ABSTRACT
Ultraviolet C (UVC) photodetectors have garnered considerable attention recently because the detection of UVC is critical for preventing skin damage in humans, monitoring environmental conditions, detecting power aging in facilities, and military applications. As UVC detectors are "solar-blind", they encounter less interference than other environmental signals, resulting in low disturbance levels. This study employed a natural precursor (glucose) and a one-step ultrasonic reaction procedure to prepare carbon quantum dots (CQDs), which served as a convenient and environmentally friendly material to combine with polyethyleneimine (PEI). The prepared materials were used to develop a self-powered, high-performance UVC photodetector. The thickness of the constitutive film was investigated in detail based on the conditions of the electron transport pathway and trap positions to further improve the performance of the PEI/CQD photodetectors. Under the optimized conditions, the photodetector could generate a strong signal (1.5 mA W-1 at 254 nm) and exhibit high detectability (1.8 × 1010 Jones at 254 nm), an ultrafast response, and long-term stability during the power supply sequence. The developed solar-blind UVC photodetector can be applied in various ways to monitor UVC in an affordable, straightforward, and precise manner.
ABSTRACT
To produce highly efficient and repeatable perovskite solar cells (PSCs), comprehending interfacial loss and developing approaches to ameliorate interfacial features is essential. Nonradiative recombination at the SnO2-perovskite interface in SnO2-based perovskite solar cells (PSCs) leads to significant potential loss and variability in device performance. To improve the quality of the SnO2 electron transport layer, a novel polymer-doped SnO2 matrix, specifically using polyacrylic acid, was developed. This matrix is formed by spin-coating a SnO2 colloidal solution that includes polymers. The polymer aids in dispersing nanoparticles within the substrate and is evenly distributed in the SnO2 solution. As a result of the polymer addition, the density and wetting properties of the SnO2 layer substantially improved. Subsequently, perovskite-based photovoltaic devices comprising SnO2 and Spiro-OMeTAD layers and using (FAPbI3)0.97(MAPbBr3)0.03 perovskite are constructed. These optimized devices exhibited an increased efficiency of 17.2% when compared to the 15.7% power conversion efficiency of the control device. The incorporation of polymers in the electron transport layer potentially enables even better performance in planar perovskite solar cells.
ABSTRACT
In this study, a highly crystalline and transparent indium-tin-oxide (ITO) thin film was prepared on a quartz substrate via RF sputtering to fabricate an efficient bottom-to-top illuminated electrode for an ultraviolet C (UVC) photodetector. Accordingly, the 26.6 nm thick ITO thin film, which was deposited using the sputtering method followed by post-annealing treatment, exhibited good transparency to deep-UV spectra (67% at a wavelength of 254 nm), along with high electrical conductivity (11.3 S/cm). Under 254 nm UVC illumination, the lead-halide-perovskite-based photodetector developed on the prepared ITO electrode in a vertical structure exhibited an excellent on/off ratio of 1.05 × 104, a superb responsivity of 250.98 mA/W, and a high specific detectivity of 4.71 × 1012 Jones without external energy consumption. This study indicates that post-annealed ITO ultrathin films can be used as electrodes that satisfy both the electrical conductivity and deep-UV transparency requirements for high-performance bottom-illuminated optoelectronic devices, particularly for use in UVC photodetectors.
ABSTRACT
Al-doped ZnO (AZO) thin films are effective n-type semiconductors for ultraviolet (UV) detection because of their low cost, high electron mobility, and high sensitivity to UV light, especially in the UVA spectrum. However, a reasonable compromise between performance (such as sensitivity, detectivity, and response time) and fabrication ease remains an obstacle to the practicability of AZO-based UV photodetectors. To address this issue, we propose an efficient strategy to achieve a large AZO photoactive area for outstanding performance, along with a facile sol-gel method. Consequently, the device exhibits a superb on/off ratio of >104, a high detectivity of 1.85 × 1012 Jones, and a fast response speed under 365 nm UVA illumination without external energy consumption. Hence, this study suggests a self-powered and high-performance nanoporous AZO-based UVA detector with an environmentally friendly scalable process that satisfies industrial production requirements for numerous practical UV-detection applications.
