Tandem Structure Research Articles

Optical simulation and experimental investigation of the crystalline silicon/black silicon/perovskite tandem structures

The use of a black silicon (b-Si) interlayer is a promising solution for improving the optical properties of crystalline Si/perovskite solar cells. Optical numerical simulation of the crystalline Si/b-Si/perovskite structures can efficiently optimize their parameters at the initial tandem solar cell design stage. In this work, the optical properties of these structures were modeled using the transfer matrix method, where an array of cone-like nanoneedles of the b-Si interlayer is approximated as a homogeneous optical medium, for which the effective complex refractive index is the weighted average of those for Si and perovskite. Analytical equations are obtained for tandem structures' reflection, transmission, and absorption. The simulated reflectance spectra of the structures were compared with those of structures without the b-Si layer, as well as with experimental data. Numerical calculations and experiments confirm that nanotexturing significantly improves the optical properties of tandem structures. In addition, the nanotextured tandem structures have a wide-angle antireflective characteristic at incidence angles less than 60°, indicating their omnidirectional light-trapping capability. The proposed simulation model satisfactorily describes the optical behavior of crystalline Si/b-Si/perovskite tandem structures and can be used to estimate their optical properties depending on various parameters. As a demonstration, a numerical analysis was performed to study the effect of the b-Si interlayer thickness on the reflection of the tandem structure.

A UV-Reflective Organic-Inorganic Tandem Structure for Efficient and Durable Daytime Radiative Cooling in Harsh Climates.

Radiative cooling shows great promise in eco-friendly space cooling due to its zero-energy consumption. For subambient cooling in hot humid subtropical/tropical climates, achieving ultrahigh solar reflectance (≥96%), durable ultraviolet (UV) resistance, and surface superhydrophobicity simultaneously is critical, which, however, is challenging for most state-of-the-art scalable polymer-based coolers. Here an organic-inorganic tandem structure is reported to address this challenge, which comprises a bottom high-refractive-index polyethersulfone (PES) cooling layer with bimodal honeycomb pores, an alumina (Al2 O3 ) nanoparticle UV reflecting layer with superhydrophobicity, and a middle UV absorption layer of titanium dioxide (TiO2 ) nanoparticles, thus providing thorough protection from UV and self-cleaning capability together with outstanding cooling performance. The PES-TiO2 -Al2 O3 cooler demonstrates a record-high solar reflectance of over 0.97 and high mid-infrared emissivity of 0.92, which can maintain their optical properties intact even after equivalent 280-day UV exposure despite the UV-sensitivity of PES. This cooler achieves a subambient cooling temperature up to 3 °C at summer noontime and 5 °C at autumn noontime without solar shading or convection cover in a subtropical coastal city, Hong Kong. This tandem structure can be extended to other polymer-based designs, offering a UV-resist but reliable radiative cooling solution in hot humid climates.

Variation of Charge Carrier Dynamics for Polycrystalline Perovskite Films by One-Step Solution and Vapor-Deposition Methods.

To date, solution-processing and vapor-deposition fabrication methods have achieved huge successes in high-efficiency perovskite solar cells (PSCs) and satisfy special demanding requirements for diverse application purposes, respectively. Although people realize that the fabrication procedure is crucial in device performance, insightful studies of charge carrier dynamics in perovskite films by different methods still lack. In this work, we compare the carrier behaviors in one-step spin-coated and dual-source coevaporated MAPbI3 perovskite films by combining time-resolved photoluminescence spectroscopy and carrier dynamics simulation. We suggest that strains, lattice orientations, and defects at buried side of perovskite films, which are associated with different preparation processes, lead to variations in carrier behaviors. Hence fabrication of perovskite layers should be elaborately designed in order to satisfy the needs of different carrier behaviors in specified device configurations of PSCs such as smooth planar or textured monolithic tandem structures.

