Thin Devices Research Articles

Highly sensitive detection of malaria biomarker through matching channel and gate capacitance of integrated organic electrochemical transistors

Organic electrochemical transistors (OECTs) possess versatile advantages for biochemical and electrophysiological applications due to electrochemical gating and ion-to-electron conversion capability. Although OECTs have been successfully applied for biochemical sensing, the effect of relative capacitance for specific sensing events is still unclear. In the present work, we design integrated interdigitated OECTs (iOECTs) with on-plane gold gate and different channel geometries for point-of-care diagnosis of malaria using aptamer as receptor. The transconductance of the iOECTs gated with micro-size gold electrodes decreased with increasing the channel thicknesses, especially for devices with large channel areas, which is inconsistent with devices gated by typical Ag/AgCl electrodes, attributing to the limited gating efficiency of the micro-size gate electrode. The capacitance of gate electrode was heavily suppressed by receptors but increased with the incubation of targets. In addition, the integrated iOECTs with thin channels exhibited superior sensitivity for malaria detection with the detection limit as low as 3.2 aM, much lower than their thick channel counterpart and other state-of-the-art biosensors. These deviations could be caused by the high relative capacitances, with respect to the gate and channel capacitance (Cg/Cch), resulting in a high gate potential drop over the organic channel and thus entirely gating on the thin channel device. These findings provide guidance to optimize the geometry of OECT devices with on-chip integrated gates and the fabrication of miniaturized OECTs for biosensing applications.

Spatiotemporally Controllable Chemical Delivery Utilizing Electroosmotic Flow Generated in Combination of Anionic and Cationic Hydrogels

AbstractSpatiotemporally controlled chemical delivery is crucial for various biomedical engineering applications. Here, a novel concept of electrically controllable delivery utilizing electroosmotic flow (EOF) generated in a combination of anionic and cationic hydrogels (A‐ and C‐hydrogels) is reported. The unique advantages of the A/C‐hydrogel combination are demonstrated utilizing a flexible sheet‐shaped and a thin tubular devices. Since the directions of EOF in the A‐ and C‐hydrogels are opposite to each other, the ionic current for EOF generation flows inside the delivery devices, enabling chemical delivery without accompanying external ionic current that could stimulate target cells and tissues. A thin tubular device, which can be inserted into narrow in vivo structures and be integrated with other flexible devices, exhibits high robustness and repeatability thanks to the flexibility and water retentivity of hydrogels. The EOF devices with A/C‐hydrogels combination show high controllability superior to the pumping with a conventional syringe; the volumetric flow rate is able to be controlled proportionally to the current applied, for example, ≈0.4 µL (mA min)−1 for the tubular device. The developed EOF‐based devices are versatile for delivery of most chemicals regardless of their charge and size, and have great potential for both biomedical researches and therapeutics.

Gate-assisted MoSe2 transistor to detect the streptavidin via supporter molecule engineering

Atomically thin two-dimensional (2D) transition metal dichalcogenide (TMDC) semiconductor materials have garnered significant attention due to their remarkable properties surpassing conventional metal-oxide semiconductors. These properties include high carrier mobility, adjustable bandgaps, and exceptional sensitivity, providing them with tremendous potential for various applications. The remarkable characteristics of these 2D semiconductor materials led to fabricating of atomically thin electronic devices including diodes, photodetectors, memristors, and biosensors. Here, we present an atomically thin transistor composed of n-type molybdenum di-selenide (n-MoSe2), exhibiting a large reverse current. The charge transport through the MoSe2 transistor is modulated via back gate voltage, studied at various basing and gate voltages. Finally, the MoSe2 transistor device is utilized as a biosensor to detect the protein (streptavidin) as target analyte at fixed biasing and gate voltages. Using our designed pyrene-based supporter molecule, which is stacked over the MoSe2 surface via π-π stacking, the target protein is identified while avoiding any screening effects like Debye screening. Additionally, the real-time response of the biosensing device is recorded while maintaining a constant biasing voltage of 0.5 V, covering a range of streptavidin concentrations down to the lowest detectable concentration of 1 pM. Such utilization of the MoSe2 device as a biosensor could pave the way for manufacturing cutting-edge electrical devices which can detect a broad range of biomolecules, such as DNA (like ct-DNA) and the COVID-19 spike protein.

