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19 results on '"Tejada, Alvaro"'

3. Indirect excitation and luminescence activation of Tb doped indium tin oxide and its impact on the host’s optical and electrical properties

Author

Llontop, Paul, primary, Torres Fernandez, Carlos Enrique, additional, Piñeiro, Miguel, additional, Conde, Luis, additional, Tejada, Alvaro, additional, Palomino Töfflinger, Jan Amaru, additional, Rumiche, Francisco Aurelio, additional, Aragón, F. F. H., additional, Pacheco-Salazar, D. G., additional, Grieseler, Rolf, additional, Korte, Lars, additional, and Guerra, Jorge Andres, additional

Published
2022
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8. Erratum: Analysis of the physical and photoelectrochemical properties of c-Si(p)/a-SiC:H(p) photocathodes for solar water splitting (2021 J. Phys. D: Appl. Phys. 54 195101)

Author

Mejia, María del Carmen, primary, Sánchez, Luis Francisco, additional, Kurniawan, Mario, additional, Eggert, Lara, additional, Tejada, Alvaro, additional, Camargo, Magali, additional, Grieseler, Rolf, additional, Rumiche, Francisco, additional, Díaz, Isabel, additional, Bund, Andreas, additional, and Guerra, Jorge Andrés, additional

Published
2021
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9. Analysis of the physical and photoelectrochemical properties of c-Si(p)/a-SiC:H(p) photocathodes for solar water splitting

Author

Carmen Mejia, María del, primary, Sánchez, Luis Francisco, additional, Kurniawan, Mario, additional, Eggert, Lara, additional, Tejada, Alvaro, additional, Camargo, Magali, additional, Grieseler, Rolf, additional, Rumiche, Francisco, additional, Díaz, Isabel, additional, Bund, Andreas, additional, and Guerra, Jorge Andrés, additional

Published
2021
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10. Rapid Scalable Processing of Tin Oxide Transport Layers for Perovskite Solar Cells

Author

Smith, Joel A., primary, Game, Onkar S., additional, Bishop, James E., additional, Spooner, Emma L. K., additional, Kilbride, Rachel C., additional, Greenland, Claire, additional, Jayaprakash, Rahul, additional, Alanazi, Tarek I., additional, Cassella, Elena J., additional, Tejada, Alvaro, additional, Chistiakova, Ganna, additional, Wong-Stringer, Michael, additional, Routledge, Thomas J., additional, Parnell, Andrew J., additional, Hammond, Deborah B., additional, and Lidzey, David G., additional

Published
2020
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11. Hybrid Perovskite Degradation from an Optical Perspective: A Spectroscopic Ellipsometry Study from the Deep Ultraviolet to the Middle Infrared.

Author

Tejada, Alvaro, Peters, Sven, Al‐Ashouri, Amran, Turren‐Cruz, Silver Hamill, Abate, Antonio, Albrecht, Steve, Ruske, Florian, Rech, Bernd, Guerra, Jorge Andrés, and Korte, Lars

Subjects
*ELLIPSOMETRY, *PEROVSKITE
Abstract

A quantitative analysis of the thermally induced degradation of various device‐relevant multi‐cation hybrid perovskite films is performed using spectroscopic ellipsometry, for temperatures between 80 and 120 °C. The studied compositions are a triple cation perovskite Cs0.05(MA0.17FA0.83)0.95Pb(Br0.17I0.83)3, a Rb‐containing variant Rb0.05Cs0.05(MA0.17FA0.83)0.90Pb(Br0.17I0.83)3, and a methylammonium‐free Rb0.05Cs0.10FA0.85PbI3 composition. A very wide combined spectral range of 200 nm to 25 μm is covered by combining the data from two separate instruments. The relative changes in organic cation concentrations are quantified from the middle infrared molecular absorption bands, leveraging the use of point‐by‐point fitting for increased sensitivity. Additionally, the formation of PbI2 and non‐perovskite δ‐CsPbI3 phases is evidenced from Bruggemann effective medium fits to the visible and ultraviolet complex refractive indices. Methylammonium is almost completely depleted from the relevant compositions within 100 to 285 min of thermal annealing. The MA‐free perovskite degrades faster at intermediate temperatures, which is attributed to phase instability due to the formation of δ‐CsPbI3 in addition to PbI2. [ABSTRACT FROM AUTHOR]

Published
2022
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12. Cs(x)FA(1-x)Pb(l(1-y)Br(y))(3) Perovskite Compositions

Author

Braunger, Steffen, Mundt, Laura E., Wolff, Christian M., Mews, Mathias, Rehermann, Carolin, Jost, Marko, Tejada, Alvaro, Eisenhauer, David, Becker, Christiane, Andres Guerra, Jorge, Unger, Eva, Korte, Lars, Neher, Dieter (Prof. Dr.), Schubert, Martin C., Rech, Bernd, and Albrecht, Steve