Electrical and thermomechanical evaluation of the bifacial PV-STEG and tandem PV-STEG units under uniform and nonuniform radiation conditions

The structural failure threats the long-term stable operation of the photovoltaic-solar thermoelectric generator (PV-STEG) system. In this study, a comprehensive numerical model is developed to analyze the electrical and thermomechanical performance of the conventional tandem photovoltaic-solar thermoelectric generator (TA-PV-STEG) layout and bifacial structure of photovoltaic-solar thermoelectric generator (BI-PV-STEG) layout under uniform and nonuniform radiation conditions. The effects of sun concentration ratio (CR), inlet temperature, and leg height on the performance of the systems are examined in detail. In addition, the consequences of utilizing solar cells with varying temperature coefficients (cell1: 0.004 1/K and cell2: 0.001 1/K) and standard efficiencies (cell1: 15% and cell2: 10%) are also accounted for. The results demonstrate that the bifacial structure could provide better overall performance than the tandem structure. The maximum cell temperature difference under uniform radiation is greater than 19 K, and the corresponding percentage increase in cell power output is 9.28%. The increase in CR and leg height leads to higher STEG output, while the lower inlet temperature is preferable. Moreover, although cell2 possesses a lower temperature coefficient, the electrical performance of cell1 is higher than cell2 in most conditions. The maximum thermal stress observed in the bifacial structure is greater than that of the tandem structure due to the wider temperature gradient. Therefore, this study provides direction for designing the actual PV-STEG system in consideration of thermal stress distribution side effects.

TCAD Device Simulation of All-Polymer Solar Cells for Indoor Applications: Potential for Tandem vs. Single Junction Cells.

The utilization of indoor photovoltaics makes it feasible to harvest energy from artificial light sources. Although single-junction indoor photovoltaics have demonstrated exceptional efficacy when using LED lighting, there is still a need for more comprehensive testing of tandem structures. Herein, the first systematic TCAD simulation study on the potential for tandem all-polymer solar cells (all-PSCs) for indoor applications is provided. The presented all-PSCs are based on experimental work in which the top wide bandgap subcell comprises a polymer blend PM7:PIDT, while the bottom narrow bandgap subcell has a polymer blend PM6:PY-IT. Standalone and tandem cells are simulated under AM1.5G solar radiation, and the simulation results are compared with measurements to calibrate the physical models and material parameters revealing PCE values of 10.11%, 16.50%, and 17.58% for the front, rear, and tandem cells, respectively. Next, we assessed the performance characteristics of the three cells under a white LED environment for different color temperatures and light intensities. The results showed a superior performance of the front cell, while a deterioration in the performance was observed for the tandem cell, reflecting in a lower PCE of 16.22% at a color temperature of 2900 K. Thus, an optimized tandem for outdoor applications was not suitable for indoor conditions. In order to alleviate this issue, we propose designing the tandem for indoor lightening by an appropriate choice of thicknesses of the top and bottom absorber layers in order to achieve the current matching point. Reducing the top absorber thickness while slightly increasing the bottom thickness resulted in a higher PCE of 27.80% at 2900 K.

Blue-Hazard-Free Organic Light-Emitting Diode with a Lifetime Greater than 200,000 h

Blue-hazard-free lighting is in urgent need in order to protect human eyes and physiology. A candlelight-style organic light emitting diode (OLED) is so far the safest measure for its blue-hazard-free, low-color-temperature illumination. However, lifetime is still the most critical reliability issue in OLEDs, especially in lighting applications that are closely associated with high current density operation. Here, we present a novel approach to develop blue-hazard-free OLEDs with a lifetime exceeding 200,000 h at 1000 cd/m2 by employing a tandem structure with ultra-high purity emitter. The resultant device shows a current efficacy of 37.4 cd/A, an external quantum efficiency (EQE) of 22.7%, an 80 CRI, and a 78 SRI with a 223,500 h lifetime (t50). Additionally, the resultant device also exhibits a long retina exposure duration of 12,300 s (3.42 h) and suppresses very less melatonin generation (1.7%), demonstrating that the fabricated OLED device is a highly prospective general lighting source to safeguard human health.

Optical Simulation-Aided Design and Engineering of Monolithic Perovskite/Silicon Tandem Solar Cells.