Boron sub-phthalocyanine chloride deposited on PA substrate towards flexible optoelectronic devices: Structural, optical, and electrical characterization

Flexible thin film photovoltaic devices have been a way of interest for researchers through the last decade. Creating suitable ultrathin films of any material is necessary for the realization of flexible systems. Therefore, the current study aims to study the impact of the thickness of the Boron sub-phthalocyanine chloride B(SubPc)Cl deposited on flexible Polyacetate (PA) as a polymer substrate. The structural properties of B(SubPc)Cl/PA with different thicknesses have been investigated using XRD and AFM. The investigated samples show an amorphous characterization with grain size slightly changed from 107 to 131 nm for thicknesses of 76 and 300 nm respectively, which is affected by the effect of the thickness. The optical transmission and absorption were studied in the spectral range of 300–2500 nm where the characteristic bands of a metallic phthalocyanine known as B and Q bands were observed in this range of the spectrum. The dispersion parameters, optical dielectric, SELF, and VELF for B(SubPc)Cl/PA were calculated and interpreted. Also, by using Tauc's extrapolation, the optical energy gap (Eg) was calculated. The Eg has values of 1.76 and 3.19 for a thickness of 76 nm which increased by increasing the film thickness. The nonlinear optical properties of B(SubPc)Cl/PA have been investigated, and the values obtained showed a high nonlinear optical response. The research outcomes candidate B(SubPc)Cl/PA for optoelectronics applications such as solar cells, sensors, and nonlinear optical devices.

Opto-iontronic coupling in triboelectric nanogenerator

Triboelectric nanogenerator (TENG) has received tremendous attentions for its ability to convert mechanical energy into electrical energy. However, the induced current generated by TENG is an alternating-current (AC) signal and cannot directly satisfy most electronic devices that require direct-current (DC) supply. As a result, there has been a great number of interests in developing DC-TENG. Here, we have successfully developed an alternative to rectify TENG for DC output by coupling the electronic displacement current of TENG with ionic current, which could be further replenished by photocurrent. For the first time, an opto-iontronic current coupling in TENG was achieved under UV irradiation. A photogenerated electric field is triggered to remotely manipulate ion migration to complement the dissipation of ion concentration gradient. This permits the ionic current to be continually generated to rectify the electronic displacement current from the TENG in the opposite direction, while allowing coupling of both ionic and electronic current in the same direction. The opto-iontronic DC-TENG could be fabricated into one integrated flexible and thin device and the ionic charge could be remotely replenished by UV light. This study introduces a rectification paradigm for TENG and provides an effective method for in-situ AC-DC conversion, which could be potentially applied in wearable devices, bioelectronics, and self-powered intelligent sensors.

Flexible energy storage patch based on NiPS3/graphene zinc-ion hybrid supercapacitor for integrated biosensors

The rapidly developing self-powered biosensor technologies require flexible, robust, and safe energy storage devices. One of the key factors of a self-powered system is the integration of energy storage device components with bio-sensors. Here, we developed a hybrid self-powered biosensor system for health monitoring comprising zinc-ion supercapacitor (ZISC) wearable patch, introducing a two-dimensional (2D) NiPS3 as a metal phosphorus chalcogenide capacitive electrode. Due to its inherent 2D nanosheet morphology, NiPS3 electrode confined with graphene (NiPS3@graphene) shows good electrochemical performance. The ZISC printed with NiPS3@graphene and zinc on cellulose substrate followed by hydrogel electrolyte results in a powerful, robust, and flexible device. It exhibits stable energy storage performance, retaining 86% capacity after 1000 charge–discharge cycles and good mechanical flexibility at different bending angles, with a retaining capacity of 97.7% compared to initial performance after 500 bending cycles. Finally, a self-powered biosensor was developed by transforming a thin and lightweight ZISC tandem device on a medical-grade cellulose patch. This patch is demonstrated to power a wearable temperature sensor with a connection via a Bluetooth module and stationary glucose sensor to establish real-time health monitoring. Our results show the significance of 2D NiPS3@graphene-based zinc-ion supercapacitors in an application as an integrated patch for powering health monitoring systems.

