Visible light communication systems can be used in a wide variety of applications, from driving to home automation. The use of wearables can increase the potential applications in indoor systems to send and receive specific and customized information. We have designed and developed a fully organic and flexible Visible Light Communication system using a flexible OLED, a flexible P3HT:PCBM-based organic photodiode (OPD) and flexible PCBs for the emitter and receiver conditioning circuits. We have fabricated and characterized the I-V curve, modulation response and impedance of the flexible OPD. As emitter we have used a commercial flexible organic luminaire with dimensions 99 × 99 × 0.88 mm, and we have characterized its modulation response. All the devices show frequency responses that allow operation over 40 kHz, thus enabling the transmission of high quality audio. Finally, we integrated the emitter and receiver components and its electronic drivers, to build an all-organic flexible VLC system capable of transmitting an audio file in real-time, as a proof of concept of the indoor capabilities of such a system.

Halide perovskites (HPs) are promising materials for memristor devices because of their unique characteristics. In this study, nonvolatile resistive switching memory devices based on thick MAPbI₃ perovskite (800 nm) films with structure FTO/MAPbI₃/polymethyl methacrylate (PMMA)/Ag are presented. Reproducible and reliable bipolar switching characteristics are demonstrated with an ultra‐low operating voltage (−0.1 V), high ON/OFF ratio (10⁶), endurance (>2 × 10³ times) and a record retention time (>10⁵ s). The I–V curve of the first cycle exhibits self‐formed conductive filaments. These are attributed to the presence of metallic Pb resulting from an excess of PbI₂ in the perovskite film. The subsequent activation process involves the formation of conductive filaments, consisting of either iodide vacancies or migrated charged metals. Numerical simulations are then carried out to understand the nature of these conductive filaments and the role of the internal electric field in the migration of iodide ions, iodide vacancies, and Ag cations. Finally, an exhaustive model is proposed that explains the set and reset processes governing the first voltage cycle and the steady state, at different voltage ranges. In summary, this work offers a novel and thorough perspective of the complete resistive switching (RS) behavior in a MAPbI₃/buffer/Ag memristor, supported by numerical simulations.

This article presents a full course for autonomous aerial robotics inside the RoboticsAcademy framework. This “drone programming” course is open-access and ready-to-use for any teacher/student to teach/learn drone programming with it for free. The students may program diverse drones on their computers without a physical presence in this course. Unmanned aerial vehicles (UAV) applications are essentially practical, as their intelligence resides in the software part. Therefore, the proposed course emphasizes drone programming through practical learning. It comprises a collection of exercises resembling drone applications in real life, such as following a road, visual landing, and people search and rescue, including their corresponding background theory. The course has been successfully taught for five years to students from several university engineering degrees. Some exercises from the course have also been validated in three aerial robotics competitions, including an international one. RoboticsAcademy is also briefly presented in the paper. It is an open framework for distance robotics learning in engineering degrees. It has been designed as a practical complement to the typical online videos of massive open online courses (MOOCs). Its educational contents are built upon robot operating system (ROS) middleware (de facto standard in robot programming), the powerful 3D Gazebo simulator, and the widely used Python programming language. Additionally, RoboticsAcademy is a suitable tool for gamified learning and online robotics competitions, as it includes several competitive exercises and automatic assessment tools.

The evolution of Si bulk minority carrier lifetime during the heteroepitaxial growth of III–V on Si multijunction solar cell structures via metal‐organic chemical vapor deposition (MOCVD) has been analyzed. In particular, the impact on Si lifetime resulting from the four distinct phases within the overall MOCVD‐based III–V/Si growth process were studied: (1) the Si homoepitaxial emitter/cap layer; (2) GaP heteroepitaxial nucleation; (3) bulk GaP film growth; and (4) thick GaAs_yP_1‐y compositionally graded metamorphic buffer growth. During Phase 1 (Si homoepitaxy), an approximately two order of magnitude reduction in the Si minority carrier lifetime was observed, from about 450 to ≤1 µs. However, following the GaP nucleation (Phase 2) and thicker film (Phase 3) growths, the lifetime was found to increase by about an order of magnitude. The thick GaAs_yP_1‐y graded buffer was then found to provide further recovery back to around the initial starting value. The most likely general mechanism behind the observed lifetime evolution is as follows: lifetime degradation during Si homoepitaxy because of the formation of thermally induced defects within the Si bulk, with subsequent lifetime recovery due to passivation by fast‐diffusing atomic hydrogen coming from precursor pyrolysis, especially the group‐V hydrides (PH₃, AsH₃), during the III–V growth. These results indicate that the MOCVD growth methodology used to create these target III–V/Si solar cell structures has a substantial and dynamic impact on the minority carrier lifetime within the Si substrate. Copyright © 2015 John Wiley & Sons, Ltd.