Solution-processed organic devices developed by a novel cost-effective patterning technique based on electrical erosion

Application of arc erosion to the patterning of metallic contacts in organic devices is presented. A home-made systems and details of the working principles are described. Advantages and drawbacks of this novel technology are discussed

The use of arc-erosion as a patterning technique for transparent conductive materials

Within the framework of cost-effective patterning processes a novel technique that saves photolithographic processing steps, easily scalable to wide area production, is proposed. It consists of a tip-probe, which is biased with respect to a conductive substrate and slides on it, keeping contact with the material. The sliding tip leaves an insulating path (which currently is as narrow as 30 μm) across the material, which enables the drawing of tracks and pads electrically insulated from the surroundings. This ablation method, called arc-erosion, requires an experimental set up that had to be customized for this purpose and is described. Upon instrumental monitoring, a brief proposal of the physics below this process is also presented. As a result an optimal control of the patterning process has been acquired. The system has been used on different substrates, including indium tin oxide either on glass or on polyethylene terephtalate, as well as alloys like Au/Cr, and Al. The influence of conditions such as tip speed and applied voltage is discusse

Matriz de diodos electroluminiscentes orgánicos emisores en el infrarrojo cercano (1.54 μm) basados en complejos de erbio fabricados por métodos de bajo coste

[EN]: Solution processed 1.54 μm near infrared organic light-emitting diodes (NIR-OLED) based on novel Er(III) complexes, having the general formula[Er(β-diketonate) 3 (N,Ndonor)], have been manufactured by cost-effective methods and their properties studied. 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione (Htfnb or Hnta) or 1,1,1-trifuoro-5,5-dimethyl-2,4-hexanedione (Htpm) are the fluorinated β-diketonate primary sensitizers, and 2,2'-bipyridine (bipy) or 5-nitro-1,10-phenanthroline (5NO2phen) act as N,N-donors. The simple structure of the diodes is glass/indium-tin oxide (ITO)/poly (3,4-ethylenedioxythiophene)-poly(styrene sulfonate)/[Er-complex]/Ca/Al. The resulting electroluminescence corresponds with the 4I13/2→4I15/2 Er(III) emission at 1.54 μm and no visible emission is observed. Photophysical characterization proves that, upon organic ligand excitation by UV light, the luminescence from the ligands is totally quenched in favour of 4I13/2→4I15/2 Er(III) emission, confirming a complete resonant energy transfer from the ligands to the Er(III) ion, analogous to that observed in the electroluminescence emission. We present a fabrication method that avoids any photolithographic or mask step. The reported results showa simple way to obtain large area NIR-OLEDs by cost-effective methods. © Sociedad Española de Óptica.[ES]: Se han fabricado y caracterizado diodos orgánicos emisores de luz en el infrarrojo cercano (NIR-OLED) procesados desde solución, basados en nuevos complejos de Erbio (III) con fórmula general [Er(β-d)3(N,N-donor)] utilizando métodos de bajo coste. Los ligandos primarios son β-dicetonatos fluorados 4,4,4-trifluoro-1-(2-naftil)-1,3-butanodiona (Htfnb o Hnta) o 1,1,1-trifluoro -5,5-dimetil-2,4-hexanodiona (Htpm) y los ligandos secundarios 2,2’-bipiridina (bipy) o 5-nitro-1,10-fenantrolina (5NO2phen) actúan como bases de Lewis. La estructura del diodo es vidrio/óxido indio-estaño (ITO)/poli (3,4-etilendioxitiofeno)-poli (estireno sulfonato)/complejo de Er(III)/Calcio/Aluminio. La electroluminiscencia resultante corresponde con la emisión de la transición 4I13/2→4I15/2 del Er(III) a 1.5 μm sin que se observe emisión alguna en el visible. La caracterización fotofísica muestra que, bajo excitación con luz UV, se produce un apagamiento de la emisión de los ligandos acompañado por una emisión en el NIR del Er(III) análoga a la obtenida por excitación eléctrica, confirmando de este modo la transferencia completa de energía desde los ligandos al ion Er(III). Presentamos un método de fabricación que evita cualquier paso fotolitográfico con máscara. Los resultados reportados muestran un camino sencillo para obtener diodos emisores de luz en el infrarrojo cercano utilizando métodos de bajo coste.P. Martín-Ramos thanks the Spanish Ministry of Education and Santander Universidades JPI_2013 for their financial support. Comunidad Autónoma de Madrid under projects S2009/MAT-1756 and S2009/ESP-1781. Spanish Ministerio de Economía y Competitividad (MINECO) under projects MAT2012-37276-C03-03 and TEC2011-13635-E are gratefully acknowledged by C. Coya. CEMDRX group is grateful to the Fundação para Ciência e a Tecnologia (FCT) under grant PTDC/FIS/102284/2008. UVA group acknowledges financial support of Junta de Castilla y León through project VA300A12-1.Peer Reviewe

