenting and psychosocial adjustment of children in school: identifying individual, perental and family factors

The present study examines the relation between parenting and psychosocial adjustment in the school. The sample consists of 349 11-and 12-year-old preadolescents from the fifth and sixth grade. Data were collected by three informants: teachers [psychosocial adjustment, Test of Psychosocial Adjustment (teachers scale)], parents [general functioning (McMaster FAD), attachment type (RSQ), children's personality (Children and Adolescents Personality Dimensions)] and preadolescents [parenting (EMBU-C) and demographic data].findings indicate that children's gender, class and personality dimensions (apart from Agreeableness) differentiate the way parents manage their offspring. Concerning parental characteristics significant differences were produced between mothers and fathers, between the education levels of the parents and the type of parental attachment. Family context variables (general functioning, divorce, disease) were also related to parenting. Psychological adjustment was associated to children's gender, birth order, country of origin as well as personality factors. Parental characteristics such as profession, mothers' age and attachment type were associated to adjustment. Finally, only family functioning was related to psychosocial adjustment. Findings are discussed under the prism of effective prevention and intervention procedures for adjustment difficulties in the school setting.Η παρούσα εργασία εξετάζει τη σχέση ανάμεσα στις γονικές πρακτικές διαπαιδαγώγησης και την ψυχοκοινωνική προσαρμογή στο σχολείο. Το δείγμα αποτελείται από 349 προεφήβους 11 και 12 ετών, μαθητές Ε΄και Στ΄Δημοτικού. Τα δεδομένα περισυλλέγησαν από τρεις διαφορετικές πηγές: τους εκπαιδευτικούς [ψυχοκοινωνική προσαρμογή στο σχολείο, Εργαλείο Ψυχοκοινωνικής Προσαρμογής Παιδιών Προσχολικής και Σχολικής Ηλικίας-Τεστ Ψυχοκοινωνικής Προσαρμογής (κλίμακα εκπαιδευτικών για παιδιά 7-12 ετών)], τους γονείς [γενική λειτουργία οικογένειας (Ερωτηματολόγιο Λειτουργίας της Οικογένειας, Mc Master FAD)], τύπος δεσμού (Ερωτηματολόγιο Σχέσεων, RSQ), προσωπικότητα παιδιού [Ερωτηματολόγιο «Διαστάσεις Προσωπικότητας για Παιδιά και Εφήβους», Ε-ΔΙΠΡΟΠΕ12)] και τα παιδιά [γονικές πρακτικές (Ερωτηματολόγιο EMBU-C), δημογραφικά χαρακτηριστικά οικογένειας].Τα ευρήματα μπορούν να συνοψιστούν στα εξής: το φύλο του παιδιού, η τάξη φοίτησης και οι διαστάσεις της προσωπικότητας, πλην της προσήνειας, βρέθηκαν να διαφοροποιούν σημαντικά τον τρόπο που εξασκούν οι γονείς τη διαπαιδαγώγηση στην οικογένειά τους. Από τα ατομικά χαρακτηριστικά των γονέων, μόνο το φύλο, η βαθμίδα εκπαίδευσης και ο τύπος δεσμού που συνάπτουν οι γονείς βρέθηκαν να διαφοροποιούν σημαντικά τον τρόπο που εφαρμόζονται στην οικογένεια οι γονικές πρακτικές διαπαιδαγώγησης. Οι τρεις μεταβλητές του οικογενειακού πλαισίου που μελετήθηκαν βρέθηκαν να επιδρούν στις γονικές πρακτικές. Η ψυχολογική προσαρμογή των παιδιών στο σχολείο βρέθηκε να επηρεάζεται από το φύλο, τη σειρά γέννησης και τη χώρα γέννησης του παιδιού, όπως και από τις πέντε διαστάσεις της προσωπικότητάς του. Τα χαρακτηριστικά των γονέων που βρέθηκαν να επιδρούν στην ψυχοκοινωνική προσαρμογή του παιδιού στο σχολείο είναι το επάγγελμα των δυο γονέων, η ηλικία της μητέρας, αλλά και ο τύπος δεσμού που συνάπτουν και οι δύο γονείς. Τέλος, μόνο η γενική λειτουργία της οικογένειας συσχετίστηκε με την προσαρμογή στο σχολείο.Τα δεδομένα της παρούσας έρευνας συζητούνται και προτείνονται παρεμβάσεις για αποτελεσματική πρόληψη και αντιμετώπιση δυσκολιών προσαρμογής στο σχολικό πλαίσιο

Organic/inorganic nanocomposite gels employed as electrolyte supports in Dye-sensitized Photoelectrochemical cells

Dye-sensitized photoelectrochemical cells based on TiO2 mesoporous films, a ruthenium bipyridyl derivative as photosensitizer and a SiO2/poly(ethylene glycol)-200 nanocomposite thin film as electrolyte support, have been constructed. TiO2 films have been deposited on conductive transparent Indium-Tin Oxide glass slides by means of a sol-gel procedure carried out in reverse-micellar solutions. The photosensitizer has been adsorbed on titania films from ethanolic solutions while the electrolyte layer has been synthesized by a sol-gel procedure. The presence of silica in the nanocomposite electrolyte gel provides the gelifying agent, the compound that holds the cell together in a sandwich form and the sealing agent that protects the cell and secures its long-term function. PEG-200 makes the organic subphase which provides the ionic conductivity. The present work describes the construction of the cell and the study of its efficiency. A variant of the cell has also been made by incorporating Ag+ and Ru3+ ions into titania particles, but these dopants did not improve cell efficiency, either in their oxidized or in their reduced form

Photoactivated Fuel Cells (PhotoFuelCells). An alternative source of renewable energy with environmental benefits

This work is a short review of Photoactivated Fuel Cells, that is, photoelectrochemical cells which consume an organic or inorganic fuel to produce renewable electricity or hydrogen. The work presents the basic features of photoactivated fuel cells, their modes of operation, the materials, which are frequently used for their construction and some ideas of cell design both for electricity and solar hydrogen production. Water splitting is treated as a special case of photoactivated fuel cell operation