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Conducting Polymers || Electrical Properties of Polymer Light-Emitting Devices
摘要： In this chapter, we present a brief introduction to semiconducting properties of conjugated polymers and the motivation to apply this class of materials in electronic/optoelectronic devices such as polymer light-emitting diodes (PLEDs). We describe, in detail, the operating mechanisms of PLEDs, with particular focus on the effects of charge injection and transport and their dependence on the external electric field and temperature. The mechanisms of current injection from the electrodes into the organic semiconductor are initially treated using traditional models for thermionic emission and tunnelling injection. More recent models considering the influence of metal/semiconductor interface recombination and of energetic and spatial disorder in the injection currents are also introduced and discussed. In addition, models considering space-charge-limited currents and trap-filling-limited currents are employed to describe the charge transport characteristics in the bulk. Furthermore, we present a brief discussion on ideas concerning the effects of the disorder on the charge-carrier transport behaviour.
关键词： space-charge-limited currents,conjugated polymers,polymer light-emitting diodes,organic semiconductors,electrical properties
更新于2025-09-19 17:15:36
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Space charge influence on particles channeling in optical lattice
摘要： In this paper the effect of a space charge on the dynamics of relativistic particles in a laser channel has been considered. We derived the expression for effective potential describing the dynamics of charged particles including into the study the interaction of particles with each other. Analysing general concepts on the distribution of a particle beam in a channel, we have formulated the condition, which determines the limits of applicability of the perturbation theory when space charge is taken into account.
关键词： Space charge,Lasers,Channeling,Ponderomotive potential,Quantum particle
更新于2025-09-19 17:15:36
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High charge carrier mobility in solution processed one-dimensional lead halide perovskite single crystals and their application as photodetectors
摘要： Organic inorganic hybrid metal halide perovskites have emerged as promising candidates for photovoltaics and light-emitting diodes. Recently, interest has been growing in the properties of low-dimensional metal halide perovskites, and one-dimensional versions with strong quantum confinement have demonstrated highly efficient broadband luminescence. Nevertheless, the charge transport mechanism in these low dimensional perovskites remains unclear. In this work, we characterised the charge mobility in one-dimensional perovskite single crystals using a space charge limited current method. Temperature dependent charge mobility measurements indicated that localized polarons at high temperature are replaced by delocalized polarons at low temperature with extended states in the polaronic band. A minimum mobility of 4.51 cm2/Vs was measured at room temperature. UV photodetectors based on these crystals show an ultrahigh photoresponsivity of 132.3 A W-1. These findings show the promise of high mobility low dimensional perovskite materials for optoelectronic applications.
关键词： space charge limited current,low-dimensional,charge transport,photodetectors,organic-inorganic hybrid metal halide perovskites
更新于2025-09-19 17:13:59
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A New Fabrication Method for Serpentine-Folded Waveguide Slow Wave Structure at W-Band
摘要： Thermionic energy converter (TEC) is a heat engine that generates electricity directly using heat as its source of energy and electron as its working fluid. Despite having a huge potential as an efficient direct energy conversion device, the progress in vacuum-based thermionic energy converter development has always been hindered by the space charge problem and the unavailability of materials with low work function. It is only recently that researchers have started to look back into this technology as recent advances in manufacturing technology techniques have made it possible to solve these problems, making TECs a viable option in replacing current energy production systems. The focus of this paper is to review the challenges of producing efficient and practical TECs, along with recent findings and developments in mitigating these challenges. Furthermore, this paper looked into potential applications of TECs, based on recent works and technologies, and found that, with certain improvements, it can be applied in many sectors.
关键词： nanowires,work function,thermionic energy conversion (TEC),space charge,Energy conversion efficiency
更新于2025-09-19 17:13:59
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Terahertz radiation from multi ion plasma irradiated by two cross focused Gaussian laser beams
摘要： Terahertz (THz) radiation generation by nonlinear coupling of two color Gaussian laser beams in a plasma with multi-ion species is numerically investigated by taking into account the nonlinearity due to ponderomotive force and space-charge field. By calculating the modification of electron density distribution of such plasma, coupled differential equations governing the evolution of two laser beams’ spot size and the outcome THz wave amplitude are established. The influence of the ionic species density and charge composition on the cross focusing of laser beams as well as generation of THz radiation is studied. The results mainly demonstrated that nonlinear effects in a multiply ionized plasma are excited stronger in comparison to the singly ionized one. It was found that the presence of ion species of higher charge enhances the cross focusing of beams and, consequently, THz field amplitude. The generated THz emission also strongly depends on the density of ionic species. The results showed that the minimum output of THz radiation is related to the higher density of singly charged ionic species. Moreover, it was found that the maximum value of THz amplitude takes place within a specific range of laser intensities.
关键词： multi-ion plasma,ponderomotive force,space-charge field,Terahertz radiation,Gaussian laser beams
更新于2025-09-19 17:13:59
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Manipulation of Laser Distribution to Mitigate the Space-Charge Effect for Improving the Performance of a THz Coherent Undulator Radiation Source
摘要： A THz coherent undulator radiation (THz-CUR) source has been developed at the Institute of Advanced Energy, Kyoto University. A photocathode Radio-Frequency (RF) gun and a bunch compressor chicane are used for generating short-bunch electron beams. When the electron beam energy is low, the space-charge effect strongly degrades the beam quality, such as the bunch length and the energy spread at the high bunch charge condition at around 160 pC, and results in the reduction of the highest frequency and the maximum radiated power of the THz-CUR. To mitigate the space charge effect, we have investigated the dependence of the electron beam quality on the laser distribution in transverse and longitudinal directions by using a numerical simulation code, General Particle Tracer GPT. The manipulation of the laser distribution has potential for improving the performance of the THz-CUR source. The electron bunch was effectively compressed with the chicane magnet when the laser transverse distribution was the truncated Gaussian pro?le, illuminating a cathode. Moreover, the compressed electron bunch was shortened by enlarging the laser pulse width. Consequently, an enhancement of the radiated power of the THz-CUR has been indicated.