Monolithic perovskite/c-Si tandem solar cells have attracted enormous research attention and have achieved efficiencies above 30%. This work describes the development of monolithic tandem solar cells based on silicon heterojunction (SHJ) bottom- and perovskite top-cells and highlights light management techniques assisted by optical simulation. We first engineered (i)a-Si:H passivating layers for (100)-oriented flat c-Si surfaces and combined them with various (n)a-Si:H, (n)nc-Si:H, and (n)nc-SiOx:H interfacial layers for SHJ bottom-cells. In a symmetrical configuration, a long minority carrier lifetime of 16.9 ms was achieved when combining (i)a-Si:H bilayers with (n)nc-Si:H (extracted at the minority carrier density of 1015 cm-3). The perovskite sub-cell uses a photostable mixed-halide composition and surface passivation strategies to minimize energetic losses at charge-transport interfaces. This allows tandem efficiencies above 23% (a maximum of 24.6%) to be achieved using all three types of (n)-layers. Observations from experimentally prepared devices and optical simulations indicate that both (n)nc-SiOx:H and (n)nc-Si:H are promising for use in high-efficiency tandem solar cells. This is possible due to minimized reflection at the interfaces between the perovskite and SHJ sub-cells by optimized interference effects, demonstrating the applicability of such light management techniques to various tandem structures.

Optically Transparent and Mechanically Robust Ionic Hydrogel Electrodes for Bright Electroluminescent Devices Achieving High Stretchability Over 1400%

AbstractTo realize wearable displays and interactive soft robots, significant research efforts are focused on developing highly deformable alternating‐current electroluminescent (ACEL) devices. Although soft emission layers are well developed, designing stretchable, conductive, and transparent soft electrodes remains challenging. In this study, ionic hydrogels are prepared comprising a double network (DN) of poly(N‐hydroxyethylacrylamide‐co‐acrylamide)/crosslinked chitosan swollen in aqueous lithium bis(trifluoromethanesulfonyl) imide. Owing to the finely tuned DN structure of the polymeric crosslinker and transparent electrolyte, the developed ionic hydrogels exhibit remarkable stretchability (1400%), excellent optical transmittance (>99%), and high conductivity (1.95 × 10−2 Sm−1). Based on the high performance of the ionic hydrogels, ACEL devices are fabricated with an emission layer containing phosphor microparticles and demonstrate stable, high luminance under extreme deformation, and ultra‐high elongation. The excellent transparency of the ionic hydrogel further enables the fabrication of novel soft ACEL devices with tandem structures by stacking several emission and electrode layers, in which each emission layer is independently controlled with a switch circuit.

Pilot‐scale demonstration of novel tandem coating process: Combining dispersion and extrusion coating with enhanced barrier properties

AbstractIncreasing environmental and legislative demands have accelerated the development of new packaging materials and processes toward more sustainable alternatives. Furthermore, barrier properties of the packaging have become increasingly important, as food waste creates environmental problems. Nowadays, multilayer structures are typically used to create required barrier properties to the packages. The aim of the study was to combine dispersion and extrusion coating into consecutive tandem process to produce two‐layer structure with enhanced barrier properties. By combining two processing steps into one, time and resources are saved. The study presents demonstration of the tandem coating in pilot‐scale. The process was tested with several different materials and combinations and the processing conditions were optimized to produce optimal layer structure and properties. The properties of samples were analyzed with microscopy imaging, pinhole measurement and barrier measurements including oxygen, water vapor and grease permeation. Single layer of dispersion coatings could not produce continuous film, but the extrusion coatings filled the pinholes and enabled low permeation values. The permeabilities of the tandem coated structures were promising and generally lower than the sum of two individual layers. Moreover, the tandem coated structures produced with sustainable alternatives, performed better than traditional materials in oxygen and grease permeation measurements.

