Singular Temperatures Connected to Charge Transport Mechanism Transitions in Perylene Bisimides from Steady-State Photocurrent Measurements

Perylene bisimides (PBIs) are n-type semiconducting and photogenerating materials widely used in a variety of optoelectronic devices. Particularly interesting are PBIs that are simultaneously water-soluble and liquid-crystalline (PBI-W+LC) and, thus, attractive for the development of high-performing easily processable applications in biology and “green” organic electronics. In this work, singular temperatures connected to charge transport mechanism transitions in a PBI-W+LC derivative are determined with high accuracy by means of temperature-dependent photocurrent studies. These singular temperatures include not only the ones observed at 60 and 110 °C, corresponding to phase transition temperatures from crystalline to liquid-crystalline (LC) and from LC to the isotropic phase, respectively, as confirmed by differential scanning calorimetry (DSC), but also a transition at 45 °C, not observed by DSC. By analyzing the photocurrent dependence simultaneously on temperature and on light intensity, this transition is interpreted as a change from monomolecular to bimolecular recombination. These results might be useful for other semiconducting photogenerating materials, not necessarily PBIs or even organic semiconductors, which also show transport behavior changes at singular temperatures not connected with structural or phase transitions.We appreciate support from the Spanish government (MINECO) and the European Community (FEDER) through Grant MAT-2011-28167-C02-01, as well as the University of Alicante. We gratefully acknowledge financial support from MINECO (MAT2014-52305-P) and the UCM-BSCH joint project (GR3/14-910759). A. de la Peña thanks Universidad Complutense for a predoctoral fellowship

Distributed feedback lasers based on dichromated poly(vinyl alcohol) reusable surface-relief gratings

A simple, low-cost and versatile holographic method to produce reusable surface-relief gratings on dichromated poly(vinyl alcohol) (DCPVA) films, with periods Λ ≥ 270 nm and modulation depths up to 300 nm, is reported. DCPVA presents processing advantages with respect to other photoresists, such as dichromated gelatine, i.e. higher light sensitivity, simpler fabrication process and better batch to batch reproducibility. The successful use of these DCPVA relief gratings as distributed feedback (DFB) laser resonators is demonstrated. Second-order DFB devices emitting in the wavelength range 577-614 nm have been easily prepared by coating a dye-doped polymer film on top of the resonators.We thank the Spanish Government (MINECO) and the European Union (FEDER) for grant no. MAT2011-28167-C02

Sub-400 nm film thickness determination from transmission spectra in organic distributed feedback lasers fabrication

The design and fabrication of thin-film based organic optoelectronic devices require knowledge of the film optical properties. A low-cost and non-destructive method often used for optical characterization of films is the well-established spectrophotometric envelope method. However, this method is typically limited to thickness above 400 nm, a value often higher than that of the films involved in these devices. This paper studies a procedure to obtain the thickness of sub-400 nm active films from their spectrophotometric trace when the refractive index is previously known. The proposed procedure is based on comparing the experimental transmission spectrum in the transparent spectral window with that obtained by simulation. The capabilities of the proposed method are demonstrated here by its application in the fabrication of organic distributed feedback lasers, for which a fine control of film thickness is important to obtain an optimized and reproducible response. Results are verified with other techniques, such as ellipsometry and profilometry. Thus, with the proposed method, film thickness can be easily determined down to 40 nm maintaining an accuracy of about 5 nm even for films with low refractive index (1.5–1.7). Different methods to determine refractive index of these films are also discussed.Spanish Ministry of Economy and Competitivity (MINECO) and European Community (FEDER) through grant no. MAT2015-66586-R

Perylenediimide-based distributed feedback lasers with holographic relief gratings on dichromated gelatine

One dimensional second-order distributed feedback (DFB) lasers consisting of polystyrene (PS) films doped with a perylenediimide laser dye, deposited over dichromated gelatine (DCG) photoresist layers with solvent resistant relief gratings recorded by holographic lithography, are reported. The advantage of using the grating on DCG in the final device is that the fabrication process is simplified and the grating pattern better preserved, since no etching methods to transfer the grating to another substrate are needed. A very simple model, proposed to explain the experimental waveguide properties, has allowed identifying the waveguide mode at which DFB emission appears, which was the key to optimize the device performance. In the frame of this model, the thickness of the PS and DCG films could be adjusted in order to minimize the laser threshold and to control its wavelength tuneability. The performance of these lasers is comparable to that of recently reported devices based on the same active material, but deposited over high-quality DFB gratings engraved on SiO2 by nanoimprint lithography.We thank support from the Spanish Government (MINECO) and the European Community (FEDER) through Grant Nos. MAT2008-06648-C02 and MAT-2011-28167-C02, as well as to the University of Alicante. M.G.R. was supported by a CSIC fellowship within the program JAE

Grado en Química: coordinación y seguimiento del curso 2014-15

En la red docente "Seguimiento del grado en Química", formada por los coordinadores de las comisiones de semestre de la Facultad de Ciencias y la coordinadora del grado en Química, se ha analizado la información extraída de las reuniones periódicas (al menos dos por semestre) de las ocho comisiones de semestre (correspondientes a los cuatro cursos del grado en Química). El objetivo es conseguir una coherencia tanto en la distribución de contenidos, como en las metodologías docentes y de evaluación de las materias que componen el plan de estudios del Grado en Química de la Universidad de Alicante. Los resultados de este trabajo están permitiendo identificar problemas y plantear propuestas de mejora en la organización docente de la titulación. El trabajo realizado por la red se está utilizando para elaborar el autoinforme para la reacreditación del grado en Química

