High Open Circuit Voltage Solar Cells based on bright mixed-halide CsPbBrI2 Perovskite Nanocrystals Synthesized in Ambient Air Conditions

Lead halide perovskite nanocrystals (NCs) are currently emerging as one of the most interesting solution processed semiconductors since they possess high photoluminescence quantum yield (PLQY), and colour tunability through anion exchange reactions or quantum confinement. Here, we show efficient solar cells based on mixed halide (CsPbBrI2) NCs obtained via anion exchange reactions in ambient conditions. We performed anion exchange reactions in concentrated NC solutions with I-, thus inducing a PL red-shift up to 676 nm, and obtaining a high PLQY in film (65%). Solar cell devices operating in the wavelength range 350-660 nm were fabricated in air with two different deposition methods. The solar cells display a photo-conversion efficiency of 5.3% and open circuit voltage (Voc) up to 1.31V, among the highest reported for perovskite based solar cells with band gap below 2eV, clearly demonstrating the potential of this material.Peer ReviewedPostprint (author's final draft

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 (VOC). The VOC 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 VOC 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 VOC 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 VOC improvement. The mixed‐ligand treatment reduces the sub‐bandgap traps and significantly reduces bulk recombination in the devices.Peer ReviewedPostprint (author's final draft

Broadband amplified spontaneous emission and random lasing from wurtzite CdSe/CdS 'giant-shell' nanocrystals

Colloidal nanocrystals (NCs) are attractive materials for light-emitting applications thanks to their flexible synthesis, size-dependent properties, and bright emission. Yet, colloidal NCs still present a narrow gain band (full-width half maximum around 10 nm), which limits their application to single-color lasers. Widening of the gain band by specifically engineered NCs can further improve the prospect of this class of materials toward the fabrication of solution-processed white-emitting or color-tunable lasers. Here, we report broadband amplified spontaneous emission (ASE) from wurtzite CdSe/CdS "giant-shell" nanocrystals (g-NCs) with an unprecedented large core up to 7.5 nm in diameter that were synthesized through a continuous injection route. The combination of large core and shell enables ASE from different CdSe optical transitions as well as from the CdS. Importantly, thin films of g-NCs with a large CdSe core (7.5 and 5.1 nm in diameter) show ASE at different colors with a similar threshold, indicating that light emission amplification can be achieved from different optical transitions simultaneously. Tuning of the core diameter allows obtaining ASE in a wide spectral range, and blending of g-NCs with different core sizes gives rise to a continuous amplified spontaneous emission band from green to red (510 to 650 nm). Drop-cast films of CdSe/CdS g-NCs demonstrate simultaneous dual-color random lasing under nanosecond-pulsed excitation

Corticobasal syndrome: neuroimaging and neurophysiological advances

Corticobasal degeneration (CBD) is a neurodegenerative condition characterized by 4R-tau protein deposition in several brain regions that clinically manifests itself as a heterogeneous atypical parkinsonism typically expressing in the adulthood. The prototypical clinical phenotype of CBD is corticobasal syndrome (CBS). Important insights into the pathophysiological mechanisms underlying motor and higher cortical symptoms in CBS have been gained by using advanced neuroimaging and neurophysiological techniques. Structural and functional neuroimaging studies often showed asymmetric cortical and subcortical abnormalities, mainly involving perirolandic and parietal regions and basal ganglia structures. Neurophysiological investigations including electroencephalography and somatosensory evoked potentials provided useful information on the origin of myoclonus and on cortical sensory loss. Transcranial magnetic stimulation demonstrated heterogeneous and asymmetric changes in the excitability and plasticity of primary motor cortex and abnormal hemispheric connectivity. Neuroimaging and neurophysiological abnormalities in multiple brain areas reflect the asymmetric neurodegeneration, leading to the asymmetric motor and higher cortical symptoms in CBS. This article is protected by copyright. All rights reserved

Thermodynamic simulation of atmospheric DLI-CVD processes for the growth of chromium-based hard coatings using bis(benzene)chromium as molecular source

Direct liquid injection (DLI) is a new technology particularly convenient for feeding CVD reactors with low volatility molecular precursors. Thus DLI-CVD can operate under atmospheric pressure and is a promising process for industrial applications requiring high precursor flow rates such as continuous deposition. In order to help the experimenter, a thermodynamic approach is particularly suitable for determining the chemistry of the process, i.e. the influence of the main growth parameters such as temperature, total pressure and initial gas phase composition on the nature of the deposited phases. A choice of the most explicit representations of the thermodynamic modelling describing the great trends resulting from the variation of experimental parameters is presented. Thermodynamic calculations in the Cr–C–H, Cr–N–C–H and Cr–C–Cl–H chemical systems were made to predict the atmospheric CVD growth of carbides, nitrides andmetal chromium coatings, respectively. Bis(benzene)chromium (BBC) was used as metalorganic precursor and the calculations simulated respectively the reactive gas phase mixtures BBC/solvent, BBC/NH3/solvent and BBC/C6Cl6/solvent. Even if a satisfactory agreement was found between experimental and theoretical tendencies, the deposition of metastable phases reveals that kinetics can play amajor role in such processes. Based on these results, chromium carbides, nitrides and metal coatings have been successfully deposited by DLI-CVD under atmospheric pressure either as single phased or nanostructured multilayer hard coatings

Link optimization considerations for 5G and beyond wireless communications

L'abstract è presente nell'allegato / the abstract is in the attachmen

Multirate 5G Downlink Performance Comparison for f-OFDM and w-OFDM Schemes with Different Numerologies

One of the main open problems for next generation wireless networks, is to find the new OFDM-based waveform to be used in 5G. The new modulation scheme must primarily be able to achieve higher spectral efficiency than its predecessor. The main 3GPP's candidate is a new version of OFDM, called Filtered Orthogonal Frequency-Division Multiplexing (f-OFDM), which is similar to OFDM but with additional filtering in order to reduce Out-Of-Band (OOB) emissions and to obtain a better spectral-localization. Another option is windowed-OFDM (w-OFDM), which is basically a classical OFDM scheme where each symbol is windowed and overlapped in the time domain. In this paper we compare classic OFDM signals using Cyclic Prefix (CP-OFDM) with f-OFDM and w-OFDM, each one with multiple parametric options and numerologies. A multirate transmitter simultaneously operating with multiple numerologies is considered, where the transmitted sub-bands must be up-sampled and interpolated in order to generate the composite numerical signal fed to the Digital to Analog Converter (DAC). Finally, we discuss advantages and disadvantages of the various schemes.Comment: Paper accepted for ISNCC 201

Pure-Past Linear Temporal and Dynamic Logic on Finite Traces

LTLf and LDLf are well-known logics on finite traces. We review PLTLf and PLDLf, their pure- past versions. These are interpreted backward from the end of the trace towards the beginning. Because of this, we can exploit a foundational result on reverse languages to get an exponential improvement, wrt LTLf /LDLf, in computing the corresponding DFA. This exponential improvement is reflected in several forms sequential decision making involving temporal specifications, such as planning and decision problems in non-deterministic and non-Markovian domains. Interestingly, PLTLf (resp. PLDLf ) has the same expressive power as LTLf (resp. LDLf ), but transforming a PLTLf (resp. PLDLf ) formula into its equivalent in LTLf (resp. LDLf ) is quite expensive. Hence, to take advantage of the exponential improvement, properties of interest must be directly expressed in PLTLf /PLTLf