Dye‐Sensitized Solar Cells with Efficiency over 36% under Ambient Light Achieved by Cosensitized Tandem Structure

The cosensitization process is an effective way to improve the performance of dye‐sensitized solar cells (DSSCs), especially for tandem cells that employ the complementary light harvest ranges of different dyes. Herein, various cosensitized DSSCs are prepared using D35, XY1b, and Y123 dyes and employed to construct cobalt tandem DSSCs. First, the performance of single cells with and without scattering layers is studied. The results show that the cosensitized cells using D35 + XY1b and XY1b + Y123 dyes have higher power conversion efficiency (PCE) than the others, attributed to their longer light absorption wavelength and higher charge recombination resistance. Furthermore, the XY1b + Y123 cell has significantly higher open circuit voltage (Voc) but slightly lower current density (Jsc) than those of the D35 + XY1b cell. The cosensitized systems are further utilized to prepare tandem cells. Photoelectrodes without and with scattering layers are used as top and bottom cells, respectively. It shows that by using D35 + XY1b (higher Jsc) and XY1b + Y123 (higher Voc) as sensitizers of top and bottom cells, respectively, a PCE as high as 36.27% can be achieved under fluorescent lighting. The cells using these dyes have high long‐term stability at room temperature.

Utilizing machine learning algorithm in predicting the power conversion efficiency limit of a monolithically perovskites/silicon tandem structure

Tandem structures have been introduced to the photovoltaics (PV) market to boost power conversion efficiency (PCE). Single-junction cells’ PCE, either in a homojunction or heterojunction format, are clipped to a theoretical limit associated with the absorbing material bandgap. Scaling up the single-junction cells to a multi-junction tandem structure penetrates such limits. One of the promising tandem structures is the perovskite over silicon topology. Si junction is utilized as a counter bare cell with perovskites layer above, under applying the bandgap engineering aspects. Herein, we adopt BaTiO 3 /CsPbCl 3 /MAPbBr 3 /CH 3 NH 3 PbI 3 /c-Si tandem structure to be investigated. In tandem PVs, various input parameters can be tuned to maximize PCE, leading to a massive increase in the input combinations. Such a vast dataset directly reflects the computational requirements needed to simulate the wide range of combinations and the computational time. In this study, we seed our random-forest machine learning model with the 3×10 6 points’ dataset with our optoelectronic numerical model in SCAPS. The machine learning could estimate the maximum PCE limit of the proposed tandem structure at around 37.8%, which is more than double the bare Si-cell reported by 18%.

Comparative genomics analysis of endangered wild Egyptian Moringa peregrina (Forssk.) Fiori plastome, with implications for the evolution of Brassicales order.

Moringa is a mono-genus belonging to the Moringaceae family, which includes 13 species. Among them, Moringa peregrina is plant species native to the Arabian Peninsula, Southern Sinai in Egypt, and the Horn of Africa, and comprehensive studies on its nutritional, industrial, and medicinal values have been performed. Herein, we sequenced and analyzed the initial complete chloroplast genome of Moringa peregrina. Concurrently, we analyzed the new chloroplast genome along with 25 chloroplast genomes related to species representing eight families in the Brassicales order. The results indicate that the plastome sequence of M. peregrina consists of 131 genes, with an average GC content of 39.23%. There is a disparity in the IR regions of the 26 species ranging from 25,804 to 31,477 bp. Plastome structural variations generated 20 hotspot regions that could be considered prospective DNA barcode locations in the Brassicales order. Tandem repeats and SSR structures are reported as significant evidence of structural variations among the 26 tested specimens. Furthermore, selective pressure analysis was performed to estimate the substitution rate within the Moringaceae family, which revealing that the ndhA and accD genes are under positive selective pressure. The phylogenetic analysis of the Brassicales order produced an accurate monophyletic annotation cluster of the Moringaceae and Capparaceae species, offering unambiguous identification without overlapping groups between M. oleifera and M. peregrina, which are genetically strongly associated. Divergence time estimation suggests that the two Moringa species recently diversified, 0.467Ma. Our findings highlight the first complete plastome of the Egyptian wild-type of M. peregrina, which can be used for determining plastome phylogenetic relationships and systematic evolution history within studies on the Moringaceae family.

