Trap‐State Suppression and Improved Charge Transport in PbS Quantum Dot Solar Cells with Synergistic Mixed‐Ligand Treatments

The power conversion efficiency of colloidal PbS‐quantum‐dot (QD)‐based solar cells is significantly hampered by lower‐than‐expected open circuit voltage (V_OC). The V_OC deficit is considerably higher in QD‐based solar cells compared to other types of existing solar cells due to in‐gap trap‐induced bulk recombination of photogenerated carriers. Here, this study reports a ligand exchange procedure based on a mixture of zinc iodide and 3‐mercaptopropyonic acid to reduce the V_OC deficit without compromising the high current density. This layer‐by‐layer solid state ligand exchange treatment enhances the photovoltaic performance from 6.62 to 9.92% with a significant improvement in V_OC from 0.58 to 0.66 V. This study further employs optoelectronic characterization, X‐ray photoelectron spectroscopy, and photoluminescence spectroscopy to understand the origin of V_OC improvement. The mixed‐ligand treatment reduces the sub‐bandgap traps and significantly reduces bulk recombination in the devices.     

Distributed filtering over sensor networks for autonomous navigation of UAVs

The paper studies the problem of localization and autonomous navigation of a multi-UAV system with the use of Distributed Filtering methods (DF). It is considered that m UAV (helicopter) models are monitored by n different ground stations. The overall concept is that at each monitoring station a filter is used to track each UAV by fusing measurements which are provided by various UAV sensors, while by fusing the state estimates from the distributed local filters an aggregate state estimate for each UAV is obtained. In particular, the paper proposes first the extended information filter (EIF) and the unscented information filter (UIF) as possible approaches for fusing the state estimates provided by the local monitoring stations, under the assumption of Gaussian noises. The EIF and UIF estimated state vector is in turn used by a flatness-based controller that makes the UAV follow the desirable trajectory. Moreover, the distributed particle filter (DPF) is proposed for fusing the state estimates provided by the local monitoring stations (local filters). The motivation for using DPF is that it is well-suited to accommodate non-Gaussian measurements. The DPF estimated state vector is again used by the flatness-based controller to make each UAV follow a desirable flight path. Finally, a derivative-free implementation of the extended information filter (DEIF) is introduced aiming at obtaining more accurate estimates of the UAV state vector in real-time. The performance of the EIF, of the UIF, of the DPF and of the DEIF is evaluated through simulation experiments in the case of a 2-UAV model monitored and remotely navigated by two local stations.     

Modeling of fermentative hydrogen production from the bacterium Ruminococcus albus: Definition of metabolism and kinetics during growth on glucose

The aim of the present study was to describe the fermentative pathway of Ruminococcus albus during hydrogen production from glucose by a quantitative kinetic model, taking into account the interactions among the metabolic products during their generation. Proper mathematical expressions were developed in order to adequately describe the microbial growth and metabolism of R. albus. For the estimation of kinetics constants of the process, the experimental data from batch experiments were simulated using a simplified and modified version of Anaerobic Digestion Model 1 on Aquasim as a modeling platform. Subsequently the accuracy of the model was verified by simulating the performance of a CSTR in four different hydraulic retention times. Batch experiments with different initial substrate concentrations and different initial hydrogen partial pressures were carried out in order to calculate the growth kinetics of the microorganism and investigate the effect of hydrogen partial pressure to the production of metabolites. Microbial growth was described using Monod kinetics, taking into account the inhibition at lower pH values as well as the substrate inhibition, and the metabolites' profile was described using suitable kinetic expressions. Acetate and ethanol production were assumed to occur simultaneously, by direct sugar consumption and the H₂ final yield was reversely connected to the accumulation of ethanol. Formate was considered to be produced by direct sugar consumption, and subsequently to break down to H₂ and CO₂. The degradation rate of formate, and consequently hydrogen production were shown to be influenced by hydrogen partial pressure.     

Potential for biohydrogen and methane production from olive pulp.

The present study investigates the potential for thermophilic biohydrogen and methane production from olive pulp, which is the semi-solid residue coming from the two-phase processing of olives. It focussed on: a) production of methane from the raw olive pulp, b) anaerobic bio-production of hydrogen from the olive pulp, and c) subsequent anaerobic treatment of the hydrogen-effluent with the simultaneous production of methane. Both continuous and batch experiments were performed. The hydrogen potential of the olive pulp amounted to 1.6 mmole H2 per g TS. The methane potential of the raw olive pulp and hydrogen-effluent was as high as 19 mmole CH4 per g TS. This suggests that olive pulp is an ideal substrate for methane production and it shows that biohydrogen production can be very efficiently coupled with a subsequent step for methane production.     

Solid-State Thin-Film Broadband Short-Wave Infrared Light Emitters

Solid-state broadband light emitters in the visible have revolutionized today's lighting technology achieving compact footprints, flexible form factors, long lifetimes, and high energy saving, although their counterparts in the infrared are still in the development phase. To date, broadband emitters in the infrared have relied on phosphor-downconverted light emitters based on atomic optical transitions in transition metal or rare earth elements in the phosphor layer resulting in limited spectral bandwidths in the near-infrared and preventing their integration into electrically driven light-emitting diodes (LEDs). Herein, phosphor-converted LEDs based on engineered stacks of multi-bandgap colloidal quantum dots (CQDs) are reported as a novel class of broadband emitters covering a broad short-wave infrared (SWIR) spectrum from 1050–1650 nm with a full-width-half-maximum of 400 nm, delivering 14 mW of optical power with a quantum efficiency of 5.4% and power conversion efficiency of 13%. Leveraging the electrical conductivity of the CQD stacks, further, the first broadband SWIR-active LED is demonstrated, paving the way toward complementary metal–oxide–semiconductor integrated broadband emitters for on-chip spectrometers and low-cost volume manufacturing. SWIR spectroscopy is employed to illustrate the practical relevance of the emitters in food and material identification case studies.     

Ultrahigh Carrier Mobility Achieved in Photoresponsive Hybrid Perovskite Films via Coupling with Single‐Walled Carbon Nanotubes

Organolead trihalide perovskites have drawn substantial interest for photovoltaic and optoelectronic applications due to their remarkable physical properties and low processing cost. However, perovskite thin films suffer from low carrier mobility as a result of their structural imperfections such as grain boundaries and pinholes, limiting their device performance and application potential. Here we demonstrate a simple and straightforward synthetic strategy based on coupling perovskite films with embedded single‐walled carbon nanotubes. We are able to significantly enhance the hole and electron mobilities of the perovskite film to record‐high values of 595.3 and 108.7 cm² V^?1 s^?1, respectively. Such a synergistic effect can be harnessed to construct ambipolar phototransistors with an ultrahigh detectivity of 3.7 × 10¹⁴ Jones and a responsivity of 1 × 10⁴ A W^?1, on a par with the best devices available to date. The perovskite/carbon nanotube hybrids should provide a platform that is highly desirable for fields as diverse as optoelectronics, solar energy conversion, and molecular sensing.