ABSTRACT
Perovskite solar cells (PSCs) have garnered considerable attention over the past decade owing to their low cost and proven high power conversion efficiency of over 25%. In the planar heterojunction PSC structure, tin oxide was utilized as a substitute material for the TiO2 electron transport layer (ETL) owing to its similar physical properties and high mobility, which is suitable for electron mining. Nevertheless, the defects and morphology significantly changed the performance of SnO2 according to the different deposition techniques, resulting in the poor performance of PSCs. In this review, we provide a comprehensive insight into the factors that specifically influence the ETL in PSC. The properties of the SnO2 materials are briefly introduced. In particular, the general operating principles, as well as the suitability level of doping in SnO2, are elucidated along with the details of the obtained results. Subsequently, the potential for doping is evaluated from the obtained results to achieve better results in PSCs. This review aims to provide a systematic and comprehensive understanding of the effects of different types of doping on the performance of ETL SnO2 and potentially instigate further development of PSCs with an extension to SnO2-based PSCs.
ABSTRACT
Ultraviolet-C (UVC) photodetector has appealed to a numerous number of research owing to its manifold applications in wireless communication, flame monitoring, and medicine. However, in addition to superior performance and high stability of recent studies, scalability and production cost are important factors for commercialization and practical implementation. In this study, a halide perovskite-based UVC photodetector was fabricated using spin-coating process and low-temperature annealing. Corning® Willow® Glass was selected as the substrate for the bottom-illuminated device due to its flexibility and exceptional optical transmission (approximately 60%) in the deep-UV region. The device had a vertical structure with a large active area (1 cm2) owing to the judicious utilization of electrodes. Under bent state with a curvature radius of 25 mm, the as-fabricated device exhibited high response and repeatability with an on/off ratio of 9.57 × 103, a fast response speed of 45/46 ms (rise/fall times) at zero bias under the illumination of a 254-nm UV lamp. The results are based on a flexible and lightweight photodetector without the utilization of notable metal electrodes.
ABSTRACT
The effective use of a europium metal-organic framework (Eu-MOF) as a photoabsorber material has been reported. Using the advantages of Eu-MOFs including simple preparation, wide bandgap structure, and stability in the environment, a self-powered and high UVC-selectivity detector based on Eu-MOF nanoparticles was prepared with a simple device geometry. The as-fabricated photodetector was highly sensitive to 254 nm UV illumination without an external power supply. Accordingly, it exhibited a high UVC-to-UVA rejection ratio (I254/I365 ≈ 40) and UVC-to-solar rejection ratio (I254/Isolar light ≈ 34), a fast response time of 98/122 ms, a comparable on/off photocurrent ratio (107.33), and superior stability. The self-powered Eu-MOF photodetector can detect and monitor UV emission from an invisible fire in an early state at room temperature, suggesting practical use as a potential optoelectronic device.
ABSTRACT
Controlling phase transitions in correlated materials yields emergent functional properties, providing new aspects to future electronics and a fundamental understanding of condensed matter systems. With vanadium dioxide (VO2 ), a representative correlated material, an approach to control a metal-insulator transition (MIT) behavior is developed by employing a heteroepitaxial structure with a ferroelectric BiFeO3 (BFO) layer to modulate the interaction of correlated electrons. Owing to the defect-alleviated interfaces, the enhanced coupling between the correlated electrons and ferroelectric polarization is successfully demonstrated by showing a nonvolatile control of MIT of VO2 at room temperature. The ferroelectrically-tunable MIT can be realized through the Mott transistor (VO2 /BFO/SrRuO3 ) with a remanent polarization of 80 µC cm-2 , leading to a nonvolatile MIT behavior through the reversible electrical conductance with a large on/off ratio (≈102 ), long retention time (≈104 s), and high endurance (≈103 cycles). Furthermore, the structural phase transition of VO2 is corroborated by ferroelectric polarization through in situ Raman mapping analysis. This study provides novel design principles for heteroepitaxial correlated materials and innovative insight to modulate multifunctional properties.