Effect of Pristine Graphene on Methylammonium Lead Iodide Films and Implications on Solar Cell Performance

The relatively low stability of solar cells based on hybrid halide perovskites is the main issue to be solved for the implementation in real life of these extraordinary materials. Degradation is accelerated by temperature, moisture, oxygen, and light and mediated by halide easy hopping. The approach here is to incorporate pristine graphene, which is hydrophobic and impermeable to gases and likely limits ionic diffusion while maintaining adequate electronic conductivity. Low concentrations of few-layer graphene platelets (up to 24 × 10–3 wt %) were incorporated to MAPbI3 films for a detailed structural, optical, and transport study whose results are then used to fabricate solar cells with graphene-doped active layers. The lowest graphene content delays the degradation of films with time and light irradiation and leads to enhanced photovoltaic performance and stability of the solar cells, with relative improvement over devices without graphene of 15% in the power conversion efficiency, PCE. A higher graphene content further stabilizes the perovskite films but is detrimental for in-operation devices. A trade-off between the possible sealing effect of the perovskite grains by graphene, that limits ionic diffusion, and the reduction of the crystalline domain size that reduces electronic transport, and, especially, the detected increase of film porosity, that facilitates the access to atmospheric gases, is proposed to be at the origin of the observed trends. This work demonstrated how the synergy between these materials can help to develop cost-effective routes to overcome the stability barrier of metal halide perovskites, introducing active layer design strategies that allow commercialization to take off.We acknowledge financial support by the Spanish Ministry of Science and Innovation under Projects PID2020-115514RB-I00 (C.C.), MAT2015-65356-C3-2-R (A.A), and PID2019-107314RB-I00 (I.M-S). This work was partially supported by European Research Council (ERC) via Consolidator Grant (724424-No-LIMIT) (I.M-S), AYUDA PUENTE 2020 URJC (C.C.). Associated Lab LABCADIO belonging to Community of Madrid, CM, net laboratories ref 351 is also acknowledged (C.C.). T.S.R. acknowledges funding from CM and European Social Fund (ESF) under the Talento fellowship 2017-T2/IND-5586 and project F660 financed by CM and Rey Juan Carlos University under action 1, “Encouragement of Young Phd students investigation". C.R-O. acknowledges funding from the Spanish Ministry of Science and Innovation under a FPI predoctoral contract (PRE2019-088433)

Influence of the substrate on the bulk properties of hybrid lead halide perovskite films

In addition to the known effect of the substrate on the interfacial properties of perovskite films, here we show that the bulk properties of hybrid lead halide perovskite films depend on the type of substrate used for film growth. Despite the relative large film thickness, ∼600 nm, the roughness and nature of the substrate layer (glass, FTO, TiO2 and PEDOT:PSS) affect not just the degree of preferential orientation and crystal grain size but also the lattice parameters of CH3NH3PbI3 films synthesized from the PbCl2 precursor. The obtained changes in lattice parameters indicate that the Pb–Pb distance varies by around 0.7%. We suggest that the substrate roughness and chemical nature determine the concentration of defects mainly by varying the chlorine content and probably by the incorporation of oxygen and iodine vacancies during film nucleation and growth. These differences also have consequences in the observed light induced transformations. Upon laser illumination, the formation of additional defects, most probably related to oxygen, is revealed by 110 and 165 cm−1 Raman peaks. With increasing laser power the chemical transformation into PbOx is clearly identified by the 140 and 275 cm−1 Raman peaks. The irreversible photoluminescence enhancement observed at low power with illumination time, also dependent on the substrate nature, is proposed to be due to the localization of the electron–hole excitons created in the vicinity of the light generated defects. These results shed light on the performance of the perovskite layer and help to understand how bulk processes, where ion migration is a conspicuous example, are severely affected by interfacial properties such as those imposed by the substrate.Funding by the Spanish Ministerio de Economía y Competitividad (MINECO) under Projects MAT2015-65356-C3-1-R and 2-R, MAT2014-54852-R and MAT2015-70611-ERC and Comunidad de Madrid Excellence Network under Project S2013/MIT-2740 (and Associated Lab LABCADIO belonging to CM net labs ref. 351) is acknowledged. We also acknowledge the MINECO for financial support and provision of synchrotron radiation facilities at ESRF, and thank María Vila for her assistance in using beamline BM25-SpLine. B. C. H. is grateful to the support of the National Council of Technological and Scientific Development (CNPq), Brazil, through the Science without Borders program

