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Abstract Quantum dot sensitized solar cells (QDSCs) represent a promising third‐generation photovoltaic technology, boasting a high theoretical efficiency of 44% and cost efficiency. However, their practical efficiency is constrained by reduced photovoltage (Voc) and fill factor (FF). One primary reason is the inefficient charge transfer and elevated recombination rates at the counter electrode (CE). In this work, a novel CE composed of a titanium mesh loaded with Co,N─C@MoS2 is introduced for the assembly of QDSCs. The incorporation of nanosized MoS2 enhances the density of catalytic sites, while the Co,N─C component ensures high conductivity and provides a substantial active surface area. Additionally, the titanium mesh's 3D structure serves as an effective electrical conduit, facilitating rapid electron transfer from the external circuit to the composite. These improvements in catalytic activity, charge transfer rate, and stability of the CE significantly enhance the photovoltaic performance of QDSCs. The optimized cells achieve a groundbreaking power conversion efficiency (PCE) of 16.39%, accompanied by a short‐circuit current density (Jsc) of 27.26 mA cm−2, Voc of 0.818 V, and FF of 0.735. These results not only offer a new strategy for designing electrodes with high catalytic activity but also underscore the promising application of the Co,N─C@MoS2 composite in enhancing QDSC technology.

Background The study aimed to observe the internal structure of coconuts from two locations (coastal and non-coastal) using computed tomography (CT). Methods Seventy-six mature coconuts were collected from Wenchang and Ding’an cities in Hainan Province. These coconuts were scanned four times using CT, with a two-week interval between each scan. CT data were post-processed to reconstruct two-dimensional slices and three-dimensional models. The density and morphological parameters of coconut structures were measured, and the differences in these characteristics between the two groups and the changes over time were analyzed. Results Time and location had interactive effects on CT values of embryos, solid endosperms and mesocarps, morphological information such as major axis of coconut, thickness of mesocarp, volume of coconut water and height of bud (p

Abstract How to improve the capacity of light‐harvesting is still an important point and essential strategy for the assembling of high‐efficiency quantum dot–sensitized solar cells (QDSCs). A believable approach is to implant new light absorption materials into QDSCs to stimulate the charge transfer. Herein, the few‐layer black phosphorus quantum dots (BPQDs) are synthesized by electrochemical intercalation technology using bulk BP as source. Then the obtained BPQDs are deposited onto the surface of Zn–Cu–In–S–Se (ZCISSe) QD‐sensitized TiO2 substrate to serve as another light‐harvesting material for the first time. The experimental results have shown that BPQDs can not only increase the absorption intensity by photoanode but also reduce unnecessary charge recombination processes at the interface of photoanode/electrolyte. Through optimizing the size and deposition process of BPQDs, the champion power conversion efficiency of ZCISSe QDSCs is increased to 15.66% (26.88 mA/cm2, Voc = 0.816 V, fill factor [FF] = 0.714) when compared with the original value of 14.11% (Jsc = 25.41 mA/cm2, Voc = 0.779 V, FF = 0.713).

Two-dimensional transition metal dichalcogenides (2DTMDs) and their van der Waals heterojunctions (vdWHs) have garnered significant attention working as the channel material of optoelectronics. The development of new heterojunction growth schemes may also provide better performance for optoelectronic devices. In this paper, PtSe2 thin films with controllable size and thickness are directly grown on MoS2 nanosheet by sputtering-selenization two-step growth method. The photodetector with PtSe2/MoS2 heterojunction exhibits a type-I band alignment and leads to an impressive broadband spectral photoresponse (405 to 1550 nm). It can achieve responsivity as high as 5.42 A/W, a detectivity of 2.52 × 1010 Jones, and a fast response rate (92/112 μs for rise/fall time respectively). In addition, the device has excellent stability in the air atmosphere and keeps its photoresponse after even six months. The in-situ growth method provides a new scheme to construct heterojunctions of 2DTMDs and develop energy-efficient photodetectors with enhanced performance. It also supplements the practical production and application of large-scale broadband detectors.

