Improved Device Performance Research Articles

Carbon-based photoelectrochemical sensors: recent developments and future prospects.

Owing to the considerable potential of photoelectrochemical (PEC) sensors, they have gained significant attention in the analysis of biological, environmental, and food markers. However, the limited charge mass transfer efficiency and rapid recombination of electron hole pairs have become obstacles in the development of PEC sensors. In this case, considering the unique advantages of carbon-based materials, they can be used as photosensitizers, supporting materials and conductive substrates and coupled with semiconductors to prepare composite materials, solving the above problems. In addition, there are many types of carbon materials, which can have semiconductor properties and form heterojunctions after coupling with semiconductors, effectively promoting the separation of electron hole pairs. Herein, we aimed to provide a comprehensive analysis of reports on carbon-based PEC sensors by introducing their research and application status and discussing future development trends in this field. In particular, the types and performance improvement strategies of carbon-based electrodes and the working principles of carbon-based PEC sensors are explained. Furthermore, the applications of carbon-based photoelectric sensors in environmental monitoring, biomedicine, and food detection are highlighted. Finally, the current limitations in the research on carbon-based PEC sensors are emphasized and the need to enhance the sensitivity and selectivity through material modification, structural design, improved device performance, and other strategies are emphasized.

Asymmetric contact-induced selective doping of CVD-grown bilayer WS2 and its application in high-performance photodetection with an ultralow dark current.

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are excellent candidates for high-performance optoelectronics due to their high carrier mobility, air stability and strong optical absorption. However, photodetectors made with monolayer TMDs often exhibit a high dark current, and thus, there is a scope for further improvement. Herein, we developed a 2D bilayer tungsten disulfide (WS2) based photodetector (PD) with asymmetric contacts that exhibits an exceptionally low dark current and high specific detectivity. High-quality and large-area monolayer and bilayer WS2 flakes were synthesized using a thermal chemical vapor deposition system. Compared to conventional symmetric contact electrodes, utilizing metal electrodes with higher and lower work functions relative to bilayer WS2 aids in achieving asymmetric lateral doping in the WS2 flakes. This doping asymmetry was confirmed through the photoluminescence spectral profile and Raman mapping analysis. With the asymmetric contacts on bilayer WS2, we find evidence of selective doping of electrons and holes near the Ti and Au contacts, respectively, while the WS2 region away from the contacts remains intrinsic. When compared with the symmetric contact case, the dark current in the WS2 PD with asymmetric (Au, Ti) contact decreases by an order of magnitude under reverse bias with a concomitant increase in the photocurrent, resulting in an improved on/off ratio of ∼105 and overall improved device performance under identical illumination conditions. We explained this improved performance based on the energy band alignment showing a unidirectional charge flow under light illumination. Our results indicate that the planar device structure and compatibility with current nanofabrication technologies can facilitate its integration into advanced chips for futuristic low-power optoelectronic and nanophotonic applications.

Visible-ultraviolet dual-band photodetectors based on an all-inorganic CsPbCl3/p-GaN heterostructure.

All-inorganic metal halide perovskites (MHPs) have attracted increasing attention because of their high thermal stability and band gap tunability. Among them, CsPbCl3 is considered a promising semiconductor material for visible-ultraviolet dual-band photodetectors because of its excellent photoelectric properties and suitable band gap value. In this work, we fabricated a visible-ultraviolet dual-band photodetector based on a CsPbCl3/p-GaN heterojunction using the spin coating method. The formation of the heterojunction enables the device to exhibit obvious dual-band response behavior at positive and negative bias voltages. At the same time, the dark current of the device can be as low as 2.42 × 10-9 A, and the corresponding detection rate can reach 5.82 × 1010 Jones. In addition, through simulation calculations, it was found that the heterojunction has a type II energy band arrangement, and the heterojunction response band light absorption is significantly enhanced. The type II energy band arrangement will separate electron-hole pairs more effectively, which will help improve device performance. The successful implementation of visible-ultraviolet dual-band photodetectors based on a CsPbCl3/p-GaN heterojunction provides guidance for the application of all-inorganic MHPs in the field of multi-band photodetectors.

