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- 2018
- electron-transparent membranes
- micropump
- field emission electron source
- ion source
- ion mobility spectrometry
- Optoelectronic Information Science and Engineering
- Wroclaw University of Science and Technology
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38.1: Quantitative Analysis of Charge Transport in Single‐Carrier Devices and OLEDs Combining DC and AC Data
摘要： Single-carrier devices are perfect model systems to extract material parameters for more complex multilayer organic light-emitting diodes (OLEDs) and to learn about charge transport and injection properties of the device. By combining simulation and measurements in steady-state and frequency domain, we obtain a set of reliable material parameters which can be used to model the multilayer OLED structure. Moreover, we can also evaluate the contact behavior and conclude that the OLED operation is limited by electron transport.
关键词： characterization,organic light-emitting diode,mobility,material parameter,doping
更新于2025-09-12 10:27:22
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Modulated Photocurrent Spectroscopy for Determination of Electron and Hole Mobilities in Working Organic Solar Cells
摘要： carrier drift mobility is an important physical constant in the charge transport process of organic solar cells (OSCs). Although time-of-flight and space-charge-limited current techniques have been frequently utilized for mobility measurements, the validity of a new method using modulation photocurrent spectroscopy is discussed in this contribution. The advantages of this method are its applicability to working OSCs with optimized device structures and the simultaneous determination of the electron and hole mobilities. These features make it possible to study the relation between the mobility balance and the solar cell characteristics, such as the power conversion efficiency, using only a single working OSC; hence, it is not necessary to fabricate electron-only and hole-only devices for mobility measurements. After carrying out numerical simulations to examine the validity of this method for mobility determination, the dependence of the mobility balance on the mixing ratio of the electron-donor and –acceptor materials is presented.
关键词： organic solar cells,carrier drift mobility,modulation photocurrent spectroscopy,power conversion efficiency,electron and hole mobilities
更新于2025-09-12 10:27:22
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Analytical modelling and parameters extraction of multilayered OLED
摘要： This research study investigates electrical performance of the multilayered organic light-emitting diode (OLED) with a focus on the role of charge injection, transport and emission layers. Device parameters; luminescence and current density are extracted using Silvaco ATLAS numerical device simulator and validated through the fabricated experimental results with a minor deviation of 3%. Furthermore, a mathematical model is applied to extract other device parameters such as electric field, charge carrier mobility, concentration and current density. Additionally, the multilayered device architecture is critically analysed through cut line methodology to better comprehend the internal device physics in terms of hole-electron mobility, concentration and their recombination. Subsequently, the performance parameters extracted using analytical model are compared with the results of internal analysis and a close match is observed. These results prove the Poole-Frenkel mobility-dependent behaviour in the OLEDs that varies following electric field. Analyses also highlight high electron and hole concentrations in the vicinity of the emission layer as a reason of high luminescence in the multilayered OLED, directly following the Langevin's theory of recombination in organic semiconductors. These analyses highlight the impact of different layers in the OLEDs and thus open up new horizons to further performance improvement in these devices.
关键词： Silvaco ATLAS,multilayered OLED,Poole-Frenkel mobility model,charge injection,Langevin's recombination model,transport and emission layers
更新于2025-09-12 10:27:22
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A Noble Metal Dichalcogenide for High‐Performance Field‐Effect Transistors and Broadband Photodetectors
摘要： 2D layered materials are an emerging class of low-dimensional materials with unique physical and structural properties and extensive applications from novel nanoelectronics to multifunctional optoelectronics. However, the widely investigated 2D materials are strongly limited in high-performance electronics and ultrabroadband photodetectors by their intrinsic weaknesses. Exploring the new and narrow bandgap 2D materials is very imminent and fundamental. A narrow-bandgap noble metal dichalcogenide (PtS2) is demonstrated in this study. The few-layer PtS2 field-effect transistor exhibits excellent electronic mobility exceeding 62.5 cm2 V?1 s?1 and ultrahigh on/off ratio over 106 at room temperature. The temperature-dependent conductance and mobility of few-layer PtS2 transistors show a direct metal-to-insulator transition and carrier scattering mechanisms, respectively. Remarkably, 2D PtS2 photo detectors with broadband photodetection from visible to mid-infrared and a fast photoresponse time of 175 μs at 830 nm illumination for the first time are obtained at room temperature. Our work opens an avenue for 2D noble-metal dichalcogenides to be applied in high-performance electronic and mid-infrared optoelectronic devices.