ABSTRACT
Ultraviolet-C (UVC) radiation is employed in various applications, including irreplaceable applications in military and civil fields, such as missile guidance, flame detection, partial discharge detection, disinfection, and wireless communication. Although most modern electronics are based on Si, UVC detection technology remains a unique exception because the short wavelength of UV radiation makes efficient detection with Si difficult. In this review, recent challenges in obtaining ideal UVC photodetectors with various materials and various forms are introduced. An ideal photodetector must satisfy the following requirements: high sensitivity, fast response speed, high on/off photocurrent ratio, good regional selectivity, outstanding reproducibility, and superior thermal and photo stabilities. UVC detection is still in its infancy compared to the detection of UVA as well as other photon spectra, and recent research has focused on different key components, including the configuration, material, and substrate, to acquire battery-free, super-sensitive, ultra-stable, ultra-small, and portable UVC photodetectors. We introduce and discuss the strategies for fabricating self-powered UVC photodetectors on flexible substrates in terms of the structure, material, and direction of incoming radiation. We also explain the physical mechanisms of self-powered devices with various architectures. Finally, we present a brief outlook that discusses the challenges and future strategies for deep-UVC photodetectors.
ABSTRACT
Flexible and self-powered photodetectors (PDs) have become one of the most popular topics, attracting researchers in the field of optoelectronic applications. In this study, for the first time, we demonstrate partial discharge detection in a practical environment with a prepared flexible device. Poly(vinylidene fluoride) (PVDF) is utilized as a highly transparent material in the UVC region, to create a flexible substrate with the antihumidity property. A detector that uses a mixed-halide perovskite (FAPbI3)1-x(MAPbBr3)x as the photoactive material is constructed in a vertical structure on the as-prepared hydrophobic PVDF substrate. The fabricated device exhibits good performance with a fast response speed (trise = 82 ms, tfall = 64 ms) and a high detectivity of 7.21 × 1010 Jones at zero bias under 254 nm UV illumination, along with superior mechanical flexibility at various bending angles. Additionally, the air-exposure stability and reproducibility of the as-prepared device exhibit almost the original performance after 6 weeks of storage. For practical applications, we demonstrate a facile and sensitive detection for UVC leakage from a germicidal lamp and simulated a partial discharge system using our PD without energy consumption. These results indicate that this new approach may be useful and convenient for the detection of the partial discharge as well as for several practical applications.
ABSTRACT
Over the past few decades, silicon-based solar cells have been used in the photovoltaic (PV) industry because of the abundance of silicon material and the mature fabrication process. However, as more electrical devices with wearable and portable functions are required, silicon-based PV solar cells have been developed to create solar cells that are flexible, lightweight, and thin. Unlike flexible PV systems (inorganic and organic), the drawbacks of silicon-based solar cells are that they are difficult to fabricate as flexible solar cells. However, new technologies have emerged for flexible solar cells with silicon. In this paper, we describe the basic energy-conversion mechanism from light and introduce various silicon-based manufacturing technologies for flexible solar cells. In addition, for high energy-conversion efficiency, we deal with various technologies (process, structure, and materials).
ABSTRACT
Understanding metal-to-insulator phase transitions in solids has been a keystone not only for discovering novel physical phenomena in condensed matter physics but also for achieving scientific breakthroughs in materials science. In this work, we demonstrate that the transport properties (i.e., resistivity and transition temperature) in the metal-to-insulator transitions of perovskite nickelates are tunable via the epitaxial heterojunctions of LaNiO3 and NdNiO3 thin films. A mismatch in the oxygen coordination environment and interfacial octahedral coupling at the oxide heterointerface allows us to realize an exotic phase that is unattainable in the parent compound. With oxygen vacancy formation for strain accommodation, the topmost LaNiO3 layer in LaNiO3/NdNiO3 bilayer thin films is structurally engineered and it electrically undergoes a metal-to-insulator transition that does not appear in metallic LaNiO3. Modification of the NdNiO3 template layer thickness provides an additional knob for tailoring the tilting angles of corner-connected NiO6 octahedra and the linked transport characteristics further. Our approaches can be harnessed to tune physical properties in complex oxides and to realize exotic physical phenomena through oxide thin-film heterostructuring.