Structural engineering is crucial for tuning the properties of artificial materials. As one of the most important two-dimensional (2D) materials, black phosphorus (BP) has been rediscovered in 2014 and attracted tremendous attentions all over the world. It shows great potentials in optoelectronic and integrated photonic applications due to the direct and tunable bandgap, high carrier mobility, and intrinsic anisotropy. However, some deficiencies are yet to be settled before its large-scale applications, such as the massive synthesis methods and structure–property relationship. To investigate the influence of structural engineering on the performance of 2D BP-based devices thoroughly, recent studies on deformation, atomic defects, superlattice, alloying, thickness and phase transition are maximality summarized in this review covering from the intrinsic properties to optoelectronic applications. Benefiting from the broad research in this field, challenges and opportunities of 2D BP for advanced integrated photonic applications are also provided, which supplies a useful reference to realize large-scale 2D BP-based all-optical communications in future.

Due to the unique structure of coconuts, their cultivation heavily relies on manual experience, making it difficult to accurately and timely observe their internal characteristics. This limitation severely hinders the optimization of coconut breeding. To address this issue, we propose a new model based on the improved architecture of Deeplab V3+. We replace the original ASPP(Atrous Spatial Pyramid Pooling) structure with a dense atrous spatial pyramid pooling module and introduce CBAM(Convolutional Block Attention Module). This approach resolves the issue of information loss due to sparse sampling and effectively captures global features. Additionally, we embed a RRM(residual refinement module) after the output level of the decoder to optimize boundary information between organs. Multiple model comparisons and ablation experiments are conducted, demonstrating that the improved segmentation algorithm achieves higher accuracy when dealing with diverse coconut organ CT(Computed Tomography) images. Our work provides a new solution for accurately segmenting internal coconut organs, which facilitates scientific decision-making for coconut researchers at different stages of growth.

Neuromorphic optoelectronic sensors with in-sensor computing architecture hold great promise for applications that require processing large amounts of redundant data, such as the Internet of Things, robotics, and environmental sciences, due to their advantages of low time latency and energy efficiency. Halide perovskites, known for their extraordinary optoelectronic properties and stimuli-responsive characteristics, offer excellent opportunities for developing switchable visual sensors with high sensitivity, fast response, low energy consumption, and wide adaptive range. In this work, we successfully realized a MAPbBr3-PdSe2 heterojunction-based optoelectronic sensor, demonstrating a responsivity of 28 mA/W and a high specific detectivity of 5.2 × 1011 Jones. A fast response time of ∼ 25 μs has also been achieved. Additionally, we investigated the role of voltage-induced ion migration in actively adjusting the device's photoresponse capacity. Under 0 V bias, the device exhibited a wide switchable range of optical responsivity from 137.5% to 27000%, significantly surpassing pure perovskite-based devices in previous reports. Moreover, we demonstrated the device's adaptive learning capabilities and reproducible switching characteristics by simulating Pavlovian classical conditioned reflex experiments using electrical modulation. These findings open up exciting possibilities for next-generation artificial vision systems that are energy-efficient, adaptive, and capable of learning and effectively responding to varying visual conditions.

Many of the most sensitive X-ray detectors are based on toxic elements such as lead, limiting their safe applications. Here, the authors report the realization of sensitive X-ray detectors based on solution-grown thick BiI/BiI3/BiI van der Waals heterostructures, showing a detection limit down to 34 nGy s−1 and high stability.

