This work shows a comparative study of organic light emitting diodes based on four different europium complexes with the general formula, Eu(CLs)3bipyridine, where the central ligands are DBM [tris(dibenzoylmethane)], TTA [tris(1-(2-thieneyl)-4,4,4-trifluoro-1,3-butanedione)], NTA [tris(1-(2-naphthoyl)-3,3,3-trifluoroacetone)] and BTA [tris(1-(2-benzoyl)-3,3,3-trifluoroacetone)]. All devices have a driving voltage of 14–16 V, a very low electrical current at normal operation (less than 1 mA) and a good Wall Plug Efficiency (up to near 10−3%). The most suitable central ligand was found to be DBM, with an optical power up to 200 nW (at 612 nm). The BTA exhibits the lowest stability under high applied voltages. The other central ligands have similar results among them. The electroluminescence spectra clearly show the europium ion transitions (with a strong 5D0 → 7F2 line) with a CIE color coordinate around (0.56, 0.34).

In this work, a ruthenium hexafluorophosphate complex, [Ru(bpy)3](PF6)2 in poly(methylmethacrylate) (PMMA) was employed to build a single layer light electrochemical cell on indium tin oxide polyester flexible substrate. The electroluminescence spectrum features a relatively broad band peaked near 625 nm, with CIE (x, y) color coordinates of (0.61, 0.39). The driving voltage is only 3 V, and for the maximum electrical current of 10 mA the brightness reaches 1 cd/m2. Regarding the useful application of the device, its opto-electrical behavior under mechanical strain was studied considering the central curvature. In these situations, both electrical characterization in DC mode and luminance were analyzed.

This work shows the luminescence properties of a rare-earth organic complex, the Tb(ACAC)3phen. The results show the 5D4 -> 7F3,4,5,6 transitions with no influence of any ligand emission. The photoluminescence excitation spectrum is tentatively interpreted by the ligands absorption. An OLED was made by thermal evaporation (total thickness of 1200 Å) using TPD and Alq3 as hole and electron transport layers, respectively. The light emission reproduces the photoluminescence spectrum of the terbium complex at room temperature, with CIE (x,y) color coordinates of (0.28, 0.55). No presence of any bands from the ligands was observed. The potential use of this compound in efficient devices is discussed.

The luminous efficiency of organic light-emitting diodes based on poly(N-vinylcarbazole), PVK, was improved by adding fac-[ClRe(CO)3(bpy)], bpy = 2,2′-bipyridine, to PVK host. Emissive layers with various Re(I) complex/host ratio were employed and optoelectronic properties were compared with the single PVK device. The single PVK device exhibits a characteristic electroluminescence with blue emission, λmax 420 nm, assigned to the PVK excimer. On the other hand, the intense and broad band at λmax 580 nm of the Re(I) complex/PVK OLEDs is ascribed to the metal-to-ligand charge transfer excited state emission of fac-[ClRe(CO)3(bpy)]. At 30 V, the device luminous efficiency increased from 16 mcd/A for the single PVK device to 211 mcd/A for the 11% (w/w) Re(I) complex/PVK OLED, in which fac-[ClRe(CO)3(bpy)] acts as an electron-trap in PVK films. The device current is space-charge limited and exhibits typical emissive layer thickness dependence

RESUMEN: Los avances en la detección de defectos en módulos fotovoltaicos por luminiscencia se están viendo demorados por la necesidad que las técnicas de inspección actuales tienen de actuar sobre los contactos eléctricos y retirar los paneles de su estado de funcionamiento. En el presente trabajo se introduce un sistema que vence esta limitación, pudiendo tomar imágenes de luminiscencia sobre módulos solares en funcionamiento. Dicho sistema se pone a prueba mediante la implementación de un primer prototipo funcional, con el que se toman imágenes de un string de células completo para poder compararlas con las obtenidas utilizando las técnicas de inspección actuales, determinando así sus similitudes y diferencias, y corroborando la validez del método propuesto.

We survey the current state of models for electronic processes in conducting polymer devices, especially light-emitting diodes. We pay special attention to several processes that have been somewhat neglected in the previous literature: charge injection from electrodes into a polymer sample, mobility of charge-or energy-carrying defects within a single molecule and (more briefly) transfer of carriers between molecules and the interaction between the charge transport and the mesostructure of the polymer. Within all these areas substantial. progress has been made in recent years in elucidating the important physics, but further progress is needed to make quantitative contact with experiment.