Efficient inverted perovskite solar cells with a low-temperature processed NiOx/SAM hole transport layer

Within this paper, the roles of MeO-2PACz in improving device performance were investigated. Afterwards, the NiOx prepared at low temperature is introduced to improve the coverage of SAM, further optimizing the energy level alignment and passivating defects.

Properties and Emerging Applications of Ruthenium Nanoclusters

Abstract Ruthenium nanoclusters have shown great promise as multifunctional nanomaterials in broad scientific and technological sectors. Owing to their distinct characteristics arising from their nanoscale size and tunable electrical configuration, ruthenium nanoclusters are highly useful in photocatalysis, biomedical, electronics, sensors, and energy storage applications. Ruthenium nanoclusters are an effective catalyst with remarkable activity and selectivity. Contact with reactants is facilitated by their large surface area. Size-dependent electronic characteristics enable ruthenium nanoclusters to detect gases and biomolecules with high sensitivity and selectivity. The creation of sophisticated materials for electronic devices, such as transistors, memory chips, and conductive coatings, is facilitated by ruthenium nanoclusters. These materials’ distinct electronic structures enable more effective and flexible electronic systems, and consequently improve device performance. Because of their stability and biocompatibility, ruthenium nanoclusters are used in the biomedical industry as drug delivery systems and imaging agents. Finally, ruthenium nanoclusters have shown photocatalytic efficiency in light-driven chemical processes, and thus may aid in solar energy conversion and environmental cleanup. Their roles in sustainable uses of solar energy may make these materials valuable for solving global problems.

Conjugated D–π–A photovoltaic polymers containing thieno[3,2-b]thiophene π-bridge

We review the development of TT-bridged D–π–A copolymers and emphasize the role played by TT-bridge on tuning polymer properties and improving device performance.

Highly efficient iridium(iii) phosphors with a 2-(4-benzylphenyl)pyridine-type ligand and their high-performance organic light-emitting diodes

Benzyl-modified iridium(iii)-ppy electrophosphors (Hppy = 2-phenylpyridine) are synthesized and characterized. They show much improved device performance as compared to the benchmark green emitters fac-Ir(ppy)3 and Ir(ppy)2(acac) in OLEDs.

Recent advances in flexible memristors for advanced computing and sensing.

Conventional computing systems based on von Neumann architecture face challenges such as high power consumption and limited data processing capability. Improving device performance via scaling guided by Moore's Law becomes increasingly difficult. Emerging memristors can provide a promising solution for achieving high-performance computing systems with low power consumption. In particular, the development of flexible memristors is an important topic for wearable electronics, which can lead to intelligent systems in daily life with high computing capacity and efficiency. Here, recent advances in flexible memristors are reviewed, from operating mechanisms and typical materials to representative applications. Potential directions and challenges for future study in this area are also discussed.

Improving the performance of kesterite solar cells by solution germanium alloying.

Cation substitution is an effective strategy to regulate the defects/electronic properties of kesterite Cu2ZnSn(S,Se)4 (CZTSSe) absorbers and improve the device photovoltaic performance. Here, we report Ge alloying kesterite Cu2Zn(Sn,Ge)(S,Se)4 (CZTGSSe) via a solution approach. The results demonstrate that the same chemical reaction of Ge4+ to Sn4+ ensures homogeneous Ge incorporation in the whole range of concentrations (from 0 to unit). Ge alloying promotes grain growth and linearly enlarges the absorber band gap by solely raising the conduction band minimum, which maintains a "spike" conduction band offset at the heterojunction interface until 15% alloying concentration and thus facilitates effective charge carrier collection. A promising efficiency of 11.57% has been achieved at 15% Ge alloying concentration with a significant enhancement in open-circuit voltage and fill factor. By further 10% Ag alloying to improve the absorber film morphology, a champion device with an efficiency of 12.25% has been achieved without an antireflective coating. This result emphasizes the feasibility of achieving homogeneous and controllable Ge alloying of kesterite semiconductors through the solution method, paving the way for further improvement and optimization of device performance.