Subjects
Institut für Physik und Astronomie, ddc:530
Abstract

We report on the formation of wrinkle-patterned surface morphologies in cesium formamidinium-based Cs(x)FA(1-y)Pb(I1-yBry)(3) perovskite compositions with x = 0-0.3 and y = 0-0.3 under various spin-coating conditions. By varying the Cs and Br contents, the perovskite precursor solution concentration and the spin-coating procedure, the occurrence and characteristics of the wrinkle-shaped morphology can be tailored systematically. Cs(0.17)FA(0.83)Pb(I0.83Br0.17)(3) perovskite layers were analyzed regarding their surface roughness, microscopic structure, local and overall composition, and optoelectronic properties. Application of these films in p-i-n perovskite solar cells (PSCs) with indium-doped tin oxide/NiOx/perovskite/C-60/bathocuproine/Cu architecture resulted in up to 15.3 and 17.0% power conversion efficiency for the flat and wrinkled morphology, respectively. Interestingly, we find slightly red-shifted photoluminescence (PL) peaks for wrinkled areas and we are able to directly correlate surface topography with PL peak mapping. This is attributed to differences in the local grain size, whereas there is no indication for compositional demixing in the films. We show that the perovskite composition, crystallization kinetics, and layer thickness strongly influence the formation of wrinkles which is proposed to be related to the release of compressive strain during perovskite crystallization. Our work helps us to better understand film formation and to further improve the efficiency of PSCs with widely used mixed-perovskite compositions.

Published
2018

13. Analysis of the physical and photoelectrochemical properties of c-Si(p)/a-SiC:H(p) photocathodes for solar water splitting.

Author

del Carmen Mejia, María, Sánchez, Luis Francisco, Kurniawan, Mario, Eggert, Lara, Tejada, Alvaro, Camargo, Magali, Grieseler, Rolf, Rumiche, Francisco, Díaz, Isabel, Bund, Andreas, and Guerra, Jorge Andrés

Subjects
SILICON solar cells, PHOTOELECTROCHEMICAL cells, ALUMINUM films, SILICON carbide thin films, HYDROGENATED amorphous silicon, PHOTOCATHODES, SPACE charge, CHARGE transfer
Abstract

The photoelectrochemical (PEC) properties of sputtered aluminum doped hydrogenated amorphous silicon carbide thin films grown on p-type crystalline silicon substrates were investigated in 1 M solution under chopped light illumination. Optical and structural properties of the top absorber layer were systematically assessed after post-deposition isochronical annealing treatments. Samples exhibited a noticeable improvement of the opto-electronic properties after thermal treatments. In addition, an abrupt enhancement of the photocurrent was observed reaching a saturation value of 17 mA cm−2 at −1.75 V vs. Ag/AgCl (3.5 M KCl). In this research we propose that this enhancement effect is associated to a charge transfer kinetic mechanism influenced by surface states and the p-type substrate. The latter most likely due to the space charge region extending beyond the absorber layer reaching the substrate. Current density-potential and electrochemical impedance spectroscopy measurements in dark revealed a reduction of the native layer at cathodic potentials higher than −1 V vs. Ag/AgCl (3.5 M KCl), which contributes to the high charge transfer kinetic of the system. We believe that these results will contribute to understand the substrate influence in the PEC performance of top absorber layers in multilayer structures for solar water splitting. [ABSTRACT FROM AUTHOR]

Published
2021
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14. CsxFA1–xPb(I1–yBry)3 Perovskite Compositions: the Appearance of Wrinkled Morphology and its Impact on Solar Cell Performance

Author

Braunger, Steffen, primary, Mundt, Laura E., additional, Wolff, Christian M., additional, Mews, Mathias, additional, Rehermann, Carolin, additional, Jošt, Marko, additional, Tejada, Alvaro, additional, Eisenhauer, David, additional, Becker, Christiane, additional, Guerra, Jorge Andres, additional, Unger, Eva, additional, Korte, Lars, additional, Neher, Dieter, additional, Schubert, Martin C., additional, Rech, Bernd, additional, and Albrecht, Steve, additional

Published
2018
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15. Erratum: Analysis of the physical and photoelectrochemical properties of c-Si(p)/a-SiC:H(p) photocathodes for solar water splitting (2021 J. Phys. D: Appl. Phys.54 195101).