Abstract Background As one of the largest drupes in the world, the coconut has a special multilayered structure and a seed development process that is not yet fully understood. On the one hand, the special structure of the coconut pericarp prevents the development of external damage to the coconut fruit, and on the other hand, the thickness of the coconut shell makes it difficult to observe the development of bacteria inside it. In addition, coconut takes about 1 year to progress from pollination to maturity. During the long development process, coconut development is vulnerable to natural disasters, cold waves, typhoons, etc. Therefore, nondestructive observation of the internal development process remains a highly important and challenging task. In this study, We proposed an intelligent system for building a three-dimensional (3D) quantitative imaging model of coconut fruit using Computed Tomography (CT) images. Cross-sectional images of coconut fruit were obtained by spiral CT scanning. Then a point cloud model was built by extracting 3D coordinate data and RGB values. The point cloud model was denoised using the cluster denoising method. Finally, a 3D quantitative model of a coconut fruit was established. Results The innovations of this work are as follows. 1) Using CT scans, we obtained a total of 37,950 non-destructive internal growth change maps of various types of coconuts to establish a coconut data set called “CCID”, which provides powerful graphical data support for coconut research. 2) Based on this data set, we built a coconut intelligence system. By inputting a batch of coconut images into a 3D point cloud map, the internal structure information can be ascertained, the entire contour can be drawn and rendered according to need, and the long diameter, short diameter and volume of the required structure can be obtained. We maintained quantitative observation on a batch of local Hainan coconuts for more than 3 months. With 40 coconuts as test cases, the high accuracy of the model generated by the system is proven. The system has a good application value and broad popularization prospects in the cultivation and optimization of coconut fruit. Conclusion The evaluation results show that the 3D quantitative imaging model has high accuracy in capturing the internal development process of coconut fruits. The system can effectively assist growers in internal developmental observations and in structural data acquisition from coconut, thus providing decision-making support for improving the cultivation conditions of coconuts.

The low-energy electronic excitations in topological semimetal yield a plethora of a range of novel physical properties. As a relatively scarce branch, the research of triple-degenerate semi-metal is mostly confined to the stage of physical properties and theoretical analysis, there are still challenges in its practical application. This research showcases the first application of the triply degenerate semimetal PtBi _2 in electronic devices. Leveraging a van der Waals transfer method, PtBi _2 flakes were used as interlayer contacts for metal electrodes and WS _2 in transistors. The transistor achieved a switching ratio above 10 ^6 and average mobility can reach 85 cm ^2 V ^−1 s ^−1 , meeting integrated circuit requirements. Notably, the excellent air stability of PtBi _2 simplifies the device preparation process and provides more stable device performance. Transfer process reduces the Schottky barrier between metal electrodes and semiconductors while avoiding Fermi pinning during metal deposition to achieve excellent contact. This groundbreaking work demonstrates the practical applicability of PtBi _2 in the field of electronic devices while opening new avenues for the integration of novel materials in semiconductor technology, setting a precedent for future innovations.

Heterojunction photodetectors based on 2D materials are a promising geometry to acquire broadband photodetection with combination of wide-bandgap and narrow bandgap functional materials. But the interface condition of the heterojunction is difficult to control due to the inevitable introduction of air bubbles and wrinkles. In this paper, a synthesis method merging exfoliation and CVD is reported to fabricate photodetectors of the GaSe/PtSe2 heterojunction. The devices present the highest responsivity and detectivity of about 1.7 A/W and 3.51 × 1012 Jones at a −10 V bias under the avalanche mode, respectively. Also, a fast response time could be obtained around 20 μs. In addition, the photodetector exhibits a clear photovoltaic effect, which can work in a self-powered mode.

As a typical representative of group III-VI two-dimensional (2D) layered semiconductors, α-In2Se3 with layer-dependent direct bandgap (1.39–1.45 eV) has attracted great attention in optoelectronics. At present, various α-In2Se3 based photodetectors have been developed, which show ultrahigh responsivity and detectivity at visible (VIS) wavelengths. However, despite the high sensitivity, the response time is quite long, and the realization of broadband detection from VIS to infra-red (IR) wavelengths is also challenging for these α-In2Se3 photodetectors. In this paper, we introduced a narrow and direct bandgap 2D semiconductor Ta2NiSe5 and made an α-In2Se3/Ta2NiSe5 heterojunction photodetector, which achieved a wide response wavelength of 405–1550 nm with high performance. Originating from the n-type nature of the two semiconductors and the particular type-I energy band alignment, the potential barriers of holes at the α-In2Se3/Ta2NiSe5 interface is much higher than that of electrons, which leads to an ultra-high responsivity. At 520 nm illumination, the photoresponsivity is 12 A/W and 533 A/W under a self-driven state and a slight bias voltage of 0.1 V, respectively. The highest detectivity is over 8.2 × 1013 Jones. Furthermore, the rise and fall time is shortly at 25 and 423 μs, respectively. We believe that the high-sensitive, broadband, and fast photodetector has great potential in the emerging field of 2D optoelectronics.

