369 research outputs found
Anomalous dark current ideality factor (n > 2) in thin-film solar cells: The role of grain-boundary defects
No full textBy comparing simulated and measured dark I-V characteristics of CIGS cells, we investigate the low-voltage anomalous (> 2) ideality factor, and find that it can be explained by large donor trap concentrations at grain boundaries, and SRH recombination therein, with no need of complex models involving tunneling, coupled traps, etc. We studied 3 different samples, in all cases achieving excellent fit of the non-monotonic ideality factor. The illuminated cell performance also matches the experiments very well. The most important parameter determining value and voltage dependence of the anomalous ideality factor is the peak energy of the grain boundary donor distribution
Multidimensional mobile mapping and integrated approach for the digitalisation of underground transport infrastructure
No full textThe tunnel industry has started focusing on the maintenance and management challenges of an existing infrastructure. It is an urgent matter in industrialised countries, where the stakeholders’ attention is increasing at a fast pace considering the incidents and the disruptions caused by improper monitoring and maintenance. This paper presents an innovative methodology to survey and inspect existing railway tunnels through multi-dimensional mobile mapping systems. The proposed approach belongs to the digital strategies for infrastructure maintenance. An integrated multidimensional survey system (ARCHITA) allows for collecting information necessary for the diagnostics of a structure with non-destructive tests. Linear cameras, thermographic cameras, and ground-penetrating radars acquire data to be digitalised and manipulated in different IT environments. The results, in terms of the collected data on structural defects, allow for a new approach for the Management and Identification of the Risk for Existing Tunnels (MIRET). The innovative approach aims at a smart integration of information and models for the Facility Management of the transport system. The workflow for the digitalisation and diagnosis from mobile mapping data has been implemented on two 40km-long metro tunnels
On the temperature behavior of shunt-leakage currents in Cu(In,Ga)Se2 solar cells: The role of grain boundaries and rear Schottky contact
No full textBy comparing simulated and measured dark current-voltage (I-V) characteristics of CIGS cells at different temperatures, we investigate the temperature behavior of the shunt leakage current, and find that it can be explained by large donor trap concentrations at grain boundaries (GBs), and by a Schottky barrier at the backside contact where the GBs meets the anode metallization. We studied the I-V characteristics in the temperature range 280 K - 160 K achieving good fits of the measured I-V curves, especially for reverse bias and low forward bias, where the shunt leakage current dominates. The most important parameters determining the shunt leakage current value and its temperature dependence are the peak energy and density of the GB donor distribution, which control the inversion of GBs and the pinning of Fermi level at the anode/GB contact
A DIRECT MEASUREMENT OF THE ENERGY-SPECTRUM OF COSMIC-RAY MUONS IN THE MONT-BLANC UNDERGROUND LABORATORY
No full textIrreversible evolution of eumelanin redox states detected by an organic electrochemical transistor: en route to bioelectronics and biosensing
No full textOrg. electrochem. transistors (OECTs) are currently emerging as powerful tools for biosensing, bioelectronics and nanomedical applications owing to their ability to operate under liq. phase conditions optimally integrating electronic and biol. systems. Herein we disclose the unique potential of OECTs for detecting and investigating the elec. properties of insol. eumelanin biopolymers. Gate current measurements on fine aq. suspensions of a synthetic eumelanin sample from 5,6-dihydroxyindole (DHI) revealed a well detectable hysteretic response similar to that of the pure monomer in soln., with the formal concn. of the polymer as low as 10-6 M. Induction of the gate current would reflect electron transfer from solid eumelanin to the Pt-electrode sustained by redox active catechol/quinone components of the polymer. A gradual decrease in gate current and areas subtended by hysteretic loops were obsd. over 5 cycles both in the eumelanin- and DHI-based devices, suggesting evolution of the polymer from a far-from-the-equil. redox state toward a more stable electronic arrangement promoted by redox exchange with the gate electrode. OECTs are thus proposed as valuable tools for the efficient heterogeneous-phase sensing of eumelanins and to gauge their peculiar elec. and redox behavior
Defect structure and strain reduction of 3C-SiC/Si layers obtained with the use of buffer layer and methyltrichlorosilane addition
No full text3C-SiC layers were deposited on Si substrates by using a low temperature buffer layer and the addition of methyl trichloro silane (MTS) to the gas phase during the high temperature thick film growth. Several samples were grown by varying the deposition temperature and the MTS content in order to study how these parameters affect the layer quality and the lattice defects. All of the grown layers are single crystalline and epitaxial to the substrate. The formation of empty voids at the SiC/Si interface was successfully avoided. The surface of the layers grown with MTS addition was smoother and contained less residual strain. A 15 ?m thick 3C-SiC sample was grown with an optimized process in order to evaluate its residual strain and bow
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