Layered Low-Dimensional Ruddlesden-Popper and Dion-Jacobson Perovskites: From Material Properties to Photovoltaic Device Performance.

Layered low-dimensional halide perovskites (LDPs) with multiple quantum well structure have shown increasing research interest in photovoltaic solar cell applications owing to their intrinsic moisture stability and favorable photophysical properties in comparison with their three-dimensional (3D) counterparts. The most common LDPs are Ruddlesden-Popper (RP) phases and Dion-Jacobson (DJ) phases, both of which have made significant research advances in efficiency and stability. However, distinct interlayer cations between RP and DJ phase lead to disparate chemical bonds and different perovskite structures, which endow RP and DJ perovskite with distinctive chemical and physical properties. Plenty of reviews have reported the research progress of LDPs but no summary has elaborated from the perspective of the merits and drawbacks of the RP and DJ phases. Herein, in this review, we offer a comprehensive expound on the merits and promises of RP and DJ LDPs from their chemical structure, physicochemical properties, and photovoltaic performance research progress aiming to provide a new insight into the dominance of RP and DJ phases. Then, we reviewed the recent progress on the synthesis and implementation of RP and DJ LDPs thin films and devices, as well as their optoelectronic properties. Finally, we discussed the possible strategies to resolve existing toughs to realize the desired high-performance LDPs solar cells.

Improvement in conductivity of lead-free CH3NH3SnI3 perovskite thin film using multi-walled carbon nanotubes as a transporter

CH3NH3SnI3 is a lead-free perovskite material that gains significant attention due to its favourable properties for optoelectronic device applications. It is a potential replacement for lead-based perovskite materials. However, the presence of traps, defects, and oxidation vacancies within these perovskite-based devices hinders the flow of charge carriers, causing them to become trapped or recombined within the device before reaching the electrodes. This limits the electrical performance of the device. To address this issue, this study focuses on improving the electrical performance of CH3NH3SnI3 perovskite by incorporating MWCNTs. Thin films of CH3NH3SnI3 perovskite were prepared both with and without MWCNTs. By employing the Van der Pauw method, resistivity measurements revealed that the electrical conductivity of the film increased to 7.80 × 10−2 S/m with the presence of MWCNTs, compared to 8.4 × 10−4 S/m without them. I-V measurements of the thin films-based Schottky devices showed that the conductivity increased from 1.21 × 10−5 S/m to 1.02 × 10−4 S/m with MWCNTs, while the barrier height decreased from 0.51 eV to 0.43 eV, and the ideality factor decreased from 4.01 to 2.56. The improved electrical performance observed when MWCNTs were incorporated, suggested that they formed a charge transfer pathway for carriers within the perovskite material. This pathway reduced trap energy, enabling charge carriers to percolate between grains and reach the electrodes. These findings highlight the significance of MWCNTs as a means to enhance the charge transfer dynamics in environmentally friendly CH3NH3SnI3 perovskite-based devices. Such improvements have promising implications for the development of future perovskite-based devices.

Novel SHAL base derived cobalt containing organic semiconducting metallogel thin film for self-powered high-performance photodetector application

The development of new materials with facile synthesis and better semiconducting and photonic properties is crucial for the fabrication of durable thin film-based semiconductor devices. In this study, an organic semiconducting and photo-conducting metallogel has been obtained by deprotonation of the ligand SHAL using LiOH followed by treatment with Co(II) acetate in dimethylformamide (DMF) under ambient conditions. Various characterization techniques are used to analyze the mechanical, morphological, and optical properties. This analyses reveal the formation of a organic semiconducting Co(II)-metallogel with a nanofibrous architecture. Furthermore, a comprehensive analysis of this material in thin film form demonstrates its n-type organic semiconducting nature with a good rectification ratio in the Schottky diode configuration, among the best-known values of all these materials. The Co(II)-metallogel is analyzed based on its semiconducting properties as a self-powered (in absence of external bias voltage) photodetectors (PDs) in an ITO/Co(II)-metalogel/Au configuration, for the first time. The measured photocurrent demonstrates responsivity, R(λ), of 2.77 x 103, 0.27 x 103, and 0.025 × 103 mA/W, external quantum efficiency (EQE) of 73.4 x 104, 63.1 x 103, and 25 x 103, and detectivity (D) of 5.28 x 1012, 5.2 x 1011, 4.7 x 109 Jones, with on/off ratio of 16 080, 1580, and 150 at 0 V under the illumination of 470-nm (blue), 530-nm (green), and 630-nm (red) light sources, respectively. The high performance of the PDs is attributed to the UV–vis spectrum of the thin film, morphology, and metal-semiconductor energy band schematic outcomes. Overall, this study presents considerable potential for novel applications of Co(II)metallogels in technologically challenging electronic and optoelectronic devices.