ABSTRACT
Piezoelectric nanogenerators (PNGs) have been studied as renewable energy sources. PNGs consisting of organic piezoelectric materials such as poly(vinylidene fluoride) (PVDF) containing oxide complex powder have attracted much attention for their stretchable and high-performance energy conversion. In this study, we prepared a PNG combined with PVDF and lanthanum-modified bismuth titanate (Bi4-XLaXTi3O12, BLT) ceramics as representative ferroelectric materials. The inserted BLT powder was treated by high-speed ball milling and its particle size reduced to the nanoscale. We also investigated the effect of particle size on the energy-harvesting performance of PNG without polling. As a result, nano-sized powder has a much larger surface area than micro-sized powder and is uniformly distributed inside the PNG. Moreover, nano-sized powder-mixed PNG generated higher power energy (> 4 times) than the PNG inserted micro-sized powder.
ABSTRACT
The use of composites such as hydroxyapatite (HA)/TiO2in bioapplications has attracted increasing attention in recent years. Herein, for the enhancement wetting ability and biocompatibility, the HA/TiO2composite was subjected to different treatments to improve nanoparticle (NP) distribution and surface energy with an aim of mitigating nanotoxicity concerns. The treatments included ultrasonication, high-temperature annealing, and addition of a dispersant and surfactant, sodium dodecylbenzenesulfonate (SDBS). Contact angle measurement tests revealed the effect of SDBS addition on the distribution of TiO2NPs on the HA surface: a decrease in the contact angle and, thus, an increase in the wetting ability of the HA/TiO2composite were observed. The combination of annealing and SDBS addition treatments allowed for guest TiO2particles to be uniformly distributed on the surface of the host HA particles, showing a rapid conversion from a hydrophobic to superhydrophilic property.In vitroinvestigation suggested that the cell viabilities of annealed HA/TiO2, SDBS-added HA/TiO2, and SDBS-added and annealed HA/TiO2reached 89.7%, 94.7%, and 95.8%, respectively, while those of HA and untreated HA/TiO2were 80.3% and 86.9%, respectively. The modified composites exhibited lower cytotoxicities than the unmodified systems (HA and HA/TiO2). Furthermore, the cell adhesion behavior of the composites was confirmed through actin-4',6-Diamidino-2-phenylindole (DAPI) staining, which showed negligible changes in the cytoskeleton architecture of the cells. This study confirmed that a modified HA/TiO2composite has potential for bioapplications.
Subject(s)
Benzenesulfonates/chemistry , Durapatite , Nanostructures/chemistry , Surface-Active Agents/chemistry , Titanium , Cell Survival , Drug Stability , Durapatite/chemistry , Durapatite/pharmacokinetics , Durapatite/pharmacology , HeLa Cells , Hot Temperature , Humans , Materials Testing , Sonication , Titanium/chemistry , Titanium/pharmacokinetics , Titanium/pharmacology , WettabilityABSTRACT
In this study, a simply structured perovskite-based ultraviolet C (UVC) sensor was prepared using a one-step, low-temperature solution-processing coating method. The UVC sensor utilized CH3NH3PbBr3 perovskite as the light-absorbing layer. To improve the characteristics of CH3NH3PbBr3, an antisolvent process using toluene and the addition of CH3NH3Cl were introduced. The device with these modifications exhibited a response rise/fall time of 15.8/16.2 ms, mobility of 158.7 cm2/V·s, responsivity of 4.57 mA/W, detectivity of 1.02 × 1013 Jones, and external quantum efficiency of 22.32% under the 254-nm UV illumination. Therefore, this methodology could be a good approach in facilitating UVC detection.
ABSTRACT
The perovskite solar cell is capable of energy conversion in a wide range of wavelengths, from 300 nm to 800 nm, which includes the entire visible region and portions of the ultraviolet and infrared regions. To increase light transmittance of perovskite solar cells and reduce manufacturing cost of perovskite solar cells, soda-lime glass and transparent conducting oxides, such as indium tin oxide and fluorine-doped tin oxide are mainly used as substrates and light-transmitting electrodes, respectively. However, it is evident from the transmittance of soda-lime glass and transparent conductive oxides measured via UV-Vis spectrometry that they absorb all light near and below 310 nm. In this study, a transparent Mn-doped ZnGa2O4 film was fabricated on the incident surface of perovskite solar cells to obtain additional light energy by down-converting 300 nm UV light to 510 nm visible light. We confirmed the improvement of power efficiency by applying a ZnGa2O4:Mn down-conversion layer to perovskite solar cells.