Microbiota intestinal en recién nacidos alimentados con lactancia materna exclusiva a 3824 m.s.n.m. Hospital III EsSalud Juliaca - 2020

La microbiota intestinal en recién nacidos alimentados con lactancia materna exclusiva a 3824 m s.n.m. Hospital III EsSalud Juliaca – 2020. La microbiota intestinal participa en eventos de homeostasis e inmunidad intestinal de trascendencia para la salud humana. Determinar la microbiota intestinal en RN alimentados con LME a 3824 m s.n.m. Aislar, Identificar y cuantificar las cepas de microorganismos en meconio de recién nacidos alimentados con lactancia materna exclusiva y determinar si existe diferencias entre la microbiota del RN con LME a nivel del mar y a una altitud de altitud de a 3824 m s.n.m. Estudio observacional, analítico, transversal, prospectivo: que incluyó 40 RN de parto vaginal de ambos sexos entre 37 y 41 semanas que recibieron LME, en los cuales se recolecto muestra de meconio al tercer día de nacido durante el periodo diciembre 2019 a febrero 2020. Se empleó dos tipos de medios de cultivo MRS y XLD, y medios diferenciales bioquímicos, para diferenciar a los microorganismos. Del 100% de muestras, se encontró: Lactobacillus sp en 95.0 %, Eschericha coli en 82,55 %, Lactococos sp. en 57,5 %, Bifidobacterium 32.5 %, Enterobacter sp 20.0, Proteus sp 7,5 %, %, Klebsiella sp 2,5%. Además se encontró que un 70% muestra un alto crecimiento bacteriano, 25% de crecimiento medio, y 5% de bajo crecimiento. A 3824 m.s.n.m. encontramos una colonización mayor en Lactobacillius sp. 95.00% y Escherichia coli 82,50%. En RN alimentados con LME a 3824 m s.n.m. encontramos alto porcentaje de Lactobacillus sp, Eschericha coli, Lactococos sp, y Bifidobacterium, y en menor porcentaje Enterobacter sp, Proteus sp, Klebsiella sp. Nuestros hallazgos en la altitud indican que existiría una mayor colonización de Bifidobacterium sp., y E. coli a diferencia de los hallazgos encontrados a 30 m s. n.m.Tesi

Charge transport and sensitized 1.5 μm electroluminescence properties of full solution-processed NIR-OLED based on novel Er(III) fluorinated β-diketonate ternary complex

et al.Solution-processed near-infrared organic light-emitting diodes (NIR-OLEDs) with structure glass/indium-tin oxide/poly(3,4-ethylenedioxythiophene)- poly(styrene sulfonate)/Er-complex/Ca/Al based on a novel Er(III) complex, [Er(tfnb)3(bipy)] (Htfnb = 4,4,4-trifluoro-1-(2-naphthyl)-1,3- butanedione and bipy = 2,2′-bipyridine) have been manufactured and their properties have been studied. A complete quenching of the organic ligand visible emission is shown, and only the sensitized 1.5 μm electroluminesce from Er(III) results. From the electrical characteristic we present the mobility dependence on applied voltage using a numerical model, comparing it to poly(9,9-dioctylfluorene), a commercial semiconducting polymer with optical properties close to those of the molecular ligands. The synthesis of the novel complex together with a detailed analysis of its structure elucidated by XRD, 1H NMR, Raman, and Fourier-transform infrared spectroscopies is presented. A wide-ranging characterization of its photophysical properties in terms of absorption and steady and transient photoluminescence is used to investigate the energy-transfer process from the organic ligand to the central Er(III) ion. © 2013 American Chemical Society.P. Martín-Ramos thanks the Spanish Ministry of Education for its financial support. Support by Comunidad Autónoma de Madrid under project S2009/MAT-1756 and by the Spanish Ministerio de Economía y Competitividad (MINECO) under projects MAT2012- 37276-C03-03 and TEC2011-13635-E is gratefully acknowledged by the URJC group. The CEMDRX group is grateful to the Fundação para a Ciência e a Tecnologia (FCT) for providing funds under grant PTDC/FIS/102284/2008. The UVA group acknowledges financial support of Junta de Castilla y León through project VA300A12-1.Peer Reviewe

