Highly efficient ultrathin plasmonic insulator-metal-insulator-metal solar cell

Nano-porous ultrathin plasmonic insulator-metal-insulator-metal (IMIM) solar cell with high power conversion efficiency up to 7% in broad wavelength range from 300 to 750 nm was theoretically studied. The proposed IMIM design allows to choose various bottom insulators with desired barrier height of metal-insulator interface due to independence of the total absorbance on the bottom insulator. IMIM structure shows 73.8% difference in the average absorbance between the top and bottom metal layers with 1-nm bottom insulator. Moreover, the incident light decreases the absorbance negligibly up to 35 degrees for both TE and TM modes and by 17.5% at 70 degrees. Furthermore, the absorption between TE and TM modes differs by less than 5%, which indicates the structure as polarization independent. Our results indicate IMIM design benefit in plasmonic solar cells demanding low thickness, flexibility, low-cost, and polarization independence. Moreover, this structure can be implemented for integrated optical circuits as well as for solar thermoelectric generator

Optoelectronic performance of AgNW transparent conductive films with different width-to-height ratios and a figure of merit embodying an optical haze

Transparent conductive films (TCFs) based on rectangularly shaped silver nanowires (AgNWs) with different width-to-height ratios were theoretically studied. We show that tall AgNWs (height > width) possess higher transmittance and lower sheet resistance compared to other configurations of AgNWs. Moreover, tall AgNWs possesses significantly higher optical haze, which makes them a transparent conductor of choice for thin solar cell applications. For applications requiring low haze such as displays and touch screens, we propose an updated figure of merit embodying transmittance, sheet resistance and haze, allowing tuning width-to-height ratio to achieve a reasonable AgNW TCF performance trade-off. Obtained results offer a means for deeper analysis of AgNW properties for many optoelectronic applications

Effect of silver nanowire length in a broad range on optical and electrical properties as a transparent conductive film

Optical and electrical properties of silver nanowire transparent conductive films with a broad range of nanowire lengths were studied. A proposed simulation model demonstrated similar behavior with experimental results for 30 and 90 μm nanowires, and thus it was used to expand the range of nanowire lengths from 10 to 200 μm. Theoretical results show that a lengthening of silver nanowires results in an increase of their optoelectronic performance; 200 μm long nanowire possess 13.5 times lower sheet resistance compared to 10 μm ones, while the transmittance remains similar for coverage densities of nanowires up to 25%. Moreover, the dependence of the sheet resistance on the length of nanowires changes non-linearly; from 10 to 20 µm, 20 to 80 µm and 80 to 200 µm the sheet resistance drops by a factor of 5, 2.25 and 1.2 respectively. Furthermore, a thickening of nanowire diameters from 30 to 90 nm decreases the sheet resistance to 5.8 times. Obtained results allow a deeper analysis of the silver nanowire transparent conductive films from the perspective of the length of nanowires for various optoelectronic applications

Silver nanowires as transparent conductive films in the near-infrared spectral range

Transparent conductive films (TCFs) comprise a crucial component of optoelectronic devices, such as displays, light-emitting diodes, solar cells and touch screens. Indium tin oxide (ITO) currently dominates among TCFs in the visible spectral range due to the high transmittance at low resistivity. However, the remarkable decrease of the transmittance in the near-infrared range (NIR) restricts from using ITO as highly efficient NIR TCF. Here we show that silver nanowires (AgNWs) possesses up to 95% transmittance for whole 0.75-2.5|jm near-infrared spectral range

Расчет оптических параметров тонких пленок конструкционных материалов теплового неохлаждаемого детектора болометрического типа

The increased interest in utilizing uncooled thermal bolometer-type detectors (microbolometers) within the infrared or terahertz detection field is justified by their operational and technological characteristics, in particular: relatively low manufacturing cost, high detection efficiency, compatibility with silicon CMOS technology, and operation at room temperature. The performance of such detectors depends on optimizing critical parameters, which are dictated by both the geometrical design and the electrical, optical, and thermal properties of the materials used. The determination of optical parameters stands as a decisive factor in the design of microbolometer structures. This article delves into the examination of optical parameters of thin films of structural materials of microbolometer based on thermosensitive vanadium oxide film manufactured at JSC “INTEGRAL”. The investigation showcases the results of determining optical constants (refractive indexes n and absorption coefficients k) of thin films from the transmission curve by applying the reflection-transmission method. Furthermore, a comparison is carried out between the results of computer modeling of the transmission, reflection and absorption spectra – taking into account the obtained values of the coefficients n and k – and the empirical data from the in-situ experiment.Повышенный интерес к применению неохлаждаемых тепловых детекторов болометрического типа (микроболометров) в инфракрасном или терагерцовом поле обнаружения обоснован их эксплуатационными и технологическими характеристиками, в частности: относительно низкой стоимостью изготовления, высокой эффективностью обнаружения, совместимостью с кремниевой КМОП-технологией, работоспособностью при комнатной температуре. Характеристики таких детекторов зависят от оптимизации критических параметров, которые определяются геометрией конструкции, а также электрическими, оптическими и тепловыми свойствами применяемых материалов. Определение оптических параметров является одним из решающих факторов при проектировании приборных структур микроболометров. В статье исследованы оптические параметры тонких пленок конструкционных материалов микроболометра на основе термочувствительной пленки оксида ванадия, изготовленных в ОАО «ИНТЕГРАЛ». Приведены результаты определения посредством применения метода отражения-передачи оптических констант (коэффициентов преломления n и поглощения k) тонких пленок по кривой пропускания. Выполнено сравнение результатов компьютерного моделирования спектров пропускания, отражения и поглощения с учетом полученных значений коэффициентов n и k с данными натурного эксперимента

