Admittance spectroscopy of charge traps of FET based on nanotubes

Investigation of electrical properties of FET based on polymer wrapped nanotubes, namely charge carrier transport and trap appear mechanisms. Model of carrier transport in the device was performed. Local traps states activation energies were obtained

An approximation solvability method for nonlocal differential problems in Hilbert spaces

A new approach is developed for the solvability of nonlocal problems in Hilbert spaces associated to nonlinear differential equations. It is based on a joint combination of the degree theory with the approximation solvability method and the bounding functions technique. No compactness or condensivity condition on the nonlinearities is assumed. Some applications of the abstract result to the study of nonlocal problems for integrodifferential equations and systems of integro-differential equations are then showed. A generalization of the result by using nonsmooth bounding functions is given

Sensitive triplet exciton detection in polyfluorene using Pd-coordinated porphyrin

We developed a sensitive spectroscopic method to probe triplet concentration in thin films of polyfluorene (PF) at room temperature. The energy of photoexcited triplet excitons is transferred to the guest metal–organic complex, meso-tetratolylporphyrin-Pd (PdTPP), and detected as phosphorescent emission. The phosphorescence intensity of PdTPP–PF blends is proportional to the independently measured triplet concentration using photoinduced absorption experiments. The high sensitivity of this method allows room temperature detection of triplet excitons in spin-coated polymer films as thin as 10 nm. We found that the triplet lifetime is independent of PdTPP concentration and therefore this method is nearly non-perturbing for the triplet population.

Scalable fabrication of efficient p-n junction lead sulfide quantum dot solar cells

Nowadays, the best lead sulfide (PbS) colloidal quantum dot (CQD) solar cells are primarily demonstrated in the n-p structure, while the p-n structure is significantly less developed. This technological gap between the n-p and p-n structures is much more distinct than in cases of other solution-processable photovoltaic technologies like perovskites and polymers. Here, we propose a scalable fabrication strategy for efficient PbS QD solar cells with p-n structure. An industrially suited blade-coating technique has been used to deposit both n-type and p-type QD layers. The obtained solar cells demonstrated power conversion efficiency of 9%, thus, commensurate to the record device efficiency with this architecture fabricated with a non-scalable technique. The availability of both p-n and n-p structures fabricated from scalable methods may promote the future integration of the PbS QDs into tandem devices together with other solution-processable materials to exploit the most prominent benefits of the PbS QDs, such as infrared absorption.</p

Simulations of the polarized radio sky and predictions on the confusion limit in polarization for future radio surveys

Numerical simulations offer the unique possibility to forecast the results of surveys and targeted observations that will be performed with next generation instruments like the Square Kilometre Array. In this paper, we investigate for the first time how future radio surveys in polarization will be affected by confusion noise. To do this, we produce 1.4 GHz simulated full-Stokes images of the extra-galactic sky by modelling various discrete radio sources populations. The results of our modelling are compared to data in the literature to check the reliability of our procedure. We also estimate the number of polarized sources detectable by future surveys. Finally, from the simulated images we evaluate the confusion limits in I, Q, and U Stokes parameters, giving analytical formulas of their behaviour as a function of the angular resolution.Comment: 9 pages, 8 figure

Simulations of the polarized radio sky and predictions on the confusion limit in polarization for future radio surveys

Numerical simulations offer the unique possibility to forecast the results of surveys and targeted observations that will be performed with next generation instruments like the Square Kilometre Array. In this paper, we investigate for the first time how future radio surveys in polarization will be affected by confusion noise. To do this, we produce 1.4 GHz simulated full-Stokes images of the extra-galactic sky by modelling various discrete radio sources populations. The results of our modelling are compared to data in the literature to check the reliability of our procedure. We also estimate the number of polarized sources detectable by future surveys. Finally, from the simulated images we evaluate the confusion limits in I, Q, and U Stokes parameters, giving analytical formulas of their behaviour as a function of the angular resolution

Double Gate PbS Quantum Dot Field-Effect Transistors for Tuneable Electrical Characteristics

In this work colloidal quantum dots double gate transistors are introduced. A high-k (k = 43) relaxor ferroelectric polymer is used as a dielectric material for the top gate in a device where the other gate is fabricated from SiO2. The device in double gate configuration is characterized by reduced hysteresis in the transfer curves measured by separately sweeping the voltage of the SiO2 and of the polymer gate. Gating with the relaxor polymer leads to mobility values of μe = 1.1 cm2 V−1s−1 and μh = 6 × 10−3 cm2 V−1s−1 that exceed those extracted from the SiO2 gating: μe = 0.5 cm2 V−1s−1 and μh = 2 × 10−3 cm2 V−1s−1. Measurements under double gating conditions prove that the device works in a single channel mode that is delocalized over the whole film thickness. Double gating allows for shifting the threshold voltage into a desired position and also allows increasing the on-current of the devices

Opto-electronics of PbS quantum dot and narrow bandgap polymer blends

Here we report on the interaction between the narrow bandgap polymer [2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta-[2,1-b;3,4-b]dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (PCPDTBT) and lead sulphide (PbS) colloidal quantum dots (CQDs) upon photoexcitation. We show that the presence of both materials in a blend leads to a significant reduction of photoluminescence (PL) lifetime of the polymer. This observation is attributed, supported by transient absorption (TA) data, to an efficient electron transfer towards the QDs for excitons generated on the polymer. Furthermore, the ligand capping the QD surface exhibits a great impact on the dynamics of the PL, with the long-chain oleic acid (OA) largely suppressing any kind of interaction. By means of external quantum efficiency (EQE) measurements we find evidence that both components give rise to a contribution to the photocurrent, making this an interesting blend for future applications in hybrid organic-inorganic solar cells.</p

Bit-Vector Model Counting using Statistical Estimation

Approximate model counting for bit-vector SMT formulas (generalizing \#SAT) has many applications such as probabilistic inference and quantitative information-flow security, but it is computationally difficult. Adding random parity constraints (XOR streamlining) and then checking satisfiability is an effective approximation technique, but it requires a prior hypothesis about the model count to produce useful results. We propose an approach inspired by statistical estimation to continually refine a probabilistic estimate of the model count for a formula, so that each XOR-streamlined query yields as much information as possible. We implement this approach, with an approximate probability model, as a wrapper around an off-the-shelf SMT solver or SAT solver. Experimental results show that the implementation is faster than the most similar previous approaches which used simpler refinement strategies. The technique also lets us model count formulas over floating-point constraints, which we demonstrate with an application to a vulnerability in differential privacy mechanisms