Métodos de modificación de las propiedades fotorrefractivas en sistemas Bi12MO20

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Física de Materiales. Fecha de lectura: 22-05-1997Se han caracterizado monocristales con fórmula química nominal Bi ,,M J3 i, ,,.,,O isomorfos a la fase sillenita, en los que M es un ion no tetravalente, en concreto M= Ga " y Zn 2'. En estos materiales se propone que el Bi3' en sitios tetraédricos es el defecto mas abundante y que la compensación de carga se produce mediante vacantes aniónicas. Este defecto parece ser responsable de ciertas características espectroscópicas observadas. se ha estudiado el proceso de inhibición del efecto fotorrefractivo mediante el dopaje con Ga en Bi ,, Ti 0 ,,, así como el efecto de sustituir totalmente el ión tetravalente por Ga como caso límite de dicho proceso de inhibición. Por último, se ha estudiado la influencia que ejercen los tratamientos de reducción térmica en vacío sobre las propiedades fisicas de las sillenitas. Se ha establecido un modelo para la reducción de la superficie y se ha demostrado que dichos tratamientos influyen en el volumen del material y modifican sus propiedades fotorrefractivas.Bi ,$A$i ,,O ,, (M = Ga 3+, Zn '+) systems are isomorphous to the sillenite phase. It is proposed that Bi '+ in tetrahedal positions is the most abundant defect in these crystals and that charge compensation is produd by anionic vacancies . The inhibition process induced on the photorefractive effect by doping Bi ,,Ti O ,, with gallium has been characterized, as well as the case in which Ga completely replaces the tetravalent cation. Finally, the influence of thermal oxi-reduction treatments on the physical properties of sillenites has been investigated. It is concluded that this sort of treatments clearly have an influence in the crystal buUc and can madi@ the photorefractive properties of these crystals

Tetrahedral Cr4+ and Cr5+ in Bi12TiO20 single crystals

Cr-doped Bi12TiO20 (BTO) single crystals have been grown by the Czochralski technique. The optical absorption at 4.2 K of as-grown crystals is compared to that observed after vacuum annealing of the samples. This treatment modifies the visible and near infrared optical absorption. The absorption spectrum of Cr-doped BTO crystals before vacuum annealing is interpreted as the superposition of the crystal-field transition bands of (CrO4)4- and (CrO4)3- and charge transfer bands of (CrO4)3-. Annealing in vacuum leads to Cr5+ → Cr4+ conversion. Chromium reduction to lower oxidation states has not been observed. The optical absorption shows a vibrational character. The energy shifts of Cr4+ bands are as expected from the coupling with the T2(v3) fundamental mode of (CrO4)4- clusters. On the other hand, it is proposed that the series of sharp lines observed in the 9500 to 11500 cm-1 range arises from the interaction with a vibration of about 300 cm-1, which seems to be the T2(v4) fundamental mode of (CrO4)3- and with the lattice modes.Peer Reviewe

New triindole-based organic semiconductors: structure-property relationships

Trabajo presentado como comunicación al "IX Organic Field-Effect Transistors" celebrado en San Diego (USA) en Agosto del 2010.We introduce a new family of stable high-mobility organic π-type semiconductors based on the electron-rich 10,15- dihydro-5H-diindolo[3,2-a:3',2'-c]carbazole (triindole) extended π-conjugated system. This platform tends to form columnar stacks of the aromatic cores maximizing π-orbital overlap between adjacent molecules, thus paving the way for the one-dimensional migration of charge carriers along the columns. In addition these compounds have two different types of positions that can be functionalized independently offering the possibility of tuning their electronic properties as well as their morphology through chemical functionalization. The integration of the optimized triindole derivatives into solution processed devices as active layer is explored in this work.Financial support from the MEC (CTQ2007-65683/BQU and S2009/MAT-1756/CAM are gratefully acknowledged.Peer reviewe