Image-based scatter correction for cone-beam CT using flip swin transformer U-shape network.

Cone beam computed tomography (CBCT) plays an increasingly important role in image-guided radiation therapy. However, the image quality of CBCT is severely degraded by excessive scatter contamination, especially in the abdominal region, hindering its further applications in radiation therapy. To restore low-quality CBCT images contaminated by scatter signals, a scatter correction algorithm combining the advantages of convolutional neural networks (CNN) and Swin Transformer is proposed. In this paper a scatter correction model for CBCT image, the Flip Swin Transformer U-shape network (FSTUNet) model, is proposed. In this model, the advantages of CNN in texture detail and Swin Transformer in global correlation are used to accurately extract shallow and deep features, respectively. Instead of using the original Swin Transformer tandem structure, we build the Flip Swin Transformer Block to achieve a more powerful inter-window association extraction. The validity and clinical relevance of the method is demonstrated through extensive experiments on a Monte Carlo (MC) simulation dataset and frequency split dataset generated by a validated method, respectively. Experimental results on the MC simulated dataset show that the root mean square error of images corrected by the method is reduced from over 100 HU to about 7 HU. Both the structural similarity index measure (SSIM) and the universal quality index (UQI) are close to 1. Experimental results on the frequency split dataset demonstrate that the method not only corrects shading artifacts but also exhibits a high degree of structural consistency. In addition, comparison experiments show that FSTUNet outperforms UNet, Deep Residual Convolutional Neural Network (DRCNN), DSENet, Pix2pixGAN, and 3DUnet methods in both qualitative and quantitative metrics. Accurately capturing the features at different levels is greatly beneficial for reconstructing high-quality scatter-free images. The proposed FSTUNet method is an effective solution to CBCT scatter correction and has the potential to improve the accuracy of CBCT image-guided radiation therapy.

Toward commercialization with lightweight, flexible perovskite solar cells for residential photovoltaics

Metal-halide perovskites have emerged as a promising class of next-generation solar cells. Here, we assess what lifetimes and efficiencies perovskite solar cells (PSCs) have to reach to lower the price of commercial residential photovoltaics (PVs) further. We find that using light and flexible substrates, as opposed to heavy and rigid ones, reduces the total installed system cost of PSCs, culminating in a lower balance of system (BOS) cost, as it is possible to use different mounting methods. Concretely, we analyze the scenario when the modules are directly placed onto a roof without requiring a racking system. This reduces both labor and material costs. Furthermore, it effectively lowers the necessary efficiency or lifetime of PSCs (T80 value) to achieve the same electricity cost as commercialized silicon. For 2021, we find that a rigid perovskite module with 17% efficiency would need at least 24 years to become competitive with residential-installed silicon. In comparison, a light, flexible module with the same efficiency would only need to last 19 years. In 2030, with the accordingly projected BOS costs, a 23% efficient perovskite module would need to last 24 years if rigid but only 17 years if flexible. Finally, we extend our analysis toward tandem structures with perovskite-silicon or all-perovskite tandem architectures. We find that flexible PSCs present a promising commercialization route because it can enable low manufacturing and BOS deployment costs, which opens up commercial viability at lower efficiencies or lifetimes. Metal-halide perovskites have emerged as a promising class of next-generation solar cells. Here, we assess what lifetimes and efficiencies perovskite solar cells (PSCs) have to reach to lower the price of commercial residential photovoltaics (PVs) further. We find that using light and flexible substrates, as opposed to heavy and rigid ones, reduces the total installed system cost of PSCs, culminating in a lower balance of system (BOS) cost, as it is possible to use different mounting methods. Concretely, we analyze the scenario when the modules are directly placed onto a roof without requiring a racking system. This reduces both labor and material costs. Furthermore, it effectively lowers the necessary efficiency or lifetime of PSCs (T80 value) to achieve the same electricity cost as commercialized silicon. For 2021, we find that a rigid perovskite module with 17% efficiency would need at least 24 years to become competitive with residential-installed silicon. In comparison, a light, flexible module with the same efficiency would only need to last 19 years. In 2030, with the accordingly projected BOS costs, a 23% efficient perovskite module would need to last 24 years if rigid but only 17 years if flexible. Finally, we extend our analysis toward tandem structures with perovskite-silicon or all-perovskite tandem architectures. We find that flexible PSCs present a promising commercialization route because it can enable low manufacturing and BOS deployment costs, which opens up commercial viability at lower efficiencies or lifetimes.

