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10 pages, 2799 KiB

Open AccessArticle

Surface Modification of Heterojunction with Intrinsic Thin Layer Solar Cell Electrode with Organosilane

by Bing-Mau Chen, Chih-Hung Chen and Shang-Ping Ying

Micromachines 2024, 15(11), 1339; https://doi.org/10.3390/mi15111339 - 31 Oct 2024

Viewed by 523

Solar cell (SC) technologies, which are essential in the transition toward sustainable energy, utilize photovoltaic cells to convert solar energy into electricity. Of the available technologies, heterojunction with intrinsic thin-layer (HIT) solar cells offers high efficiency and reliability. The current study explored the [...] Read more.

Solar cell (SC) technologies, which are essential in the transition toward sustainable energy, utilize photovoltaic cells to convert solar energy into electricity. Of the available technologies, heterojunction with intrinsic thin-layer (HIT) solar cells offers high efficiency and reliability. The current study explored the enhancement of HIT solar cell performance through the use of 3-aminopropyltrimethoxysilane (APTMS) self-assembled monolayers (SAMs) on the surface of the cells’ indium tin oxide (ITO) layer. Photoluminescence mapping revealed greater brightness and photocurrent in the HIT sample treated with APTMS SAMs, with the results indicating more favorable optical and electrical properties. The application of APTMS SAMs led to higher open-circuit voltage, fill factor, maximum power output, and efficiency by passivating the ITO surface and achieving energy level alignment, thereby enhancing the charge carrier dynamics. These findings demonstrate the potential of APTMS SAMs to improve HIT solar cell efficiency and reliability. Full article

(This article belongs to the Special Issue Microelectronics and Optoelectronic Devices: From Fundamental Research to Advanced Applications)

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9 pages, 2494 KiB

Open AccessArticle

Utilization of Optical OFDM Modulation on Blue LED VLC Datacom Without Equalization for 4 m Wireless Link

by Yuan-Zeng Lin, Chien-Hung Yeh, Wen-Piao Lin and Chi-Wai Chow

Micromachines 2024, 15(11), 1322; https://doi.org/10.3390/mi15111322 - 30 Oct 2024

Viewed by 478

Abstract

To achieve higher visible light communication (VLC) traffic capacity, using the wide bandwidth light-emitting diode (LED) and spectral efficiency modulation signal, is currently the most commonly used method. In this demonstration, we apply the orthogonal frequency division multiplexing quadrature amplitude modulation (OFDM-QAM) with [...] Read more.

To achieve higher visible light communication (VLC) traffic capacity, using the wide bandwidth light-emitting diode (LED) and spectral efficiency modulation signal, is currently the most commonly used method. In this demonstration, we apply the orthogonal frequency division multiplexing quadrature amplitude modulation (OFDM-QAM) with bit- and power-loading algorithm on single blue LED to achieve >1 Gbit/s VLC capacity, when a 400 MHz bandwidth avalanche photodiode (APD)-based receiver (Rx) is exploited for decoding. Here, the higher sensitivity APD can be applied to compensate for the wireless VLC link length in the proposed LED VLC system, and due to the lower LED illumination (255 to 40 lux), is used for the indoor access network after passing the wireless link length of 1 to 4 m. As a result, using single blue LED can achieve 0.962 to 1.057 Gbit/s OFDM rate with available 400 MHz bandwidth APD in poorly illuminated condition indoors without applying analogy equalization. Full article

(This article belongs to the Special Issue Microelectronics and Optoelectronic Devices: From Fundamental Research to Advanced Applications)

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11 pages, 5162 KiB

Open AccessArticle

Thiol-SAM Concentration Effect on the Performance of Interdigitated Electrode-Based Redox-Free Biosensors

by Abdulaziz K. Assaifan

Micromachines 2024, 15(10), 1254; https://doi.org/10.3390/mi15101254 - 12 Oct 2024

Viewed by 711

Abstract

Despite the direct, redox-free and simple detection non-faradaic impedimetric biosensors offer, considerable optimizations are required to enhance their performance for the detection of various biomarkers. Non-faradaic EIS sensors’ performance depends on the interfacial capacitance between a polarized biosensor surface and the tested sample [...] Read more.