IntroductionComputed tomography (CT) is a non-invasive examination tool that is widely used in medicine. In this study, we explored its value in visualizing and quantifying coconut.Materials and methodsTwelve coconuts were scanned using CT for three months. Axial CT images of the coconuts were obtained using a dual-source CT scanner. In postprocessing process, various three-dimensional models were created by volume rendering (VR), and the plane sections of different angles were obtained through multiplanar reformation (MPR). The morphological parameters and the CT values of the exocarp, mesocarp, endocarp, embryo, bud, solid endosperm, liquid endosperm, and coconut apple were measured. The analysis of variances was used for temporal repeated measures and linear and non-linear regressions were used to analyze the relationship between the data.ResultsThe MPR images and VR models provide excellent visualization of the different structures of the coconut. The statistical results showed that the weight of coconut and liquid endosperm volume decreased significantly during the three months, while the CT value of coconut apple decreased slightly. We observed a complete germination of a coconut, its data showed a significant negative correlation between the CT value of the bud and the liquid endosperm volume (y = -2.6955x + 244.91; R2 = 0.9859), and a strong positive correlation between the height and CT value of the bud (y = 1.9576 ln(x) -2.1655; R2 = 0.9691).ConclusionCT technology can be used for visualization and quantitative analysis of the internal structure of the coconut, and some morphological changes and composition changes of the coconut during the germination process were observed during the three-month experiment. Therefore, CT is a potential tool for analyzing coconuts.

Abstract Large‐scale production of two‐dimensional (2D) materials still is a crucial point toward its practical applications. Violet phosphorus (VP) with a wide bandgap accelerates and broadens the potential applications of elemental phosphorus in optoelectronics. Here, we demonstrate the scalable production of solution‐processable violet phosphorus flakes stably dispersed in several solvents. The exfoliated VP flakes exhibit thickness‐dependent visible photoluminescence characteristics, which covers the shortcoming of black phosphorus. Meanwhile, the VP‐based field‐effect transistor reveals relatively competitive electrical properties to other liquid‐phase exfoliated 2D materials. Our study paves the way for a wide range of applications of optical devices, energy storage, catalysis, and sodium batteries based on large‐scale VP flakes.

With the rapid demand growth of green energy technologies, solar cell has been considered as a very promising technology to address current energy and environmental issues. Among them, perovskite solar cells (PSCs) have attracted much research interest in recent years due to the prominent advantages of light weight, good flexibility, low cost, and comparable power conversion efficiency (PCE) to that of traditional commercial solar cells (ie, amorphous silicon, GaAs, and CdTe). Meanwhile, elemental two-dimensional (2D) graphene and its derivatives, which possess the outstanding advantages of abundant functional groups, good environmental stability, and good compactness, have been extensively studied on the integration with PSC devices. The review introduces the properties and preparation methods of graphene and its derivatives, and the applications in PSC are summarized in detail. Ultimately, the critical challenges and prospects for the further development of graphene and its derivatives in PSCs are discussed.

Recently, n-n junction with large bandgap offset has been reported to be able to realize rectifier function and improve photoresponse in optoelectronic applications. In this work, we demonstrate a simple way to engineer photodetector based on a MoSe2/ZnO heterojunction. ZnO thin film deposited by DC magnetron sputtering and mechanically exfoliated MoSe2 was coupled to form vertical stacking heterostructure. An atomically sharp n-n junction with type-II band alignment and current rectification behaviour is realised. The MoSe2/ZnO based photodetector exhibits a fast photoresponse speed of 40 μs, and a peak responsivity of 2.7 A/W. It is also demonstrated that the MoSe2/ZnO photodiode can operate under self-powered mode over a broad spectrum.