A numerical analysis of ZnTe/AZO as tunnel junction in CdTe/Si tandem solar cell

Recently, interest has shifted towards developing multijunction or tandem solar cells due to their high potential to generate higher efficiency than traditional single-junction solar cells. Cadmium telluride (CdTe) and silicon (Si) solar cell materials have demonstrated significant potential in photovoltaic energy generation as tandem structures if fully developed. One approach for optimising CdTe/Si is to develop an effective tunnel junction that can electrically and optically interconnect the cadmium telluride and silicon cells with minimal loss. The wxAMPS 3.0 numerical simulation was used in this work to develop CdTe/Si tandem using zinc telluride/aluminium doped zinc oxide (ZnTe/AZO) as a tunnel junction (TJ). The result obtained shows an optimum efficiency of over 36 % with Voc = 1.945 V, Jsc = 21.519 mA/cm2, and FF = 86.823 % utilising the optimal 200 nm CdTe and Si absorber thickness of 300 μm. An analysis of the demonstrated results suggests that ZnTe/AZO tunnel junction will significantly contribute to the realisation of the CdTe/Si tandem solar cell. Hence, upon inserting a 40 nm highly doped ZnTe/AZO tunnelling junction to a CdTe/Si tandem configuration, the solar cell’s performance was enhanced by 48.190%.

Device Optimization of a Pb-Free All Perovskite Tandem Solar Cell with 29.59% Power Conversion Efficiency

This study has focused on simulating a highly efficient lead-free all-perovskite tandem solar cell using the SCAPS 1D device simulation tool. In the tandem structure, the top cell used Cs2AgBi0.75Sb0.25Br6 (Eg = 1.80 eV), and the bottom cell used FAMASnGeI3 (Eg = 1.40 eV) as the absorber material. Also, ZnO and NiOx were used as the electron transport layer (ETL) and the hole transport layer (HTL), respectively. Primarily the individual top cell and bottom cell have been optimized. The highest efficiency of the top cell was found to be 17.13% with performance parameters VOC = 1.23V, JSC = 15.57 mA/cm2 and FF = 89.39%, whereas the optimized efficiency of the bottom cell was found to be 17.58% with performance parameters VOC = 0.85V, JSC= 27.38 mA/cm2 and FF = 75.34%. The thickness of the absorber of the top cell and bottom cell shows a significant impact on the device performance and the optimum thickness for the Cs2AgBi0.75Sb0.25Br6 absorber layer was found to be 400 nm, whereas for the FAMASnGeI3 layer was found to be 200 nm. Careful optimization of the tandem device has resulted in an improvement of the performance and obtained an efficiency of 29.59 %, with JSC of 17.50 mA/cm2, VOC of 2.09 V, and FF of 80.87%. The final simulated device sums up tremendous potential for the fabrication of a highly efficient PSC device using lead-free perovskite materials towards excelling commercialization.

Numerical Method for Calculation of Power Conversion Efficiency and Colorimetrics of Rectangular Luminescent Solar Concentrators

Similar to conventional photovoltaics, the path toward higher efficiencies for luminescent solar concentrators (LSCs) shows increased interest in tandem structures. Herein, a numerical calculation that allows for much faster estimates of fundamental LSC performance indicators (power conversion efficiency, average visible transmission, and color‐rendering index) compared to ray trace simulations is proposed. Both double and triple structures are assessed, taking into account concentrations, absorption and emission spectra, and quantum yield as luminophore inputs for rectangular LSCs of any size. The waveguide material is modeled using an absorption spectrum and a refractive index. Interactions between the first, second, and/or third LSCs are incorporated into the algorithm. A comparison with ray trace results shows good correspondence. Supplementary Excel files are available with detailed calculations for future research or industry applications.