Despite the direct, redox-free and simple detection non-faradaic impedimetric biosensors offer, considerable optimizations are required to enhance their performance for the detection of various biomarkers. Non-faradaic EIS sensors’ performance depends on the interfacial capacitance between a polarized biosensor surface and the tested sample solution. Careful engineering and design of the interfacial capacitance is encouraged to magnify the redout signal upon bioreceptor–antigen interactions. One of the methods to achieve this goal is by optimizing the self-assembled monolayer concentration, which has not been reported for non-faradaic impedimetric sensors. Here, the impact of alkanethiolate (cysteamine) concentration on the performance of gold (Au) interdigitated electrode (Au-IDE) biosensors is reported. Six sets of biosensors were prepared, each with a different cysteamine concentration: 100 nM, 1 μM, 10 μM, 100 μM, 1 mM, and 10 mM. The biosensors were prepared for the direct detection of LDL cholesterol by attaching LDL antibodies on top of the cysteamine via a glutaraldehyde cross-linker. As the concentration of cysteamine increased from 100 nM to 100 μM, the sensitivity of the biosensor increased from 6.7 to 16.2 nF/ln (ng/mL). As the cysteamine concentration increased from 100 μM to 10 mM, the sensitivity deteriorated. The limit of detection (LoD) of the biosensor improved as the cysteamine increased from 100 nM to 100 μM (i.e., 400 ng/mL to 59 pg/mL). However, the LoD started to increase to 67 pg/mL and 16 ng/mL for 1 mM and 10 mM cysteamine concentrations, respectively. This shows that the cysteamine concentration has a detrimental effect on redox-free biosensors. The cysteamine layer has to be as thin as possible and uniformly cover the electrode surfaces to maximize positive readout signals and reduce negative signals, significantly improving both sensitivity and LoD. Full article

(This article belongs to the Special Issue Microelectronics and Optoelectronic Devices: From Fundamental Research to Advanced Applications)

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19 pages, 11191 KiB

Open AccessArticle

A Highly Linear Ultra-Low-Area-and-Power CMOS Voltage-Controlled Oscillator for Autonomous Microsystems

by Javier de Mena Pacheco, Tomas Palacios, Marek Hempel and Marisa Lopez Vallejo

Micromachines 2024, 15(10), 1193; https://doi.org/10.3390/mi15101193 - 26 Sep 2024

Viewed by 3317

Abstract

Voltage-controlled oscillators (VCOs) can be an excellent means of converting a magnitude into a readable value. However, their design becomes a real challenge for power-and-area-constrained applications, especially when a linear response is required. This paper presents a VCO for smart dust systems fabricated [...] Read more.

Voltage-controlled oscillators (VCOs) can be an excellent means of converting a magnitude into a readable value. However, their design becomes a real challenge for power-and-area-constrained applications, especially when a linear response is required. This paper presents a VCO for smart dust systems fabricated by 65 nm technology. It is designed to minimize leakage, limit high peak currents and provide an output whose frequency variation is linear with the input voltage, while allowing rail-to-rail input range swing. The oscillator occupies 592

μ m^{2}

, operates in a frequency range from 43 to 53 Hz and consumes a maximum average power of 210 pW at a supply voltage of 1 V and 4 pW at 0.3 V. In addition, the proposed VCO exhibits a quasi-linear response of frequency vs. supply voltage and temperature, allowing easy temperature compensation with complementary to absolute temperature (CTAT) voltage. Full article

(This article belongs to the Special Issue Microelectronics and Optoelectronic Devices: From Fundamental Research to Advanced Applications)

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10 pages, 7454 KiB

Open AccessArticle

Optical Properties and Growth Characteristics of 8-Quinolinolato Lithium (Liq) Nano-Layers Deposited by Gas Transport Deposition

by Alexandros Zachariadis, Michalis Chatzidis, Despoina Tselekidou, Olaf Wurzinger, Dietmar Keiper, Peter K. Baumann, Michael Heuken, Kyparisis Papadopoulos, Argiris Laskarakis, Stergios Logothetidis and Maria Gioti

Micromachines 2024, 15(9), 1089; https://doi.org/10.3390/mi15091089 - 28 Aug 2024

Viewed by 727

Abstract

Organometallic complexes containing reactive alkali metals, such as lithium (Li), represent a promising material approach for electron injection layers and electron transport layers (EILs and ETLs) to enhance the performance of Organic Light-Emitting Diodes (OLEDs). 8-Quinolinolato Lithium (Liq) has shown remarkable potential as [...] Read more.