ABSTRACT
Organic material-based solar cell devices such as perovskite solar cells (PSCs) have attracted attention as renewable energy resources with low production cost, lightweight, wearable device applications, and large-area processability. To enhance device performance, many research groups have attempted to develop new materials and structures. Metal electrode materials play an important role in solar energy conversion in PSCs, owing to the ohmic contact and contact resistance between metal negative electrodes and photoactive layers. Until recently, conventional metal sources such as Ag, Au, or Cu have been used as electrodes. In this study, PSCs were employed in various metal negative electrodes using a thermal evaporator. The authors investigated the effect of metal negative electrodes on PSCs.
ABSTRACT
Perovskite solar cells have been attracting extensive attention because of their superior photovoltaic performances and lower costs as compared to those of prevailing photovoltaic technologies. There are four main interfaces in perovskite solar cells: flourine-doped tin oxide/electron transport layer, electron transport layer/perovskite layer, perovskite layer/hole transport layer, and hole transport layer/metal electrode. Among them, the interface between the perovskite layer (general formula RPbX3) and electron transport layer significantly affects the power conversion efficiency. In this study, a layer of TiO2, which is the most popular metal oxides used for perovskite solar cells applications, was deposited as the electron transport layer. To enhance the perovskite solar cells performance, surface treatment was performed with TiCl4 (80 mM). To investigate the effect of TiCl4 treatment, ultraviolet-visible spectroscopy was performed on the perovskite film. Atomic force microscopy, X-ray diffraction, scanning electron microscopy and performance of perovskite solar cells have been also evaluated in this paper. The results indicated that the TiCl4 treatment significantly improved the perovskite solar cells performance.
ABSTRACT
In recent years, the optical behavior of complex oxides are being increasingly used in light-harvesting applications. Perovskites are promising candidates for photovoltaic, photocatalytic, and optoelectric applications because of tunable band gaps and other unique properties such as fer-roelectricity To study the optical behavior of ferromagnetic-ferroelectric oxides, SrMnO3 (SMO3) targets intended for use in magnetron sputtering were prepared using SrCO3 (99.99%) and Mn2O3 (99.99%) powders by a two-step solid reaction method. Experiments were performed at various temperatures to determine the optimum calcination temperature of the SMO3 powder (1000 °C) and optimum sintering temperature of the prepared target (1300 °C), in an effort to optimize the preparation process of the target at the laboratory scale and reduce the cost of the target by more than 20-fold. Samples of the ground powder were calcined at 800, 1000, 1200, and 1300 °C for 10 h, and the resultant targets were pressed into 1 -in molds after grinding and subsequently sintered at the same temperatures at which the corresponding powders were calcined, i.e., at 800, 1000, 1200, and 1300 °Cfor 48 h. The microcrystalline state of the powders was observed by scanning electron microscopy. The prepared targets were analyzed by X-ray diffraction, and the results were compared with the powder diffraction file card of hexagonal SMO3 to determine the optimum calcination temperature and sintering temperature of the powder formulation. Finally, the Vickers hardness values of the targets were measured, and the optimum target preparation process was determined.
ABSTRACT
The electron transport layer (ETL) of organic-inorganic perovskite solar cells plays an important role in their power conversion efficiency (PCE). In this study, TiO2 hollow nanospheres with a diameter of 150 nm were prepared by a facile synthesis method. The synthesized TiO2 hollow nanospheres had a highly porous structure with a surface area of 85.23 m2 g-1, which is significantly higher than commercial TiO2 (P25) (54.32 m2 g-1), indicating that they can form an ideal mesoporous layer for Formamidinium iodide-based perovskite solar cells (PSCs). In addition, the nanospheres achieved a remarkable perovskite performance, and the average PCE increased from 12.87% to 14.27% with a short circuit current density of 22.36 mAcm-2, an open voltage of 0.95 V, and a fill factor of 0.65. The scanning electron microscopy images revealed that the enhanced PCE could be due to the improved carrier collection and transport properties of the nanosphere, which enabled efficient filtration of perovskite into the TiO2 mesoporous ETL. The TiO2 hollow nanospheres fabricated in this study show high potential as a high-quality ETL material for efficient (FAPbI3)0.97(MAPbBr3)0.03-based PSCs.