Genomic insight into the salt tolerance and proteolytic activity of Bacillus subtilis.

We assessed the salt tolerance and proteolytic activity of 40 genome-published Bacillus subtilis strains isolated from fermented Korean foods to illuminate the genomic background behind the functionality of B. subtilis in high-salt fermentation. On the basis of the salt tolerance and phenotypic proteolytic activity of the 40 strains, we selected five strains exhibiting different phenotypic characteristics. Comparative genomic analyses of these five strains provided genomic insight into the salt tolerance and proteolytic activity of B. subtilis. Two-component system (TCS) genes annotated as ybdGJK and laterally acquired authentic ATP-binding cassette (ABC) transporter system genes of tandem repeat structure might contribute to increase salt tolerance. The additional possession of gene homologs for CAAX protease family proteins and components of Clp (caseinolytic protease) complex, ATP-dependent Clp proteolytic subunit ClpP and AAA+ (ATPases Associated with diverse cellular Activities) family ATPases, might determine the proteolytic activity of B. subtilis. This study established the scientific foundation for the viability and functionality of B. subtilis in high-salt fermentation.

In-situ synthesis of novel dual S-scheme AgI/Ag6Mo7O24/g-C3N4 heterojunctions with tandem structure for photocatalytic degradation of organic pollutants

The controllable design of multivariate heterojunction with sequential structures is of significant relevance for breaking the performance limit of binary composite photocatalysts. In this work, the novel dual S-scheme ternary-component AgI/Ag6Mo7O24/exfoliated g-C3N4 (ECN) composite was prepared by a two-step in-situ synthetic strategy. The energy band bending at the heterointerface and the formation of dual built-in electric field could be observed due to distinct work functions of different components in the ternary composite. Benefiting from the sequential heterojunction structure, the AgI/Ag6Mo7O24/ECN composite achieved 98.7% removal efficiency of 2-nitrophenol (2-NP) within 70 min under visible light irradiation, and AgI/Ag6Mo7O24/ECN also showed higher degradation efficiency for a variety of organic pollutants such as methylene blue (MB), rhodamine B (RhB), methyl orange (MO), 4-nitrophenol (4-NP), 2-sec-butyl-4,6-dinitrophenol (DNBP) and tetracycline (TC). Notably, •OH and •O2− played dominant roles in the AgI/Ag6Mo7O24/ECN set up, which was consistent with the dual S-scheme charge transfer mechanism. In-depth insights for the photodegradation of 2-NP were presented based on a combined DFT study and GC-MS analysis. Additionally, the photoreduction of Ag+ in AgI/Ag6Mo7O24/ECN was also evaded by the fast transfer of photogenerated electrons through the dual S-scheme pathway, achieving the effect of killing two birds with one stone.

Optically and Electrically Controllable Light-Emitting Nonvolatile Resistive Switching Memory

Resistive switching memory (RSM) emerges as a decisive player for the future development of semiconductor industry due to its many advantages, such as high speed, cost effectiveness, excellent scalability, and compatibility with current technology. However, the electrical reading of the RSM array is usually in series sequence, which limits its maximum data storage density and processing speed. This drawback can be overcome by optically readable memory devices. Herein, we demonstrate an unprecedented optically and electrically controllable light-emitting RSM. This device uses a tandem structure which is composed of a light-emitting RSM and a perovskite solar cell. The state of the device can be encoded both electrically and optically, with high-resistive state and low-resistive state. Interestingly, the device exhibits electroluminescence in the low-resistive state, which provides the capability for reading the encoded signal optically. By integrating with a solar cell, the whole device enables to assist on the light-emitting RSM to achieve the unique feature of optical writing. Compared with conventional memory, our designed device with multiple functionalities of optical/electrical encoding and electrical/optical reading should be very useful and timely for the development of next-generation information technology.