Author

del Carmen Mejia, María, Sánchez, Luis Francisco, Kurniawan, Mario, Eggert, Lara, Tejada, Alvaro, Camargo, Magali, Grieseler, Rolf, Rumiche, Francisco, Díaz, Isabel, Bund, Andreas, and Guerra, Jorge Andrés

Subjects
PHOTOCATHODES, REDUCTION potential, SOLAR cells, ELECTRONIC journals
Abstract

Ph y s. 54 (2021) 26960 1 (3pp) ht tps://doi.or g/1 0.1 088/1 361-6463/abef ee Er r at um: Anal y sis of the ph y sical and phot oelectr oc hemical pr oper ties of c-Si(p)/a-SiC:H(p) phot ocathodes f or solar w at er split ting (2021 J. Ph y s. D: Appl. J our nal of Ph y sics D: Applied Ph y sics J. Ph y s. D: Appl. Erratum: Analysis of the physical and photoelectrochemical properties of c-Si(p)/a-SiC:H(p) photocathodes for solar water splitting (2021 J. Phys. [Extracted from the article]

Published
2021
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16. CsxFA1–xPb(I1–yBry)3Perovskite Compositions: the Appearance of Wrinkled Morphology and its Impact on Solar Cell Performance

Author

Braunger, Steffen, Mundt, Laura E., Wolff, Christian M., Mews, Mathias, Rehermann, Carolin, Jošt, Marko, Tejada, Alvaro, Eisenhauer, David, Becker, Christiane, Guerra, Jorge Andres, Unger, Eva, Korte, Lars, Neher, Dieter, Schubert, Martin C., Rech, Bernd, and Albrecht, Steve

Abstract

We report on the formation of wrinkle-patterned surface morphologies in cesium formamidinium-based CsxFA1–xPb(I1–yBry)3perovskite compositions with x= 0–0.3 and y= 0–0.3 under various spin-coating conditions. By varying the Cs and Br contents, the perovskite precursor solution concentration and the spin-coating procedure, the occurrence and characteristics of the wrinkle-shaped morphology can be tailored systematically. Cs0.17FA0.83Pb(I0.83Br0.17)3perovskite layers were analyzed regarding their surface roughness, microscopic structure, local and overall composition, and optoelectronic properties. Application of these films in p–i–n perovskite solar cells (PSCs) with indium-doped tin oxide/NiOx/perovskite/C60/bathocuproine/Cu architecture resulted in up to 15.3 and 17.0% power conversion efficiency for the flat and wrinkled morphology, respectively. Interestingly, we find slightly red-shifted photoluminescence (PL) peaks for wrinkled areas and we are able to directly correlate surface topography with PL peak mapping. This is attributed to differences in the local grain size, whereas there is no indication for compositional demixing in the films. We show that the perovskite composition, crystallization kinetics, and layer thickness strongly influence the formation of wrinkles which is proposed to be related to the release of compressive strain during perovskite crystallization. Our work helps us to better understand film formation and to further improve the efficiency of PSCs with widely used mixed-perovskite compositions.

Published
2018
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18. Lectura y bibliotecas escolares en el Perú: Reflexiones y experiencias desde el sur del país

Author

Tejada, Alvaro and Tejada, Alvaro

Abstract

El presente artículo presenta una visión general sobre las actividades que se vienen implementando en el tema de la lectura y las bibliotecas escolares en el Perú, los retos y avances que se enfrentan en un contexto de emergencia educativa nacional. Aborda la situación en que están inmersos los servicios de bibliotecas escolares y los retos que tienen que enfrentar para superar las dificultades y convertirse en servicios óptimos e indispensables para la educación. Analiza como los manifiestos de la IFLA ¿ UNESCO apoyan la gestión moderna de la biblioteca escolar. Al final se presentan actividades desarrolladas por la biblioteca escolar del CEP ¿Juan Vélez de Córdova¿ en un marco de cooperación interinstitucional y de apoyo social.

Published
2006

19. Informe y estudio sobre un almacén de materias primas en el Carmen de Viboral Antioquia : informe sobre visita

Author

Rojas Tejada, Alvaro, asesor and Colombia. Ministerio de Desarrollo Económico. Artesanías de Colombia

Subjects
Materias primas, Comercio
Abstract

6 hojas., Informe de visita de diagnóstico a un conjunto de talleres artesanales ceramistas del municipio de Carmen de Viboral (Antioquia), que se consideran representativos del promedio y de los cuales se hacen las respectivas descripciones sintéticas de sus características estructurales y funcionales, administrativas y tecno-productivas y en relación con las calidades, las dimensiones y el color aplicado a los productos. Uno de los objetivos de la visita fue cotizar con base en requerimientos de calidad y precios. Se enumeran las limitaciones comunes en la mayoría de las unidades de producción para el cumplimiento del volumen solicitado que destacó los problemas de la disposición de materia prima. El informe enuncia la realización de una reunión en la que se describieron los problemas locales de la producción artesanal señalando cada uno de los talleres informantes. Las conclusiones registradas constituyen un diagnóstico de la situación tecno- económica de la mayoría de los talles de la localidad. Se describe la gestión de consecución de local ante la administración del municipio para el montaje del almacén de materias primas., Disponible también en formato impreso.

Published
1974

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