In this paper, we compare four different methods to estimate nanoparticle diameters from optical absorption measurements, using transmission electron microscopy (TEM) images as a reference for the nanoparticle size. Three solutions of colloidal nanoparticles coated with thiophenol with different diameters were synthesized by thiolate decomposition. The nanoparticle sizes were controlled by the addition of a certain volume of a 1% sulphur solution in toluene. TEM measurements showed that the average diameter for each type of these nanoparticles was 2.8 nm, 3.2 nm, and 4.0 nm. The methods studied for the calculation of the nanoparticles diameter were: The Brus model, the hyperbolic band model (HBM), the Henglein model, and the Yu equation. We evaluated the importance of a good knowledge of the nanoparticle bandgap energy, and the nature of electronic transitions in the semiconductor. We studied the effects that small variations in the electron and hole effective mass values produced in the Brus equation and in the HBM model for CdS, PbS, and ZnS nanoparticles. Finally, a comparison was performed between the data provided by these models and the experimental results obtained with TEM images. In conclusion, we observed that the best approximation to the experimental results with TEM images was the Brus equation. However, when the bandgap energy was close to the bulk bandgap energy, the theoretical models did not adjust correctly to the size measured from the TEM images.

Immiscibility between dimethyl sulfoxide (DMSO) and polar solvents used for poly(N-vinylcarbazole) (PVK) solutions, leads to failed light-emitting diodes when colloidal cadmium sulfide (CdS) nanoparticles capped with thiophenol are incorporated to their active layer. To prevent this, a heat treatment is applied to the CdS nanoparticles in order to evaporate DMSO solvent. After evaporation most of the nanoparticles increased their size, and some of them show hexagonal crystalline structure instead of the original cubic zinc-blende observed in colloidal pre-treated nanoparticles. Nevertheless, enhanced electronic properties are measured in light-emitting devices when DMSO-free nanoparticles are embedded in the poly(N-vinylcarbazole) active layer. Light emission from these hybrid devices comprises the whole visible range of wavelengths as searched for white LEDs. Moreover, electroluminescence from both types of CdS nanoparticles (smaller cubic and bigger hexagonal) has been discriminated and interpreted through Gaussian deconvolution.

In this study, poly(9-vinylcarbazole) (PVK)-based LEDs doped with reduced graphene oxide (rGO) and cadmium sulphide (CdS) nanocrystals were fabricated by spin-coating. The hybrid LED structure was a layer sequence of glass/indium tin oxide (ITO)/PEDOT:PSS|rGO/PVK/Al. rGO was included in the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) layer due to its energy bands being close to PEDOT:PSS bands, and the possibility of using water for dispersing both polymer and flakes. Optical properties such as photoluminescence and UV-Vis absorption were not affected by the addition of rGO to the PEDOT:PSS solution. However, PVK-based LEDs with rGO showed increased current density compared to those without rGO in the hole transporting layer. Higher electroluminescence intensities were observed for rGO-enriched LEDs, although the shape of the spectrum was not modified. LEDs including CdS nanocrystals in the poly(9-vinylcarbazole) emissive layer did not show such dependence on the rGO presence. Though the addition of rGO to PEDOT:PSS still produces a slightly higher current density in CdS doped LEDs, this growth is no longer proportional to the rGO load.

Deep levels have been characterized in Si-doped and undoped InAlAs layers lattice matched to InP. At ambient pressure and low temperature, the Schottky junction capacitance shows a small persistent photocapacitance effect, related to photoionization thresholds at 0.6 and 1.1 eV. Deep-level transient spectroscopy spectra show a dominant, low-density electron trap at around 320 K, with an emission energy very dependent on the bias conditions and the hydrostatic pressure (0.5 to 0.9 eV). This is attributed to an interaction of a high density of interface states with the trap emission process. Under hydrostatic pressure, neither the PPC per cent nor the DLTS spectra shape changes. Photoluminescence spectra in both Si-doped and undoped InAlAs layers show two weak peaks at 0.80 and 0.95 eV, that the authors suggest are due to a native defect involving an As antisite. They conclude that the detected traps have no relation with the DX centres.

Over the past few decades, the incipient growth of technology applications sustained by electronics has contributed to the adaption of learning programs in many engineering degrees at university, fostering the presence of electronics subjects. This highlights the paramount importance of improving the teaching of electronics, especially in the first years of Bachelor’s degrees in engineering. However, despite the fact that the teaching programs have been periodically renewed with more practical sessions, the students’ outcomes are still noticeably low. So far, results only confirm improvements in the students’ performance in the resolution of electronic circuits. Nonetheless, this is generally subject to the application of repetitive circuit resolution models, to the detriment of the real and active understanding of electronic principles. In this context, this study assesses the actual efficacy of different ICT (Information, Communication and Technology) resources, introduced into an electronics course, taught in an engineering Bachelor’s degree, within the Spanish official university system. These resources have been sequentially introduced during five consecutive years. We have conducted a statistical analysis to infer whether all the resources are equally relevant for the achievement of the students or not. In addition, we have designed a survey to measure the perceived improvement in the understanding of concepts, acquired competences, and reported satisfaction and attitude towards the use of specific resources during the program. Amongst others, LMS (Learning Management System) support, online PBL (Problem-Based Learning) activities, and CSA (Circuit Simulation Applets) have been considered. Overall, the designed learning program has been intended to provide students with long-term references to enrich their resources’ background regarding electronics.

This paper presents the electrical characteristics of solution-processed organic photodetectors based on poly(3-hexylthiophene-2,5-diyl) semiconducting polymer layers deposited by spin-coating on interdigitated metal electrodes. Four different electrode shapes have been used for this study in order to appraise the optimum electrode geometry. The measurement of the resistance as a function of the temperature reveals a transition from negative to positive temperature coefficient material around 80 °C for the polymer layers. Besides, slow reversible changes in the photodetectors conductivity were observed when moved from vacuum to the air and under illumination with a xenon lamp, which can be explained by the formation of charge transfer complexes with molecular oxygen and the polymer. The photogenerated current-light power ratio was found to be approximately linear in the 200 to 550 mW/cm² range.