Electrical and environmental parameters of the performance of polymer solar cells based on P3HT:PCBM

The electrical and environmental parameters of polymer solar cells (PSC) provide important information on their performance. In the present article we study the influence of temperature on the voltage-current (I-V) characteristic at different temperatures from 10 °C to 90 °C, and important parameters like bandgap energy Eg, and the energy conversion efficiency η. The one-diode electrical model, normally used for semiconductor cells, has been tested and validated for the polemeral junction. The PSC used in our study are formed by the poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61-butyric acid methyl ester (PCBM). Our technique is based on the combination of two steps; the first use the Least Mean Squares (LMS) method while the second use the Newton-Raphson algorithm. The found results are compared to other recently published works, they show that the developed approach is very accurate. This precision is proved by the minimal values of statistical errors (RMSE) and the good agreement between both the experimental data and the I-V simulated curves. The obtained results show a clear and a monotonic dependence of the cell efficiency on the studied parameters

Viscosity and Rheological Properties of Graphene Nanopowders Nanofluids

The dynamic viscosity and rheological properties of two different non-aqueous graphene nano-plates-based nanofluids are experimentally investigated in this paper, focusing on the effects of solid volume fraction and shear rate. For each nanofluid, four solid volume fractions have been considered ranging from 0.1% to 1%. The rheological characterization of the suspensions was performed at 20°C, with shear rates ranging from 10⁻¹ s⁻¹ to 10³s⁻¹, using a cone-plate rheometer. The Carreau–Yasuda model has been successfully applied to fit most of the rheological measurements. Although it is very common to observe an increase of the viscosity with the solid volume fraction, we still found here that the addition of nanoparticles produces lubrication effects in some cases. Such a result could be very helpful in the domain of heat extraction applications. The dependence of dynamic viscosity with graphene volume fraction was analyzed using the model of Vallejo et al

Viscosity of graphene in lubricating oil, ethylene glycol and glycerol

This paper reports the results of an experimental investigation of graphene particle suspensions in lubricating oil, ethylene glycol and glycerol-based fluids. Graphene particles of different specific surface area show variation in the viscosity depending on the shear rate and the temperature. The lubricating effect, e.g., reduction in the viscosity compared to the base fluid, is observed for the concentration (below 0.4 mass%) in lubricating oil and glycerol. In the range of parameters studied (e.g., concentration below 1 mass% and temperature up to 80 °C), the activation energy slightly decreases. The enhancement of viscosity with graphene volume fraction is larger for ethylene glycol. Graphical abstract: [Figure not available: see fulltext.] © 2023, Akadémiai Kiadó, Budapest, Hungary

Ab Initio Study of the Electronic and Energy Properties of Diamond Carbon

In this chapter, we present a study on the electronic properties of diamond carbon, using band structure and density of states calculations. The calculations are based on the use of the grid-based projector-augmented wave (GPAW) and atomic simulation environment (ASE) methods. The main results of our work are the optimization of diamond energy (to −17.57 eV) and the calculation of the gap with the PBE (Perdew, Burke, and Ernzerhof) and the functional hybrid PBE0 hybrid functional, which is about 5.368 eV (the closest value to the value found in the literature). We were also able to reproduce the experimental value of the lattice constant of diamond to within 0.2% for PBE0 and 0.4% for PBE. Our results contribute to the study of the electronic properties of diamond using GPAW and ASE simulation, which is a set of Python modules, designed to facilitate the setup, execution, and analysis of atomic/electronic calculations. This tight integration of ASE and GPAW should be exploited in future research of the electronic properties of diamond, which is one of the most promising materials for the integrated electronic and photonic, radio, optoelectronic, and quantum devices industry. This chapter provides interesting information for the theoretical and experimental communities working in this field

Drying colloidal systems: laboratory models for a wide range of applications

The drying of complex fluids provides a powerful insight into phenomena that take place on time and length scales not normally accessible. An important feature of complex fluids, colloidal dispersions and polymer solutions is their high sensitivity to weak external actions. Thus, the drying of complex fluids involves a large number of physical and chemical processes. The scope of this review is the capacity to tune such systems to reproduce and explore specific properties in a physics laboratory. A wide variety of systems are presented, ranging from functional coatings, food science, cosmetology, medical diagnostics and forensics to geophysics and art

Propriétés électroniques de tubules et d'échantillons contenant des nanotubules carbonés