In this work, the main characteristics of a Gas Proportional Scintillation Counter (GPSC) filled with pure krypton at atmospheric pressure are investigated. Two different GPSCs have been assembled, one instrumented with a Large Area Avalanche Photodiode (LAAPD) and the other instrumented with a vacuum Photomultiplier Tube (PMT) having a magnesium fluoride window. Both photosensors are sensitive to the second-continuum emission, a narrow band centred at 147 nm with a ~12 nm FWHM, which constitutes the main emission in Kr for pressures above several tens of mbar.In particular, the energy resolution achieved at 5.9 keV is studied as a function of the electric field imposed on drifting electrons and as a function of the x-ray energy in the 6-50 keV range. An energy resolution between 10 and 11% (FWHM) was obtained for 5.9 keV, while for energies above ~30 keV the energy resolution obtained in the GPSC-PMT is around 6.5%. These energy resolutions are somewhat higher than those achieved in similar Xe-based GPSC instrumented with a quartz window PMT, 8% at 5.9 keV and ~5.5% for x-ray energies above 30 keV.In addition to the characterization of the GPSCs, this work studied several characteristic properties of krypton. These include the Fano factor F in response to x-ray interactions and the Electroluminescence (EL) and ionization thresholds related to free electrons drifting under an external electric field. A value of 6.8 +- 0.6 eV was experimentally estimated for Fw, being w the mean energy necessary to create a free electron in Kr by x-ray interaction, which leads to a value of F = 0.28 +- 0.03 for the Fano factor, considering w(Kr) = 24.2 eV. The EL and ionization thresholds obtained from the whole experimental data were 0.71 +- 0.04 and 3.29 +- 0.11 kV/cm/bar, respectively. These values are in good agreement with those obtained by the state-of-the-art simulations.In the GPSC instrumented with the LAAPD it is possible to determine the EL scintillation yield, Y, i.e. the number of EL photons produced per drifting electron per path unit, resorting to direct interactions of 5.9 keV photons in the LAAPD (silicon) to calibrate the LAAPD pulse output in number of electron-hole pairs produced in its sensitive volume. Knowing the LAAPD Quantum Efficiency (QE) at 147 nm is possible to determine the number of EL photons that hit the LAAPD sensitive area for a given LAAPD pulse resulting from the EL burst. As expected, the experimental results of the reduced EL Yield, Y/p, as a function of the reduced electric field, E/p, being p the gas pressure, are well described by a linear fit, between the EL and ionization thresholds. Considering the experimental data obtained from both PMT- and LAAPD-based GPSCs the reduced EL Yield is best described by Y/p = (117 +- 4)E/p + (-82 +- 6) (photons/electron/cm/bar). The amplification parameter, i.e. the slope of the linear fit, 117 +- 4 photons/electron/V, is also in good agreement with that obtained from Garfield++ simulations. It was assumed that any emission on the so-called third-continuum is negligible: its fraction will be small when compared to the overall EL emission and it will be emitted in the UV or the near-UV ranges where the LAAPD quantum efficiency is much lower than that at 147 nm.Using the PMT-GPSC prototype, the primary scintillation yield of Kr in response to interactions of x-rays with different energies was also investigated. We could confirm recent studies on primary scintillation in a PMT-GPSC with pure xenon gas filling: the primary scintillation yield does not depend on the radiation energy. The mean energy required to produce one S1 photon, w(sc), was found to be w(sc) = 64 +- 4 (stat.) +- 8 (syst.) eV in gaseous Kr at 1.1 bar. To the best of our knowledge, there are no other results in the literature that we can compare with.The triplet decay time of krypton excimers was also measured at 1.1 bar and room temperature, using alpha-induced scintillation, yielding a value of 0.329 +- 0.001 microseconds, consistent with established literature values for the krypton second continuum.

There is a growing interest for the next-generation of soft-matter optoelectronic devices that can bend, stretch and deform. From bendable mobile phones, or displays, to electronic skin and electronic textiles that can be wrapped around any object to display information. As a step toward this goal, this work studies materials and methods for fabrication of thin-film stretchable electroluminescent devices, using liquid metal based stretchable composites.At the core of this work is the study of new fabrication strategies that integrate conductive inks, liquid metal, and processing methods to address the limitations of traditional designs. Through a series of prototypes, this research identifies the key factors that influence device fabrication and performance. The effect of dielectric thickness on light emission was examined, showing how it can be tuned for improved performance and localized emission. The deposition of the emissive layer was also investigated. In addition, as a step toward higher-resolution EL displays, it was studied fabrication of multi-layer stretchable circuits. This resulted in the development of a single-step VIA filling method, taking advantage of the natural affinity between liquid metal and silver. This approach was motivated by previous prototypes, where manual VIA filling with conductive ink proved feasible but was restricted by poor scalability and operator dependence. The aim was to create electroluminescent devices with VIA-based pixels, designed for scalable, reliable, and stretchable interconnections using liquid metal and printable silver composites.The study also follows the evolution of VIA filling, demonstrating that polymer encapsulation is essential to preserving LM bubble morphology and maintaining conductivity under tensile strain. The results highlight the delicate interplay between structure, conductivity, and light emission, providing insights into pathways for more resilient and versatile devices.This research establishes a step toward scalable fabrication of multi-layer stretchable circuits and EL devices with VIA pixels. The findings provide significant insights into LM–ink integration, laser-assisted VIA formation, and encapsulation strategies, pointing toward future applications in interactive displays and soft sensing systems.