Development of a Flexible Thin Wearable Device for Tuning Temperature, Humidity, and Surface Friction on Its Surface

This study proposes a wearable device that adapts its surface conditions to maximize user comfort using novel strategies to change its temperature, humidity, and friction. The device consists of three functional units, namely heating, liquid injection, and dry-air blowing units, composed of flexible materials and thin structures. Owing to its flexibility and thickness, it can be installed on garments. The surface conditions change according to the collaborative actions of the three functional units. The temperature is increased using the heating unit and decreased using both the liquid-injection and dry-air blowing units. Humidity is increased and decreased by the liquid-injection and dry-air blowing units, respectively. Finally, the friction of the contact surface area of the device with human skin is increased and decreased using the liquid-injection and dry-air blowing units, respectively. These methodologies are experimentally validated under different environmental conditions. The validation reveals that the injection of a liquid (deionized water) increases surface friction, whereas blowing air decreases friction; in particular, the presence of granular objects is effective at reducing friction. In addition, the environmental conditions of temperature and humidity influence the degree of increase or decrease, primarily because the amount of water is varied to change the humidity, lower the temperature, and increase friction: vaporization heating lowered temperature and adhesion force of water increased friction. The temperature, humidity, and kinetic friction of the wearable device range from −2.6 to +5.0 °C, −19% to +12%, and −73% to +45%, respectively.

Advances in Flexible Thermoelectric Materials and Devices Fabricated by Magnetron Sputtering

Due to the direct conversion between thermal and electrical energy, thermoelectric materials and their devices exhibit great potential for power generation and refrigeration. With the rapid development of personal wearable electronics, the design of flexible inorganic thermoelectric materials and devices receives increasing attention. As one of the most mature thin‐film fabrication techniques, magnetron sputtering plays a key role in the fabrication of inorganic thermoelectric thin films and devices, but its progress is still not timely and comprehensively reviewed. Herein, recent advances in magnetron sputtering‐fabricated thermoelectric materials and devices are studied, including their thermoelectric properties, mechanical properties, and device design routes. The differences in the properties of thermoelectric materials under different sputtering conditions, as well as their underlying mechanisms, are carefully discussed. In the end, it is pointed out the challenges and future directions for magnetron sputtering‐prepared inorganic thermoelectric thin‐film materials and devices for practical applications. This review can serve as a useful reference to guide the design of inorganic thermoelectric materials and devices prepared by magnetron‐sputtering‐based deposition techniques.

Characterizing the Influence of Charge Extraction Layers on the Performance of Triple‐Cation Perovskite Solar Cells

AbstractSelecting suitable charge transport layers and suppressing non‐radiative recombination at interfaces with the absorber layer is vital for maximizing the efficiency of halide perovskite solar cells. In this study, high‐quality perovskite thin films and devices are fabricated with different fullerene‐based electron transport layers and different self‐assembled monolayers as hole transport layers. Then, a comparative study of a significant variety of different electrical, optical, and photoemission‐based characterization techniques is performed to quantify the properties of the solar cells, individual layers, and, importantly, the interfaces between them. In addition, the limitations and problems of the different measurements, the insights gained by combining different methods, and the different strategies for extracting information from the experimental raw data, are highlighted.