Organometallic complexes containing reactive alkali metals, such as lithium (Li), represent a promising material approach for electron injection layers and electron transport layers (EILs and ETLs) to enhance the performance of Organic Light-Emitting Diodes (OLEDs). 8-Quinolinolato Lithium (Liq) has shown remarkable potential as an EIL and ETL when conveyed in very thin films. Nevertheless, the deposition of nano-layers requires precise control over both thickness and morphology. In this work, we investigate the optical properties and morphological characteristics of Liq thin films deposited via Organic Vapor Phase Deposition (OVPD). Specifically, we present our methodology for analyzing the measured pseudodielectric function <ε(ω)> using Spectroscopic Ellipsometry (SE), alongside the nano-topography of evaporated Liq nano-layers using Atomic Force Microscopy (AFM). This information can contribute to the understanding of the functionality of this material, since ultra-thin Liq interlayers can significantly increase the operational stability of OLED architectures. Full article

(This article belongs to the Special Issue Microelectronics and Optoelectronic Devices: From Fundamental Research to Advanced Applications)

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16 pages, 3805 KiB

Open AccessArticle

Machine Learning-Guided Cycle Life Prediction for Electrochromic Devices Based on Deuterium and Water Mixing Solvent

by Yitong Wu, Sifan Kong, Qingxin Yao, Muyun Li, Huayi Lai, Duoyu Sun, Qingyue Cai, Zelin Qiu, Honglong Ning and Yong Zhang

Micromachines 2024, 15(9), 1073; https://doi.org/10.3390/mi15091073 - 26 Aug 2024

Viewed by 1229

Abstract

Electrochromic devices have demonstrated considerable potential in a range of applications, including smart windows and automotive rearview mirrors. However, traditional cycle life testing methods are time-consuming and require significant resources to process a substantial amount of generated data, which presents a significant challenge [...] Read more.

Electrochromic devices have demonstrated considerable potential in a range of applications, including smart windows and automotive rearview mirrors. However, traditional cycle life testing methods are time-consuming and require significant resources to process a substantial amount of generated data, which presents a significant challenge and remains an urgent issue to be addressed. To address this challenge, we proposed the use of Long Short-Term Memory (LSTM) networks to construct a prediction model of the cycle life of electrochromic devices and introduced an interpretable analysis method to further analyze the model’s predictive capabilities. The original dataset used for modeling was derived from preliminary experiments conducted under 1000 cycles of six devices prepared with varying mixing ratios of heavy water (D₂O). Furthermore, validation experiments confirmed the feasibility of the D₂O mixing strategy, with 83% of the devices exhibiting a high initial transmittance modulation amplitude (ΔT = 43.95%), a rapid response time (t_c = 7 s and t_b = 8 s), and excellent cyclic stability (ΔT = 44.92% after 1000 cycles). This study is the first to use machine learning techniques to predict the cycle life of electrochromic devices while proposing performance enhancement and experimental time savings for inorganic all-liquid electrochromic devices. Full article

(This article belongs to the Special Issue Microelectronics and Optoelectronic Devices: From Fundamental Research to Advanced Applications)

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11 pages, 5108 KiB

Open AccessArticle

A Low-Power Optoelectronic Receiver IC for Short-Range LiDAR Sensors in 180 nm CMOS

by Shinhae Choi, Yeojin Chon and Sung Min Park

Micromachines 2024, 15(9), 1066; https://doi.org/10.3390/mi15091066 - 23 Aug 2024

Viewed by 803

Abstract

This paper presents a novel power-efficient topology for receivers in short-range LiDAR sensors. Conventionally, LiDAR sensors exploit complex time-to-digital converters (TDCs) for time-of-flight (ToF) distance measurements, thereby frequently leading to intricate circuit designs and persistent walk error issues. However, this work features a [...] Read more.

This paper presents a novel power-efficient topology for receivers in short-range LiDAR sensors. Conventionally, LiDAR sensors exploit complex time-to-digital converters (TDCs) for time-of-flight (ToF) distance measurements, thereby frequently leading to intricate circuit designs and persistent walk error issues. However, this work features a fully differential trans-impedance amplifier with on-chip avalanche photodiodes as optical detectors so that the need of the following post-amplifiers and output buffers can be eliminated, thus considerably reducing power consumption. Also, the combination of amplitude-to-voltage (A2V) and time-to-voltage (T2V) converters are exploited to replace the complicated TDC circuit. The A2V converter efficiently processes weak input photocurrents ranging from 1 to 50 μA_pp which corresponds to a maximum distance of 22.8 m, while the T2V converter handles relatively larger photocurrents from 40 μA_pp to 5.8 mA_pp for distances as short as 30 cm. The post-layout simulations confirm that the proposed LiDAR receiver can detect optical pulses over the range of 0.3 to 22.8 m with a low power dissipation of 10 mW from a single 1.8 V supply. This topology offers significant improvements in simplifying the receiver design and reducing the power consumption, providing a more efficient and accurate solution that is highly suitable for short-range LiDAR sensor applications. Full article

