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Designing composition tuned glasses with enhanced properties for use as substrate in Cu2ZnSnS4 based thin film solar cells
摘要： Glass substrate constituents play a very important role in CuInGaSe2/Cu2ZnSnS4 thin film solar cell. The diffusion of Na from soda lime glass substrate (SLG) reportedly passivates the grain boundaries of the absorber layers that prevent recombinations of electrons & holes at the grain boundaries. Thus, glasses with various alkali metal oxides (Na/Li/K) have been synthesized and characterized using various experimental techniques to understand the structure-property correlation and its effect on the diffusion phenomenon. The as-prepared glasses for substrate are thermally and mechanically more stable, with better conductivity and higher diffusivity than commercially available soda lime glass (SLG). The present glasses exhibit suitable properties for use as substrate for thin film solar cell.
关键词： Conductivity,Substrate,Solar cell,SLG,Glass
更新于2025-09-16 10:30:52
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Passivation, conductivity, and selectivity in solar cell contacts: Concepts and simulations based on a unified partial-resistances framework
摘要： Passivation, conductivity, and selectivity are often acknowledged as the three requirements for optimal contacts to photovoltaic solar cells. Although there are generally accepted definitions and metrics for passivation and conductivity, a common understanding of the concept of selectivity is emerging only now. In this contribution, we present a generalized model of solar cell contacts based on the distinct lumped resistances encountered by electrons and holes traversing a contact, which we refer to as partial specific contact resistances. The relations between electron and hole partial current densities, quasi-Fermi level separation, and external voltage are derived from these partial specific contact resistances, leading to simple metrics for the aforementioned contact properties: the sum of the electron and hole resistances is a metric for passivation, their ratio is a metric for selectivity, and the majority-carrier resistance is a metric for conductivity. Using PC1D, we validate our model by simulating 10 500 cases of homojunction contacts to crystalline silicon solar cells, although our framework is material agnostic and can be equally applied to any other type of absorber. In these simulations, the hole contact and absorber are assumed to be ideal, whereas we vary the partial specific contact resistances in the electron contact by orders of magnitude by adjusting the electron and hole mobilities, their densities (through variations of the donor doping density), and the contact thickness. The simulations confirm the finding of the model that, when the contact fraction cannot be adjusted—as is the case with full-area contacts—combined passivation and conductivity are necessary and sufficient for optimal solar cell performance, and they imply selectivity. However, the reciprocal is not true: contacts can be selective but lack conductivity—causing a deleterious drop in fill factor—or can be selective but provide poor passivation—leading to a reduction in implied open-circuit voltage and, hence, actual open-circuit voltage. Thus, selectivity is a meaningful metric in the sole case of partial-area contacts, where the contact fraction can be adjusted arbitrarily.
关键词： solar cell contacts,crystalline silicon,partial specific contact resistances,conductivity,selectivity,PC1D simulations,passivation
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Including the Effects of Covering Layers in the Determination of Graphene Conductivity from THz-TDS Measurements
摘要： We investigate the effects of covering layers on the determination of graphene conductivity from THz-TDS measurements. Especially the errors arising from the common approach to neglect those layers in the determination process are addressed. To counteract those errors an expanded determination method, based on the classical thin-film approach is introduced.
关键词： thin-film approximation,graphene conductivity,THz-TDS measurements,covering layers
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Modulation Behaviors, Conductivities, and Carrier Dynamics of Single and Multilayer Graphenes
摘要： Time domain and time resolved terahertz studies of single- and multi-layer graphene (SLG and MLG) samples and modulator devices will be presented. A high performance up to 100% of modulators were observed with the devices even at very low voltages. High modulation depth over such a broad spectrum and simple device structure brings significant importance toward application of this type of device in THz and related technologies. In addition, conductivities of SLG and MLG devices were also investigated and a change in behavior was observed as the layer thickness increased. The charge carriers dynamics of the samples with pulp fluence and color was also highly interesting.
关键词： modulator,carrier dynamics,conductivity,terahertz,graphene
更新于2025-09-16 10:30:52
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[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Intraband Ultrafast Terahertz Conductivity Dynamics in Graphene
摘要： The cooling mechanism is crucial for nanoelectronics, which determines the response time limited for the devices. The cooling process after optical pump in graphene, which is a well-known material with ultrahigh carrier mobility, is therefore an urgent research topic. Ultrafast thermalization and relaxation process in a monolayer graphene film grown on a quartz substrate is investigated by femtosecond laser pump, terahertz probe induced negative technique. A typical photo found, and the electron-phonon-impurity supercollision process is determined to about 2.8 picosecond at different pump photon energy and pump fluence. The competition between the impurity supercollision and the interband-intraband scattering in graphene could give new insight into the design of the application of graphene photonic devices.