Remarkable average thermoelectric performance of the highly oriented Bi(Te, Se)-based thin films and devices

Bi(Te, Se)-based compounds have attracted lots of attention for nearly two centuries as one of the most successful commercial thermoelectric (TE) materials due to their high performance at near room temperature. Compared with 3D bulks, 2D thin films are more compatible with modern semiconductor technology and have unique advantages in the construction of micro- and nano-devices. For device applications, high average TE performance over the entire operating temperature range is critical. Herein, highly c-axis-oriented N-type Bi(Te, Se) epitaxial thin films have been successfully prepared using the pulsed laser deposition technology by adjusting the deposition temperature. The film deposited at ∼260 °C demonstrate a remarkable average power factor (PFave) of ∼24.4 μW·cm−1·K−2 over the temperature range of 305–470 K, higher than most of the state-of-the-art Bi(Te, Se)-based films. Moreover, the estimated average zT value of the film is as high as ∼0.81. We then constructed thin-film TE devices by using the above oriented Bi(Te, Se) films, and the maximum output power density of the device can reach up to ∼30.1 W/m2 under the temperature difference of 40 K. Predictably, the outstanding average TE performance of the highly oriented Bi(Te, Se) thin films will have an excellent panorama of applications in semiconductor cooling and power generation.

One-step Spray coating CsPbBr3 film for planar photodetector applications

Metal halide perovskite, a promising semiconductor material, is suitable for new generation optoelectronic application. In comparison to organic -inorganic hybrid perovskites (OIHP), all inorganic CsPbX3 (X = Cl, Br and I) show superior thermal and chemical stability. Although there are many kinds of coating procedures for producing perovskite QDs peorovskite film, most studies of CsPbX3 perovskite thin film fabrication focus on solution processing techniques such as spin coating. Unfortunately, the CsPbBr3 precusor dissolubility is very low compared to OIHP, resulting in a low materials utilization and poor uniformity for the large-scale area. In this work, we report a facile spray coating method to produce CsPbBr3 film on pre-patterned Pt electrode for photodetector (PD) application. The spray-coated perovskite was demonstrated suitable for photodiode application with numbers figure of merit such as: A high responsivity of 60 A/W, high detectivity of 6× 10-13 Jones, the response time (rising and fall time) below 17 ms were obtained at 1 V under 405 nm illumination. From this study, we belive that the spray deposition technique will benefit for futher thin film-based perovskite optoelectronic devices.

Exploring the effects of substrate and substrate temperature on the properties of radio frequency magnetron sputtered ZnO thin films

The physical and optical properties of zinc oxide thin films strongly depend on the film deposition techniques. In this work, RF magnetron sputtering was used to deposit ZnO thin films on various substrates (glass, quartz, ITO-coated glass, FTO-coated glass, Si(100), Si(100)/ SiO2) to study the role of substrate and substrate temperature on the morphological, structural and optical properties of the film grown. A detailed discussion on various aspects like surface morphology, strain, photoluminescence, bandgap, surface roughness, and material composition has been done. Compressive stress was present in the films created at room temperature and differed for various substrates based on the lattice mismatch. The nature and temperature of the substrate are found to affect the surface topography of films. Substrate and substrate temperature influenced the emission characteristics of ZnO thin films. In oxygen-rich substrates, defect emissions differed. We found that quartz is a better substrate to fabricate ZnO at room temperature and both Si and Si/SiO2 are preferable at high temperatures due to the lower lattice mismatch and thermal expansion coefficient. Comparing the electrical characteristics of ZnO thin films grown on glass and quartz substrates, ZnO on glass exhibited lower resistivity and higher carrier concentration. The Triboelectric nanogenerator (TENG) combining ZnO and PDMS, was developed to operate in vertical contact-separation mode. The obtained open circuit voltage was 30 V and 33 V for ZnO grown over ITO and FTO respectively, and the slight increase is due to the rougher film's surface on FTO than ITO. The selection of substrate is crucial in many applications and our findings provide an overview of the suitability of substrate and substrate temperature for the fabrication of ZnO thin film-based optoelectronic devices.