Оптические, механические и электрические характеристики теплового неохлаждаемого детектора болометрического типа на основе оксида ванадия

Determination of optical, mechanical and electrical characteristics is one of the decisive factors in the design of instrumentation structures of thermal uncooled bolometer-type detectors (microbolometers). The paper presents the results of optimization calculations by means of computer simulation of absorption, transmittance and reflection spectra of device structures of microbolometers based on thermosensitive vanadium oxide film by finite-difference time-domain method (FDTD). The characteristics of the investigated microbolometer structure were checked for compliance with mechanical and electrical requirements for this class of devices.Определение оптических, механических и электрических характеристик является одним из решающих факторов при проектировании приборных структур тепловых неохлаждаемых детекторов болометрического типа (микроболометров). В статье представлены результаты оптимизационных расчетов посредством компьютерного моделирования спектров поглощения, пропускания и отражения приборных структур микроболометров на основе термочувствительной пленки оксида ванадия методом конечных разностей во временной области (англ. finite-difference time-domain, FDTD). Выполнена проверка на соответствие характеристик исследуемой структуры микроболометра механическим и электрическим требованиям, предъявляемым к данному классу приборов

Семантический анализ речевых сообщений на основе формализованного контекста

The report is devoted to the problem of using formalized contextual information for the semantic analysis of voice messages in conversational systems with a speech interface. The paper proposes an approach based on several fundamental principles: the transition from the acoustic pattern to the semantic representation bypassing a separate stage of textual presentation of information, saving and processing contextual information at all levels in a single knowledge base, transferring the linguistic processing stage to the semantic analysis block (which allows to take into account not only statistical but also semantic links at this level), of applying feedback from the semantic level to the lower level to adjust the result of links work. To implement the approach, the original signal processing technique based on instantaneous harmonic analysis, convolutional neural networks for solving the classification problem, as well as the capabilities of the OSTIS methodology and technology were used

Optical properties of thin metallic nano-patterned films for display applications

Transparent conductive films are a crucial component of many optoelectronic devices such as displays, solar cells, touch screens, and light-emitting diodes. To date, indium tin oxide (ITO) based TCFs dominate the electronics industry. But a high fabrication cost and non-flexibility of the ITO prevent its application in future generation devices. Among potential candidates such as graphene, polymers and zinc oxide, metallic nanowire and nanoporous layers demonstrate a large potential to replace the ITO. Besides low fabrication cost, flexibility and stretchability, they surpass the optoelectronic performance of ITO. Here we demonstrate silver nanowire (AgNW) and nanoporous (AgNP) layers, which possess the transmittance up to 10% higher than ITO at 20Ω/□ sheet resistance

Nanoporous gold metamaterials for high sensitivity plasmonic sensing

Surface plasmon resonance sensors are a well-established class of sensors that includes a very large variety of materials and detection schemes. However, the development of portable devices is still challenging due to the intrinsic complexity of the optical excitation/detection schemes. This work shows that nanoporous gold (NPG) films can overcome the said limitations by providing an excellent sensitivity without the need for sophisticated fabrication approaches and/or optical setups. The sensing mechanism is related to the co-localization of optical energy and analytes in the pores fostering an enhanced light-matter coupling. As a result, when molecules are adsorbed in the pores, the NPG film shows a significant spectral shift of the effective plasma frequency and an abrupt change of the reflectivity. By monitoring the reflectivity in the spectral region close to the plasma frequency (namely the plasma edge), it is possible to detect the analyte. Through a series of experiments, the authors demonstrated a sensitivity exceeding 15 000 nm per RIU in the near infrared range comparable with the state of the art of plasmonic metamaterials

Optoelectronic performance optimization for transparent conductive layers based on randomly arranged silver nanorods

Optoelectronic performance of transparent conductive layers (TCLs) based on randomly arranged silver (Ag) nanorods (NRs) is simulated. Models for calculation of optical and electronic properties were proposed founded on finite-difference time-domain method and percolation theory respectively. Obtained simulation results are well conformed to experimental data. The influence of angle deviation of NR crossings on the transmittance and sheet resistance are demonstrated. The balance between transmittance and sheet resistance which can be easily set by varying the combinations of NR radius and NR number is shown. Our results demonstrate that randomly arranged Ag layers are promising candidates for flexible TCLs