This work presents theoretical studies about elastic stress affects on electronic properties of carbon nanotubes. A model taking into account the curvature induced by conformal mapping has been estblished in the framework of a tight-binding scheme. This model has been used with usual boundary conditions to compute an analytic expression of the electronic density of states (DOS) by the Green's function method. Our results show that curvature is responsible for a gap opening in the DOS. This modification of the electronic properties of tubules is a kind of Peierls instability. Influence of uniaxial stress on armchair and zigzag nanotubes has been investigated. Our results show new electronic properties and semiconductor to metal transitions with pressure or tractionNous présentons dans ce mémoire une étude théorique concernant l'influence de certaines déformations élastiques sur les propriétés électroniques de nanotubules carbones. Nous avons tout d'abord cherche a modéliser le rôle de la courbure induite par la déformation d'un plan de graphène pour former un tubule. Pour cela, nous avons étudié la modification des paramètres de transfert qu'entraine une déformation cylindrique dans l'approximation des liaisons fortes. Nous proposons un potentiel de perturbation qui intègre le couplage entre le défaut d'alignement des orbitales qui composent les liaisons et les intégrales de transfert entre les orbitales de deux atomes de carbone plus proches voisins dans le plan de graphène. En utilisant le modèle précédent et les conditions de périodicité a la circonférence du cylindre nous avons étudié, par la méthode des fonctions de green, la densité des états électroniques des nanotubules zigzag et armchair. Nous avons en particulier montre que la courbure était responsable, pour une catégorie de nanotubules, d'une forme d'instabilité de Peierls ouvrant un gap non négligeable dans le spectre énergétique des électrons. Nous avons applique le formalisme précédent a l'étude de l'influence d'une déformation élastique axiale sur les propriétés électroniques des tubules. Nous avons calculé des pressions de transition semiconducteur métal expérimentalement réalisables. Nos calculs montrent surtout des résultats nouveaux surprenants, puisque la sensibilité du gap des tubules zigzag (n,0) a la contrainte uniaxiale change de signe selon que n=3q-1 ou n=3q+1. Nous proposons une explication physique simple de cette nouvelle propriét

Numerical Solution of Linear Second-Kind Convolution Volterra Integral Equations Using the First-Order Recursive Filters Method

A new numerical method for solving Volterra linear convolution integral equations (CVIEs) of the second kind is presented in this work. This new approach uses first-order infinite impulse response digital filters method (IIRFM). Three convolutive kernels were analyzed, the unit kernel and two singular kernels: the logarithmic and generalized Abel kernels. The IIRFM is based on the combined use of the Laplace transformation, a first-order decomposition, and a bilinear transformation. This approach often leads to simple analytical expressions of the approximate solutions, enabling efficient numerical calculation, even using single-precision floating-point numbers. When compared with the method of homotopic perturbations with Laplace transformation (HPM-L), the IIRFM approach does not present, in linear cases, the convergence difficulties inherent to iterative approaches. Unlike most solution methods based on the Laplace transform, the IIRFM has the dual advantage of not requiring the calculation of the Laplace transform of the source function, and of not requiring the systematic calculation of inverse Laplace transforms

One-Dimensional Systemic Modeling of Thermal Sensors Based on Miniature Bead-Type Thermistors

Accurate measurements of thermal properties is a major concern, for both scientists and the industry. The complexity and diversity of current and future demands (biomedical applications, HVAC, smart buildings, climate change adapted cities, etc.) require making the thermal characterization methods used in laboratory more accessible and portable, by miniaturizing, automating, and connecting them. Designing new materials with innovative thermal properties or studying the thermal properties of biological tissues often require the use of miniaturized and non-invasive sensors, capable of accurately measuring the thermal properties of small quantities of materials. In this context, miniature electro-thermal resistive sensors are particularly well suited, in both material science and biomedical instrumentation, both in vitro and in vivo. This paper presents a one-dimensional (1D) electro-thermal systemic modeling of miniature thermistor bead-type sensors. A Godunov-SPICE discretization scheme is introduced, which allows for very efficient modeling of the entire system (control and signal processing circuits, sensors, and materials to be characterized) in a single workspace. The present modeling is applied to the thermal characterization of different biocompatible liquids (glycerol, water, and glycerol–water mixtures) using a miniature bead-type thermistor. The numerical results are in very good agreement with the experimental ones, demonstrating the relevance of the present modeling. A new quasi-absolute thermal characterization method is then reported and discussed. The multi-physics modeling described in this paper could in the future greatly contribute to the development of new portable instrumental approaches