(This article belongs to the Special Issue Microelectronics and Optoelectronic Devices: From Fundamental Research to Advanced Applications)

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17 pages, 4721 KiB

Open AccessArticle

A Microwave Photonic 2 × 2 IBFD–MIMO Communication System with Narrowband Self-Interference Cancellation

by Ying Ma, Fangjing Shi and Yangyu Fan

Micromachines 2024, 15(5), 593; https://doi.org/10.3390/mi15050593 - 29 Apr 2024

Viewed by 1082

Abstract

Combined in-band full duplex-multiple input multiple output (IBFD–MIMO) technology can significantly improve spectrum efficiency and data throughput, and has broad application prospects in communications, radar, the Internet of Things (IoT), and other fields. Targeting the self-interference (SI) issue in microwave photonic-based IBFD–MIMO communication [...] Read more.

Combined in-band full duplex-multiple input multiple output (IBFD–MIMO) technology can significantly improve spectrum efficiency and data throughput, and has broad application prospects in communications, radar, the Internet of Things (IoT), and other fields. Targeting the self-interference (SI) issue in microwave photonic-based IBFD–MIMO communication systems, a microwave photonic self-interference cancellation (SIC) method applied to the narrowband 2 × 2 IBFD–MIMO communication system was proposed, simulated, and analyzed. An interleaver was used to construct a polarization multiplexing dual optical frequency comb with a frequency shifting effect, generating a dual-channel reference interference signal. The programmable spectrum processor was employed for filtering, attenuation, and phase-shifting operations, ensuring amplitude and phase matching to eliminate the two self-interference (SI) signals. The simulation results show that the single-frequency SIC depth exceeds 45.8 dB, and the narrowband SIC depth under 30 MHz bandwidth exceeds 32.7 dB. After SIC, the desired signal, employing a 4QAM modulation format, can be demodulated with an error vector magnitude (EVM) as low as 4.7%. Additionally, further channel expansion and system performance optimization are prospected. Full article

(This article belongs to the Special Issue Microelectronics and Optoelectronic Devices: From Fundamental Research to Advanced Applications)

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15 pages, 6041 KiB

Open AccessArticle

Theoretical Justification of Structural, Magnetoelectronic and Optical Properties in QFeO₃ (Q = Bi, P, Sb): A First-Principles Study

by Amna Parveen, Zeesham Abbas, Sajjad Hussain, Shoyebmohamad F. Shaikh, Muhammad Aslam and Jongwan Jung

Micromachines 2023, 14(12), 2251; https://doi.org/10.3390/mi14122251 - 17 Dec 2023

Cited by 9 | Viewed by 1215

Abstract

One of the primary objectives of scientific research is to create state-of-the-art multiferroic (MF) materials that exhibit interconnected properties, such as piezoelectricity, magnetoelectricity, and magnetostriction, and remain functional under normal ambient temperature conditions. In this study, we employed first-principles calculations to investigate how [...] Read more.

One of the primary objectives of scientific research is to create state-of-the-art multiferroic (MF) materials that exhibit interconnected properties, such as piezoelectricity, magnetoelectricity, and magnetostriction, and remain functional under normal ambient temperature conditions. In this study, we employed first-principles calculations to investigate how changing pnictogen elements affect the structural, electronic, magnetic, and optical characteristics of QFeO₃ (Q = Bi, P, SB). Electronic band structures reveal that BiFeO₃ is a semiconductor compound; however, PFeO₃ and SbFeO₃ are metallic. The studied compounds are promising for spintronics, as they exhibit excellent magnetic properties. The calculated magnetic moments decreased as we replaced Bi with SB and P in BiFeO₃. A red shift in the values of

ε_{2} (ω)

was evident from the presented spectra as we substituted Bi with Sb and P in BiFeO₃. QFeO₃ (Q = Bi, P, SB) showed the maximum absorption of incident photons in the visible region. The results obtained from calculating the optical parameters suggest that these materials have a strong potential to be used in photovoltaic applications. Full article

(This article belongs to the Special Issue Microelectronics and Optoelectronic Devices: From Fundamental Research to Advanced Applications)

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