The status and challenging perspectives of 3D-printed micro-batteries.

In the era of the Internet of Things and wearable electronics, 3D-printed micro-batteries with miniaturization, aesthetic diversity and high aspect ratio, have emerged as a recent innovation that solves the problems of limited design diversity, poor flexibility and low mass loading of materials associated with traditional power sources restricted by the slurry-casting method. Thus, a comprehensive understanding of the rational design of 3D-printed materials, inks, methods, configurations and systems is critical to optimize the electrochemical performance of customizable 3D-printed micro-batteries. In this review, we offer a key overview and systematic discussion on 3D-printed micro-batteries, emphasizing the close relationship between printable materials and printing technology, as well as the reasonable design of inks. Initially, we compare the distinct characteristics of various printing technologies, and subsequently emphatically expound the printable components of micro-batteries and general approaches to prepare printable inks. After that, we focus on the outstanding role played by 3D printing design in the device architecture, battery configuration, performance improvement, and system integration. Finally, the future challenges and perspectives concerning high-performance 3D-printed micro-batteries are adequately highlighted and discussed. This comprehensive discussion aims at providing a blueprint for the design and construction of next-generation 3D-printed micro-batteries.

Surface-engineered Mo2B: a promising electrode material for constructing Ohmic contacts with blue phosphorene for electronic device applications.

The Schottky barrier between a metal and a semiconductor plays an important role in determining the transport efficiency of carriers and improving the performance of devices. In this work, we systematically studied the structure and electronic properties of heterostructures of blue phosphorene (BP) in contact with Mo2B based on density functional theory. The semiconductor properties of BP are destroyed owing to strong interaction with bare Mo2B. The effect of modifying Mo2B with O and OH on the contact properties was investigated. A p-type Schottky contact can be obtained in BP/Mo2BO2. The height of the Schottky barrier can be modulated by interlayer distance to realize a transition from a p-type Schottky contact to a p-type Ohmic contact in BP/Mo2BO2. The BP/Mo2B(OH)2 forms robust Ohmic contacts, which are insensitive to interlayer distance and external electric fields due to the Fermi level pinning effect. Our work provides important clues for contact engineering and improvement of device performance based on BP.

Optimal design of Cs<sub>2</sub>AgBi<sub>0.75</sub>Sb<sub>0.25</sub>Br<sub>6</sub> perovskite solar cells

Double perovskite solar cells have attracted much attention due to their low cost, high performance, environmental friendliness, and strong stability. In this study, the effect of thickness of perovskite layer, band offset, metal electrode work function, the thickness and doping concentration of the transport layer on the efficiency of Cs<sub>2</sub>AgBi<sub>0.75</sub>Sb<sub>0.25</sub>Br<sub>6</sub> solar cells are analyzed by using Silvaco TCAD to improve device performance. This preliminary study of device based on Spiro-OMeTAD as hole transport layer (HTL) and ZnO as electron transport layer (ETL) shows that the photovoltaic conversion efficiency (PCE) is 12.66%. The results show that the efficiency gradually saturates when the thickness of the perovskite layer is greater than 500 nm. The optimal conduction band offset (CBO) ranges from 0 eV to +0.5 eV and the optimal valence band offset (VBO) from –0.1 eV to +0.2 eV. After changing the device's ETL into ZnOS and HTLs into MoO<sub>3</sub>, Cu<sub>2</sub>O and CuSCN, respectively, and optimizing their thickness values and doping concentrations, the final theoretical photovoltaic conversion efficiency of the double perovskite solar cell with an HTL of Cu<sub>2</sub>O can reach 22.85%, which is increased by 25.6% compared with the currently reported theoretical efficiency value. Moreover, the optimal efficiency is achieved when the metal electrode work function is less than –4.9 eV. This work will help find suitable materials for the transport layer and provide guidance for developing the high-performance and lead-free perovskite solar cells.

