RESUMEN
Transparent conductive electrodes (TCEs) fabricated onto flexible substrates are crucial parts of organic-light-emitting diodes (OLEDs), which are vastly utilized for display and lightning applications. Indium tin oxide (ITO), which is so far the most popular material for transparent and conductive electrodes, is found to be an unsuitable candidate for flexible devices mostly due to its brittleness. Here, we present a novel approach for the fabrication of transparent, conductive, and flexible electrodes for optoelectronic applications made of silver metal mesh by an ultraprecise deposition (UPD) method. The fabricated mesh exhibits an 80% (λ = 550 nm) optical transmittance and a sheet resistance of 11 Ω/sq. The Ag-mesh embedded into the polymer is implemented as an anode for a quantum-dot light-emitting diode (QLED) in order to assess its performance. The fabricated QLED is characterized by the maximum external quantum efficiency (EQE) of 2% and a current efficiency (CE) of 6 cd/A, reaching the maximum luminance (L) of 3200 cd/m2 at a current density of 100 mA/cm2. This method shows a fast and relatively simple approach to fabricate optoelectronic devices without the need for special treatment and sophisticated equipment.
RESUMEN
Additive manufacturing transforms the landscape of modern microelectronics. Recent years have witnessed significant progress in the fabrication of 2D planar structures and free-standing 3D architectures. In this work, we present a much-needed intermediary approach: we introduce the Ultra-Precise Deposition (UPD) technology, a versatile platform for material deposition at micrometer scale on complex substrates. The versality of this approach is related to three aspects: material to be deposited (conductive or insulating), shape of the printed structures (lines, dots, arbitrary shapes), as well as type and shape of the substrate (rigid, flexible, hydrophilic, hydrophobic, substrates with pre-existing features). The process is based on the direct, maskless deposition of high-viscosity materials using narrow printing nozzles with the internal diameter in the range from 0.5 to 10 µm. For conductive structures we developed highly concentrated non-Newtonian pastes based on silver, copper, or gold nanoparticles. In this case, the feature size of the printed structures is in the range from 1 to 10 µm and their electrical conductivity is up to 40% of the bulk value, which is the record conductivity for metallic structures printed with spatial resolution below 10 µm. This result is the effect of the synergy between the printing process itself, formulation of the paste, and the proper sintering of the printed structures. We demonstrate a pathway to print such fine structures on complex substrates. We argue that this versatile and stable process paves the way for a widespread use of additive manufacturing for microfabrication.
RESUMEN
In this paper, we show the carbonization of binary composites consisting of graphene nanoplatelets and melamine (GNP/MM), multi-walled carbon nanotubes and melamine (CNT/MM) and trinary composites containing GNP, CNT, and MM. Additionally, the manuscript presents results on the influence of structural factors for the electrochemical performance of carbon composites on their catalytic activity. This study contributes to the wide search and design of novel hybrid carbon composites for electrochemical applications. We demonstrate that intensive nitrogen atom insertion is not the governing factor since hybrid system modifications and porous structure sometimes play a more crucial role in the tailoring of electrochemical properties of the carbon hybrids seen as a noble metal-free alternative to traditional electrode materials. Additionally, HRTEM and Raman spectra study allowed for the evaluation of the quality of the obtained hybrid materials.
RESUMEN
This work demonstrates the influence of high-quality protection layers on Si-Cu2O micropillar arrays created by pulsed laser deposition (PLD), with the goal to overcome photodegradation and achieve long-term operation during photoelectrochemical (PEC) water splitting. Sequentially, we assessed planar and micropillar device designs with various design parameters and their influence on PEC hydrogen evolution reaction. On the planar device substrates, a Cu2O film thickness of 600 nm and a Cu2O/CuO heterojunction layer with a 5:1 thickness ratio between Cu2O to CuO were found to be optimal. The planar Si/Cu2O/CuO heterostructure showed a higher PV performance (Jsc = 20 mA/cm2) as compared to the planar Si/Cu2O device, but micropillar devices did not show this improvement. Multifunctional overlayers of ZnO (25 nm) and TiO2 (100 nm) were employed by PLD on Si/Cu2O planar and micropillar arrays to provide a hole-selective passivation layer that acts against photocorrosion. A micropillar Si/ITO-Au/Cu2O/ZnO/TiO2/Pt stack was compared to a planar device. Under optimized conditions, the Si/Cu2O photocathode with Pt as a HER catalyst displayed a photocurrent of 7.5 mA cm-2 at 0 V vs RHE and an onset potential of 0.85 V vs RHE, with a stable operation for 75 h.
RESUMEN
Here, we present a seeded Knoevenagel dispersion polymerization to generate hybrid particles with a conjugated polymer shell on inorganic silica cores. This seeded dispersion polymerization facilitates the generation of core-shell particles, which exhibit whispering gallery mode lasing. The lasing threshold decreases while the spectral range of emission increases with increasing shell thickness. This novel seeded Knoevenagel dispersion polymerization opens up a facile and metal free pathway towards single particle conjugated polymer lasers on the micrometer scale.