关键词： broadband photodetection,PtS2,on-off ratio,field-effect transistors,mobility
更新于2025-09-12 10:27:22
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Band-like electron transport in 2D quantum dot periodic lattices: the effect of realistic size distributions
摘要： Electron mobility in nanocrystal films has been a controversial topic in the last few years. Theoretical and experimental studies evidencing carrier transport by hopping or showing band-like features have been reported in the past. A relevant factor to analyze transport results is the progressive improvement leading to better regimented structures for which band-like transport would be more relevant. This work presents an efficient model to compute temperature-dependent band-like electronic mobilities in 2D quantum dot arrays when a realistic quantum dot size distribution is considered. Comparisons with experimental results are used to estimate these size distributions, in good agreement with data of the samples.
关键词： quantum dot arrays,size distribution,band-like transport,electron mobility,nanocrystal films
更新于2025-09-12 10:27:22
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Simulating nanocrystal-based solar cells: A lead sulfide case study
摘要： Nanocrystal-based solar cells are promising candidates for next generation photovoltaic applications; however, the most recent improvements to the device chemistry and architecture have been mostly trial-and-error based advancements. Due to complex interdependencies among parameters, determining factors that limit overall solar cell efficiency are not trivial. Furthermore, many of the underlying chemical and physical parameters of nanocrystal-based solar cells have only recently been understood and quantified. Here, we show that this new understanding of interfaces, transport, and origin of trap states in nanocrystal-based semiconductors can be integrated into simulation tools, based on 1D drift-diffusion models. Using input parameters measured in independent experiments, we find excellent agreement between experimentally measured and simulated PbS nanocrystal solar cell behavior without having to fit any parameters. We then use this simulation to understand the impact of interfaces, charge carrier mobility, and trap-assisted recombination on nanocrystal performance. We find that careful engineering of the interface between the nanocrystals and the current collector is crucial for an optimal open-circuit voltage. We also show that in the regime of trap-state densities found in PbS nanocrystal solar cells (～1017 cm?3), device performance exhibits strong dependence on the trap state density, explaining the sensitivity of power conversion efficiency to small changes in nanocrystal synthesis and nanocrystal thin-film deposition that has been reported in the literature. Based on these findings, we propose a systematic approach to nanocrystal solar cell optimization. Our method for incorporating parameters into simulations presented and validated here can be adopted to speed up the understanding and development of all types of nanocrystal-based solar cells.
关键词： nanocrystal-based solar cells,simulation,charge carrier mobility,lead sulfide,drift-diffusion models,trap states
更新于2025-09-12 10:27:22
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The effects of layer thickness and charge mobility on performance of FAI:MABr:PbI <sub/>2</sub> :PbBr <sub/>2</sub> perovskite solar cells: GPVDM simulation approach
摘要： The perovskite solar cells (PSCs) have been extensively interested and its performance has rapidly increased up to 24.2 %. Layer thickness and charge mobility are crucial for high-performance perovskite solar cells. In this paper, we study the effect of layer thickness and charge mobilities on some parameters in perovskite solar cell based on structure of FTO/TiOx/SnO2/FAIMABrPbI2PbBr2/Spiro-OMeTAD/Ag by using the GPVDM (General- purpose Photovoltaic Device Model) software. The simulation results show that the best optimized power conversion efficiency of 23.88 % can be obtained. The optimal layer thickness in the simulation of TiOx, SnO2, FAIMABrPbI2PbBr2, Spiro-OMeTAD are 50 nm, 30 nm, 400 nm, 30 nm, respectively. The optimal electron and hole mobilities of photoactive layer are 2?10-5 m2V-1s-1and 2?10-6 m2V-1s-1, respectively. Comparative study of simulation and experiment are observed, that performance of 15.93 % of efficiency can be experimentally achieved, however the model of this solar cell is observed 18.43 % of efficiency by simulation.