关键词： manipulation of laser distribution,performance,coherent undulator radiation (CUR),space charge effect
更新于2025-09-16 10:30:52
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The role of moisture in the preparation for efficient planar perovskite solar cells
摘要： Perovskite solar cells (PSC) have achieved a certificated efficiency of 25.2% within the past few years. Among effective methods, one of the most effective approaches obtaining highly-efficient PSCs is the moisture-assisted annealing process. However, the role of moisture in the preparation of high-performance PSCs is under intense debate. Herein the critical effect of moisture in the preparation of efficient Formamidinium (FA) based PSCs with improved-quality perovskite films is systematically investigated based on diverse characterizations. Consequently, the optimal amount of moisture is determined at 50% relative humidity (RH) which produces perovskite films of higher quality with larger and uniform grains size in comparison to the control films prepared in the glovebox. Specifically, prolonged lifetime, reduced defects densities and higher light harvesting capability of perovskite films annealed in 50RH% are confirmed by the photoluminescence (PL), the time-resolved PL (TRPL), the space charge limited current (SCLC) and the confocal laser scanning microscopy (CLSM), respectively. These results indicate the environments with a controlled level of moisture is preferable for achieving high-quality perovskite films and the compatibility of fabricating highly-efficient PSCs under ambient conditions with controlled moisture for future industrial mass production.
关键词： defects density,two-step deposition,Planar perovskite solar cells,moisture,space-charge-limited current
更新于2025-09-16 10:30:52
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Two-frequency laser with distributed feedback formed by a space charge wave
摘要： The regimes of amplification and generation of optical TE waves arising on a grating formed by a space charge wave (SCW) in a plane optical waveguide based on an n-GaAs semiconductor are considered. For the perturbed n-GaAs waveguide, the reflectance and transmittance of TE modes with the same indices (m = n = 0) are calculated depending on the pump level and length of interaction between the optical and SCWs. It is shown that even with a relatively small depth of modulation of the dielectric constant (Δ?? ≈ 10?5) under conditions of high optical pumping (with an amplification factor ?? ≈ 150 cm?1) and corresponding SCW-optical interaction length, there is a possibility of not only amplification, but also generation of forward and backward optical modes at a wavelength of 10.6?μm. The results can be used to create tunable semiconductor laser generators based on the SCW-optical interaction and operating in the near and mid-IR range.
关键词： Semiconductor waveguide,GaAs,Space charge wave,Laser generation
更新于2025-09-12 10:27:22
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Through-space charge transfer in luminophore based on phenyl-linked carbazole- and phthalimide moieties utilized in cyan-emitting OLEDs
摘要： Two new carbazole-containing aromatic imides were synthesized by three-step synthetic pathway with the moderate yields up to 76%. The compounds were investigated theoretically. TD-DFT computational studies revealed low singlet-triplet energy di?erences. The compounds were found to have relatively high thermal stability with 5% mass loss temperatures in the range of 280–310 °C. Phthalimide-based compound exhibited aggregation-induced emission enhancement and thermally activated delayed ?uorescence with photo-luminescence quantum e?ciency of 20% in the solid state. Structure-properties relationship of this compound was investigated and it was found that charge-transfer through space mechanism is responsible for the emission. Series of green-emitting doped and non-doped electroluminescent devices were fabricated based on the carbazole-phthalimide derivative were fabricated to reveal best-performing mCP-doped device demonstrating maximum external quantum e?ciency of 2.4% with current e?ciency of 6.6 cd/A and power e?ciency of 4.0 lm/W with maximum brightness of 8300 cd/m2.
关键词： Cyan-emitting OLED,Aromatic imide,Through-space charge transfer,Aggregation-induced emission enhancement,Thermally activated delayed ?uorescence
更新于2025-09-12 10:27:22
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AIP Conference Proceedings [AIP Publishing PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019 - Kerala, India (12–14 June 2019)] PROCEEDINGS OF THE INTERNATIONAL CONFERENCE ON ADVANCED MATERIALS: ICAM 2019 - Measurement of hole mobility in P3HT based photovoltaic cell using space charge limited current method
摘要： Mobility of carriers is one of the pivotal parameters characterizing any semiconducting material and it is important for organic semiconductors too. The mobility of organic semiconductors remains far less when compared to inorganic counterparts and hence attempts in the direction improvise it carries tremendous significance. This paper investigates the positive charge carriers transport properties in a bulk heterojunction organic photovoltaic cell using two different Anode Buffer Layers (PEDOT:PSS and MoO3). The method of Space Charge Limited Current (SCLC) is used to compute the hole mobilities and also the values are compared. The values obtained with PEDOT:PSS and MoO3 as HTLs are 1.043x10-4 cm2 V-1S-1 and 1.357x10-4 cm2V-1S-1 respectively. It is seen that the device with higher carrier mobility exhibits better performance.
关键词： PEDOT:PSS,hole mobility,space charge limited current,MoO3,photovoltaic cell,P3HT
更新于2025-09-12 10:27:22