Optimal design of Cs<sub>2</sub>AgBi<sub>0.75</sub>Sb<sub>0.25</sub>Br<sub>6</sub> perovskite solar cells

Double perovskite solar cells have attracted much attention due to their low cost, high performance, environmental friendliness, and strong stability. In this study, the effect of thickness of perovskite layer, band offset, metal electrode work function, the thickness and doping concentration of the transport layer on the efficiency of Cs<sub>2</sub>AgBi<sub>0.75</sub>Sb<sub>0.25</sub>Br<sub>6</sub> solar cells are analyzed by using Silvaco TCAD to improve device performance. This preliminary study of device based on Spiro-OMeTAD as hole transport layer (HTL) and ZnO as electron transport layer (ETL) shows that the photovoltaic conversion efficiency (PCE) is 12.66%. The results show that the efficiency gradually saturates when the thickness of the perovskite layer is greater than 500 nm. The optimal conduction band offset (CBO) ranges from 0 eV to +0.5 eV and the optimal valence band offset (VBO) from –0.1 eV to +0.2 eV. After changing the device's ETL into ZnOS and HTLs into MoO<sub>3</sub>, Cu<sub>2</sub>O and CuSCN, respectively, and optimizing their thickness values and doping concentrations, the final theoretical photovoltaic conversion efficiency of the double perovskite solar cell with an HTL of Cu<sub>2</sub>O can reach 22.85%, which is increased by 25.6% compared with the currently reported theoretical efficiency value. Moreover, the optimal efficiency is achieved when the metal electrode work function is less than -4.9 eV. This work will help find suitable materials for the transport layer and provide guidance for developing the high-performance and lead-free perovskite solar cells.

Pressure induced mechanical, elastic, and optoelectronic characteristics of Cd0.75Zn0.25Se alloy.

The change in composition and pressure, both of which lead to new desired properties by altering the structure, is particularly important for improving device performance. Given this, we focused here on the mechanical, elastic, and optoelectronic characteristics of the Cd0.75Zn0.25Se alloy using density functional theory at various pressures from 0GPa to 20GPa. It is found that the bulk modulus of the material rises with increasing pressure and exhibits mechanical stability as well as cubic symmetry. In addition, the increased pressure leads to a rise in the direct bandgap energy of the material from 2.03eV to 2.48eV. The absorption coefficient of the alloy also increases as the pressure increases, where the effective range of absorption covers the broad spectrum of light in the visible range from orange to cyan. This is due to the electronic transitions caused by the altered pressure. The optical parameters, including optical conductivity, extinction coefficient, reflection, and refractive index, are also analyzed under the influence of pressure. Based on this research, effective applications of the Cd substituted Zn-chalcogenides (CdZnSe) alloys in the fields of optoelectronics and photovoltaics are outlined, especially concerning fabricating solar cells, photonic devices, and pressure sensors for space technology.

Efficient and stable perovskite solar cells through electrochemically polymerized porphyrin-based hole-transporting materials

The hole-transporting layer (HTL), a pivotal component of perovskite solar cells (PSCs), can significantly improve device performance.

Surface-anchoring fluorinated sulfonate enables efficient and stable perovskite photovoltaics

TFS-TFMS was introduced to modulate the upper interface in n–i–p structured perovskite solar cells, resulting in significantly improved device performance owing to the synergistic engineering of fluorine and sulfonate functional sites.

Effect of substrate temperature and oxygen plasma treatment on the properties of magnetron-sputtered CdS for solar cell applications

Cadmium sulfide (CdS) is an n-type semiconductor with excellent electrical conductivity that is widely used as an electron transport material (ETM) in solar cells. At present, numerous methods for preparing CdS thin films have emerged, among which magnetron sputtering (MS) is one of the most commonly used vacuum techniques. For this type of technique, the substrate temperature is one of the key deposition parameters that affects the interfacial properties between the target film and substrate, determining the specific growth habits of the films. Herein, the effect of substrate temperature on the microstructure and electrical properties of magnetron-sputtered CdS (MS-CdS) films was studied and applied for the first time in hydrothermally deposited antimony selenosulfide (Sb<sub>2</sub>(S,Se)<sub>3</sub>) solar cells. Adjusting the substrate temperature not only results in the design of the flat and dense film with enhanced crystallinity but also leads to the formation of an energy level arrangement with a Sb<sub>2</sub>(S,Se)<sub>3</sub> layer that is more favorable for electron transfer. In addition, we developed an oxygen plasma treatment for CdS, reducing the parasitic absorption of the device and resulting in an increase in the short-circuit current density of the solar cell. This study demonstrates the feasibility of MS-CdS in the fabrication of hydrothermal Sb<sub>2</sub>(S,Se)<sub>3</sub> solar cells and provides interface optimization strategies to improve device performance.