关键词： layer thickness,GPVDM simulation,perovskite solar cells,power conversion efficiency,charge mobility
更新于2025-09-12 10:27:22
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A Machine‐Learning Based Design Rule for Improved Open‐Circuit Voltage in Ternary Organic Solar Cells
摘要： Organic solar cells (OSCs) based on ternary blend active layers are among the most promising photovoltaic technologies. To further improve the power conversion efficiency (PCE), the materials selection criteria must be focused on achieving high open-circuit voltage (Voc) through the alignment of the energy levels of the ternary blend active layers. Hence, machine-learning approaches are in high demand for extracting the complex correlation between Voc and the energy levels of the ternary blend active layers, which are crucial to facilitate device design. In the present work, the data-driven strategies are used to generate a model based on the available experimental data and the Voc are then predicted using available machine-learning methods (Random Forest regression and Support Vector regression). In addition, the Random Forest regression is compared with Support Vector regression to demonstrate the superiority of Random Forest regression for Voc prediction. The Random Forest regression is then developed to find the appropriate energy level alignment of ternary OSCs and to reveal the relationship between Voc and electronic features. Finally, an analysis based on the ranking of variables in terms of importance by the Random Forest model is performed to identify the key feature governing the Voc and the performance of ternary OSCs. From the perspective of device design, the machine-learning approach provides sufficient insights to improve the VOC and advances the comprehensive understanding of ternary OSCs.
关键词： organic field-effect transistors,Machine-learning,charge transport mobility.
更新于2025-09-12 10:27:22
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High-performance p-channel thin-film transistors with lightly doped n-type excimer-laser-crystallized germanium films
摘要： High-performance polycrystalline-germanium (poly-Ge) thin-film transistors (TFTs) fabricated with lightly doped Ge thin films by excimer laser crystallization (ELC) and counter doping (CD) have been demonstrated. High-quality n-type Ge thin films with a grain size as large as 1 μm were fabricated by ELC in the super lateral-growth regime and CD at a dose of 1 × 1013 cm?2 or higher. Consequently, a superior field-effect mobility of 271 cm2 V?1 s?1 and a high on/off current ratio of 2.7 × 103 have been obtained for p-channel Ge TFTs with the channel width and length of both 0.5 μm fabricated by ELC at 300 mJ/cm2 and CD at a dose of 1 × 1013 cm?2. The effects of ELC conditions and CD dose on the electrical characteristics of p-channel Ge TFTs were also investigated.
关键词： field-effect mobility,excimer laser crystallization,thin-film transistors,polycrystalline-germanium,counter doping
更新于2025-09-11 14:15:04
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Two-terminal terahertz detectors based on AlGaN/GaN high-electron-mobility transistors
摘要： We report an approach to make two-terminal antenna-coupled AlGaN/GaN high-electron-mobility-transistor self-mixing terahertz detectors. Fluorine ion implantation is used to increase the threshold voltage of the AlGaN/GaN two-dimensional electron gas. An optimal implantation dose can be reached so that the detector responsivity is maximized at zero gate voltage or with the gate ?oating. The relationship between the ion dosage and the threshold voltage, electron mobility, electron density, responsivity, and noise-equivalent power (NEP) is obtained. A minimum optical NEP of 47 W= ??????Hz is achieved from a two-terminal detector at 0.65 THz. The capability of two-terminal operation allows for the design of a large array of antenna-coupled high-electron-mobility transistor detectors without the demanding needs of routing negative gate voltage lines around the antenna array and minimizing the gate leakage current.
关键词： two-terminal operation,terahertz detectors,AlGaN/GaN,fluorine ion implantation,high-electron-mobility transistors
更新于2025-09-11 14:15:04