How to GIWAXS: Grazing Incidence Wide Angle X‐Ray Scattering Applied to Metal Halide Perovskite Thin Films

AbstractThe frequency of reports utilizing synchrotron‐based grazing incident wide angle X‐ray scattering (GIWAXS) to study metal halide perovskite thin films has exploded recently, as this technique has proven invaluable for understanding several structure‐property relationships that fundamentally limit optoelectronic performance. The GIWAXS geometry and temporal resolution are also inherently compatible with in situ and operando setups (including ISOS protocols), and a relatively large halide perovskite research community has deployed GIWAXS to unravel important kinetic and dynamic features in these materials. Considering its rising popularity, the aim here is to accelerate the required learning curve for new experimentalists by clearly detailing the underlying analytical concepts which can be leveraged to maximize GIWAXS studies of polycrystalline thin films and devices. Motivated by the vast range of measurement conditions offered, together with the wide variety of compositions and structural motifs available (i.e., from single‐crystal and polycrystalline systems, to quantum dots and layered superlatices), a comprehensive framework for conducting effective GIWAXS experiments is outlined for different purposes. It is anticipated that providing a clear perspective for this topic will help elevate the quality of future GIWAXS studies—which have become routine—and provide the impetus required to develop novel GIWAXS approaches to resolve unsettled scientific questions.

Manganese-substituted kesterite thin-films for earth-abundant photovoltaic applications

Thin film photovoltaic devices based on CdTe and Cu(In,Ga)Se2 find in Cu2ZnSn(S,Se)4-based technology a more eco-friendly alternative. To further reduce production costs and improve sustainability, other abundant metals, such as manganese, can be tested as a potential alternative to zinc. Mn is a safe and Earth-abundant element, and it can be used in light absorber materials when it is part of quaternary chalcogenides with copper and tin. This work reports on the growth and characterization of Cu2MnSnS4 thin films produced by a two-step deposition process. The metallic precursors have been deposited by sputtering and the stack annealed at high temperatures in sulphur atmosphere. The layers, obtained in Cu-poor Mn-poor compositional regime, have been tested in solar devices with a record efficiency of 1.13% and a high open-circuit voltage of about 445 mV delivered by the champion device after over one year from the first PV measurement. X-ray diffraction and X-ray photoelectron, Raman, photoluminescence, and admittance spectroscopies have been used to investigate the Cu2MnSnS4 defectivity, and a scenario of high defects has emerged. Therefore, to promote the development of Mn-based photovoltaics the synthesis methodology should be optimized and the device architecture should be specifically designed for the compound.

Enhancement of Silicon Critical Breakdown Field by Reducing the Avalanche Breakdown Distance to Improve the Breakdown Voltage of Thin SOI Device

Enhancement of Silicon Critical Breakdown Field by Reducing the Avalanche Breakdown Distance to Improve the Breakdown Voltage of Thin SOI Device

Spin–orbit effects on the electronic and optical properties of lead iodide

Lead iodide (PbI2) has gained much interest due to its direct electronic gap in the visible range and layered crystal structure. It has thereby been considered as a promising material for applications in atomically thin optoelectronic devices. In this work, we present a detailed investigation of the effect of spin–orbit coupling (SOC) that arises from the presence of heavy atoms on the electronic and optical properties of PbI2 using first-principles calculations based on density-functional theory and many-body perturbation theory. We find that SOC not only alters the bandgap but also induces the mixing of orbital characters, resulting in a significant change in the overall band structure and charge carrier effective masses. Moreover, the band orbital mixing caused by SOC results in the dramatic change in optical transition matrix elements and, correspondingly, the absorption spectrum. Our experimentally measured absorption spectra validate the calculation results and demonstrate the importance of SOC in the optical processes of PbI2. Our findings provide insights that are important for the potential use of PbI2 as a material platform for visible optoelectronic devices.

Gate-Tunable Multiband Transport in ZrTe5 Thin Devices.

Interest in ZrTe5 has been reinvigorated in recent years owing to its potential for hosting versatile topological electronic states and intriguing experimental discoveries. However, the mechanism of many of its unusual transport behaviors remains controversial: for example, the characteristic peak in the temperature-dependent resistivity and the anomalous Hall effect. Here, through employing a clean dry-transfer fabrication method in an inert environment, we successfully obtain high-quality ZrTe5 thin devices that exhibit clear dual-gate tunability and ambipolar field effects. Such devices allow us to systematically study the resistance peak as well as the Hall effect at various doping densities and temperatures, revealing the contribution from electron-hole asymmetry and multiple-carrier transport. By comparing with theoretical calculations, we suggest a simplified semiclassical two-band model to explain the experimental observations. Our work helps to resolve the longstanding puzzles on ZrTe5 and could potentially pave the way for realizing novel topological states in the two-dimensional limit.