Review—Potential of Tunneling Magnetoresistance Coupled to Iron Oxide Nanoparticles as a Novel Transducer for Biosensors-on-Chip

Biosensors-on-chip (BoC), compact and affordable public diagnostic devices, are vital for preventing health crises caused by viral and bacterial mutations, climate change, and poor diets. Clinical, remote, and field use are possible with these devices. BoC is used in food safety, environmental monitoring, and medical diagnosis. The coupling of tunneling magnetoresistance (TMR) sensing elements in chip form with surface functionalized iron oxide nanoparticles (IONPs) as a biomarker, known as TMR/ IONPs, allows BoC devices to be made. The functional framework of BoC based on TMR/ IONPs, the instrument system, and biomolecule immobilization will be covered in this review. This review aims to overview the recent research on a biosensor using TMR technology with IONPs biomarkers and discuss its future advances in point-of-care diagnostics. TMR sensors have revolutionized low-magnetic field sensing technologies, yet biosensing faces challenges. However, it’s important to recognize that TMR sensors exclusively utilize out-of-plane connections. that creates a larger separation between biomolecules and the sensing layer, leading to a decrease in the sensitivity of biomolecules. Large magnetization of dispersed IONPs to generate sufficient stray-field, compact and inexpensive instrumentation to sense the low voltage yielded by the TMR/IONPs system, and high-selectivity bio-analyte immobilization to the surface of IONPs to increase sensor sensitivity are the notable issues to address this problem. The utilization of the green synthesized method in producing IONPs for magnetic labeling can enhance the sensitivity of a TMR-based biosensor. This is achieved through the formation of IONPs with a capping agent on its surface that inhibits the aggregation and facilitates the immobilization of the biomolecule target. Additionally, improving device performance requires creating high-TMR materials. Despite challenges, research and technological advances hold great promise for TMR/GS-IONP bio-applications.

Efficiency enhancement and doping type inversion in Cu2CdSnS4 solar cells by Ag substitution

Silver substitution on Cu2CdSnS4 solar cells improves device performance at small doping concentrations. Structural and properties changes are induced with higher silver alloying amounts.

Inhibition of ion diffusion/migration in perovskite p-n homojunction by polyetheramine insert layer to enhance stability of perovskite solar cells with p-n homojunction structure.

Perovskite p-n homojunctions (PHJ) have been confirmed to play a crucial role in facilitating carrier separation/extraction in the perovskite absorption layer and provide an additional built-in potential, which benefits the inhibition of carrier recombination in perovskite solar cells (PSCs) and ultimately improves device performance. However, the diffusion and migration of ions between n-type and p-type perovskite films, particularly under operational and heating conditions, lead to the degradation of PHJ structures and limit the long-term stability of PSCs with PHJ structure (denoted as PHJ-PSCs). In this study, we propose an insert layer strategy by directly introducing an ultra-thin polyetheramine (PEA) layer between the n-type and p-type perovskite films to address those challenges arising from ion movements. Femtosecond transient absorption (fs-TAS) and photoluminescence (PL) measurements demonstrate that the PHJ (without and with the insert layer) enhances carrier separation/extraction compared to the single n-type perovskite film. Monitoring the evolution of bromine element distribution reveals that the insert layer can efficiently suppress ion diffusion between perovskite films, even under long-term illumination and heating conditions. Consequently, an efficiency of 23.53% with excellent long-term operational stability is achieved in the optimized PHJ-PSC with the insert layer.