Distributed feedback lasers based on perylenediimide dyes for label-free refractive index sensing

The refractive index sensing capabilitity of distributed feedback (DFB) lasers based on highly photostable (under ambient conditions) perylenediimide-based active films, are reported. The sensor bulk sensitivity is determined from changes in the laser emission wavelength upon exposure to different liquids. The role of the active film thickness (hf) on the sensor sensitivity and on the laser parameters is studied. Sensors based on very thin films (hf = 160 nm) show the highest sensitivities, but their laser thresholds are relatively high and their operational durabilities moderate. The use of thicker films (hf = 850 nm) allows reducing the laser threshold and increasing the durability by two orders of magnitude. In this case, a higher sensitivity is achieved when the sensor operates at the wavelength corresponding to the first-order TE1 mode, instead of at the TE0 one. Finally, it is also shown that the inclusion of a high refractive index TiO2 layer on top of the sensor structure improves the sensitivity by around two times.This work was supported by the Spanish Government (MINECO) and the European Community (FEDER) through grant no. MAT-2011–28167-C02. This work was partially funded by the Basque Government within the framework of the Etortek Program (Grant No. IE13-360). M. Morales-Vidal has been partly supported by a MINECO FPI fellowship (no. BES-2009-020747)

Seguimiento del Grado en Química

Con la implantación del 4º curso del grado en Química, que se ha realizado en el presente curso académico, se han completado los cuatro cursos del grado. En la Facultad de Ciencias se han constituido ocho comisiones de semestre, en las que participan profesores de todos los departamentos que imparten docencia en la titulación y la Comisión de Grado, formada por los coordinadores de las comisiones de semestre que, a su vez, forman parte de una red docente para el seguimiento del grado. Desde estas comisiones se está realizando un intenso trabajo cooperativo cuyo objetivo es alcanzar una coherencia tanto en la distribución de contenidos, como en las metodologías docentes y de evaluación de las materias que componen el plan de estudios del Grado en Química de la Universidad de Alicante. La coordinación horizontal entre semestres de un mismo curso y la coordinación vertical entre cursos forman parte de las tareas que se desarrollan. Los resultados de este trabajo permiten identificar las deficiencias en el proceso de implantación y plantear posibles propuestas de mejora en la organización docente de la titulación

1,7-Bay-Substituted Perylenediimide Derivative with Outstanding Laser Performance

Efficient ASE at wavelengths >620 nm from PS films doped with a bay-substituted perylenediimide (PDI) derivative is reported. The maximum PDI content is around 40 times larger than in prior studies. The ability to introduce large dye amounts into the film without photoluminescence (PL) quenching allows very high PL and ASE efficiencies with low thresholds. A distributed feedback (DFB) laser device using one of the best-performing films is fabricated and characterized.We thank support from the Spanish Government (MINECO), the European Community (FEDER) and the Generalitat Valenciana through MAT-2011–28167-C02, CTQ2011–26455, PROMETEO 2012/010 and ISIC/2012/008, as well as to the University of Alicante and the University Miguel Hernández de Elche

Controlling the emission properties of solution-processed organic distributed feedback lasers through resonator design

Surface-emitting distributed feedback (DFB) lasers with both, resonator and active material based on solution-processable polymers, are attractive light sources for a variety of low-cost applications. Besides, the lasers should have competitive characteristics compared to devices based on high-quality inorganic resonators. Here, we report high performing all-solution-processed organic DFB lasers, consisting of water-processed photoresist layers with surface relief gratings located over the active films, whose emission properties can be finely tuned through resonator design. Their laser threshold and efficiency are simultaneously optimized by proper selection of residual resist thickness and grating depth, d. Lowest thresholds and largest efficiencies are obtained when there is no residual layer, while a trade-off between threshold and efficiency is found in relation to d, because both parameters decrease with decreasing d. This behaviour is successfully explained in terms of an overlap factor r, defined to quantify the interaction strength between the grating and the light emitted by the active film and traveling along it, via the evanescent field. It is found that optimal grating depths are in the range 100–130 nm (r ~ 0.5−0.4). Overall, this study provides comprehensive design rules towards an accurate control of the emission properties of the reported lasers.Financial support from Spanish Ministerio de Economía y Competitividad (MINECO) and the European FEDER funds through Grant MAT2015-66586-R

Seguimiento del Grado en Geología (Facultad de Ciencias, Universidad de Alicante, curso 2015-16)

La Facultad de Ciencias de la Universidad de Alicante ha constituido una red de trabajo formada por los profesores coordinadores de semestre del Grado en Geología, así como por los coordinadores responsables de la titulación. Los objetivos de esta red son: Asegurar la ejecución efectiva de las enseñanzas conforme al contenido del plan de estudios del título verificado; detectar posibles deficiencias en su implementación, proponiendo recomendaciones y sugerencias de mejora; y evidenciar los progresos en el desarrollo del Sistema de Garantía Interno de Calidad (SGIC) tanto en lo relativo a la revisión de la aplicación del plan de estudios como a la propuesta de acciones para mejorar su diseño en la implantación. El método de trabajo se basa en reuniones en las que los miembros de la red plantearán y debatirán los parámetros e indicadores de seguimiento de la red. Cada coordinador llevará a cabo una investigación individualizada del semestre del que es responsable en coordinación con los miembros de su comisión. Asimismo, se participará en la elaboración de los informes de autoevaluación del título