关键词： ultrafast dynamics,cooling mechanism,electron-phonon-impurity supercollision,terahertz conductivity,graphene
更新于2025-09-16 10:30:52
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Decay Kinetics of Thermal Radiation Emitted by Surface Layers of Carbon Materials under Pulsed Laser Excitation
摘要： The decay of thermal radiation emitted by surface layers of carbon materials excited by pulses of a Q-switched neodymium laser is investigated experimentally and theoretically. It is discovered that the decay curves can be approximated with satisfactory accuracy by a sum of two exponential components with decay times of about 10 and 100 ns. Changes in the decay curves under sample irradiation by a sequence of laser pulses can be interpreted as being the result of redistribution of intensities of these two components. Based on the results of computer simulation, the conclusion is drawn that the glow-decay time is determined by the ratio of the penetration depth of the laser radiation and the thermal-diffusion length, which creates an opportunity to determine the coefficient of temperature conductivity in a thin surface layer of the studied material at high temperatures (thousands of Kelvins).
关键词： decay kinetics,temperature conductivity,pulsed laser excitation,carbon materials,thermal radiation
更新于2025-09-16 10:30:52
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Thermal and Physical Performance of Heat Sink for Light-Emitting Diode Improved with Expanded Graphite
摘要： In this study, the fabrication of working expanded graphite based heat sink was carried out as follows. Briefly, the round heat sink were composed of graphite as an active material, Cu and Al as heat transfer enhancement material and resin as a binder. The prepared round heat sinks were characterized by X-ray diffraction and scanning electron microscopy. After chemical intercalation treatment and heat treatment at 673-1073 K, it was clearly seen that the spacing of the interlayers of graphite flakes increased. The metal modified graphite heat sinks in our experiment exhibited a good rate of capability in physical performances. Sample GA10-400 showed a best and most high density, highest thermal diffusivity and thermal conductivity
关键词： Physical performance,Density,Thermal diffusivity and conductivity,Graphite,Heat transfer
更新于2025-09-16 10:30:52
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Influence of 2-Amino-4-methylpyridine and 2-Aminopyrimidine Ligands on the Malonic Acid-Cu(II) System: Insights through Supramolecular Interactions and Photoresponse Properties
摘要： Two Cu(II)-malonate complexes with 2-amino-4-methylpyridine (complex 1) and 2-aminopyrimidine (complex 2) auxiliary ligands were synthesized, and their single-crystal X-ray diffraction structures were established. Change in the auxiliary ligand exhibits substantial structural variation in the present complexes. Complex 1 shows a one-dimensional anionic copper-malonate moiety connected by the malonate bridge, whereas complex 2 is a mononuclear one. For both the complexes, auxiliary ligands are attached with the Cu-malonate moiety through various noncovalent interactions. Optical band gap, electrical conductivity, and photosensitivity of complexes 1 and 2 were measured, but the values of electrical parameters of the complexes significantly differ from each other. However, the magnitudes of electrical parameters increase several times for both the complexes when they are exposed under visible light, though the values of light sensing parameters of complex 1 were found to be higher than those of complex 2. Density functional theory calculations for complex 1 were carried out to support the experimental result.
关键词： 2-aminopyrimidine,electrical conductivity,Cu(II)-malonate complexes,density functional theory,2-amino-4-methylpyridine,optical band gap,noncovalent interactions,photosensitivity
更新于2025-09-16 10:30:52
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Self-assembled monolayers of polyoxovanadates with phthalocyaninato lanthanide moieties on gold surfaces
摘要： The two first representatives of phthalocyaninato (Pc) lanthanide-ligated polyoxovanadate cages {[V12O32(Cl)](LnPc)n}n(cid:2)5 (n = 1 or 2, Ln = Yb3+) were synthesised and fully characterised. These magnetic complexes form two-dimensional self-assembled monolayers exhibiting electrical conductivity on gold substrate surfaces, as assessed by using an EGaIn tip.
关键词： gold surfaces,electrical conductivity,phthalocyaninato lanthanide,polyoxovanadates,self-assembled monolayers
更新于2025-09-16 10:30:52
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Graphene Photonics || Electronic Properties
摘要： The ?ow of free charge carriers, i.e., electrons in the conduction band or holes in the valence band, in a semiconductor that is subject to an electric ?eld is accelerated by the electric field but is hindered by scattering events. In a semiconductor, free carriers accelerate in the presence of an electric field. The randomly distributed scattering centers, such as impurities and defects, act as a counter force that decelerates and de?ects the carriers. When the steady state is eventually reached under a constant electric field, a constant ?ow of carriers is achieved. In graphene, by contrast, charge carriers on the Dirac cone have a constant speed and do not accelerate or decelerate in response to the electric field or the scattering centers; instead, the effect of the electric field is rather to align the motion of carriers to the direction of the electric field, and the scattering centers act as a source to disturb this alignment process. This process is well captured by the Boltzmann transport equation, which has successfully described many statistical behaviors of carriers in metals and semiconductors. The purpose of this chapter is to describe the electronic properties of graphene, starting from the Boltzmann transport equation.
关键词： Boltzmann transport equation,charge carriers,electric field,electronic properties,conductivity,scattering events,graphene,two-dimensional material
更新于2025-09-16 10:30:52