Broadband photodetectors have attracted substantial attention in recent years. The ternary chalcogenide Ta2NiSe5 is a layered material with a direct narrow-band gap (Eg ~ 0.33 eV) which possesses greatly potential to broadband photodetectors. Here, high-quality bulk Ta2NiSe5 was synthesized by Chemical Vapor Transport (CVT) method. We demonstrate a photodetector based on exfoliated Ta2NiSe5 nanoflake, which exhibits a broadband photo-response from 405 nm to 4300 nm. Meanwhile, its main characteristics are superior to other typical 2D materials: high responsivity ~198.1 A W−1 at 1350 nm and ultrafast response time of ~27.4 µs. Long-time photocurrent reproducibility shows that the photodetector has excellent stability under atmosphere. Furthermore, the scanning photocurrent mapping reveals the photoconductive mechanism of Ta2NiSe5 photodetector. In addition, the anisotropic ratio of the photocurrent is ~1.46. The broadband photodetection, high responsivity, anisotropic and environmental stability achieved simultaneously in Ta2NiSe5 photodetector, which are promising for neotype electronics and optoelectronics field.

Organic semiconductors have been proven as emerging platforms for exploring strong light–matter interactions and quantum optics so as to develop coherent and quantum photonic devices. Though there has been abundant research on organic semiconductors, lasing action is rarely reported in individual 2D organic semiconductor waveguides or nanocavities. Herein, a strong optical waveguiding phenomenon is observed not only in the individual 2D organic semiconductor Znq2 nanosheet with micrometer size area, but also in the interconnecting or neighboring Znq2 nanosheets. The optical propagation loss coefficient of the interconnecting Znq2 sheets is ≈800 dB cm−1. More importantly, the phenomenon of optically pumped lasing in 2D Znq2 nanosheets is demonstrated, as evidenced by a sudden increase in emission intensity at a threshold pump pulse fluence of 49.9 W cm−2 at 480 nm. As verified by numerical FDTD simulations, the Znq2 nanosheet constitutes a microcavity that supports whisper gallery mode, providing suffcient feedback for laser oscillations. Herein, the coexistence of low‐loss waveguiding and excellent lasing in 2D organic semiconductor nanosheets are revealed, which open up a new pathway for photonics and quantum optics based on 2D organic semiconductors.

Lithium sulfur batteries are promising for next-generation energy storage, but are hindered by polysulfide shuttle effects. Here the authors use black phosphorus quantum dots to adsorb and catalyze the conversion of lithium polysulfides to lithium sulfide, achieving low capacity fade and high sulfur loading.

In recent years, polaritons in two-dimensional (2D) materials have gained intensive research interests and significant progress due to their extraordinary properties of light-confinement, tunable carrier concentrations by gating and low loss absorption that leads to long polariton lifetimes. With additional advantages of biocompatibility, label-free, chemical identification of biomolecules through their vibrational fingerprints, graphene and related 2D materials can be adapted as excellent platforms for future polaritonic biosensor applications. Extreme spatial light confinement in 2D materials based polaritons supports atto-molar concentration or single molecule detection. In this article, we will review the state-of-the-art infrared polaritonic-based biosensors. We first discuss the concept of polaritons, then the biosensing properties of polaritons on various 2D materials, then lastly the impending applications and future opportunities of infrared polaritonic biosensors for medical and healthcare applications.

Though there have been many investigations focusing on organic semiconductors, how to fully probe their waveguiding properties is still rarely reported. In this work, the light propagation loss in the Znq _2 samples was detected by a modified light transmission path. The results showed that the optical propagation loss coefficient of Znq _2 nanorods is ∼0.16 dB μ m ^−1 . Our work fully reveals the waveguiding properties in 2D organic semiconductor by 2D & 3D imaging, which may offer a new reference for exploring novel optical properties of 2D organic semiconductors.

First-principles calculation is employed to investigate atomic and electronic properties of Ge/SiC heterojunction with different Ge orientations. Based on the density functional theory, the work of adhesion, relaxation energy, density of states, and total charge density are calculated. It is shown that Ge(110)/4H-SiC(0001) heterointerface possesses higher adhesion energy than that of Ge(111)/4H-SiC(0001) interface, and hence Ge/4H-SiC(0001) heterojunction with Ge[110] crystalline orientation exhibits more stable characteristics. The relaxation energy of Ge(110)/4H-SiC(0001) heterojunction interface is lower than that of Ge(111)/4H-SiC(0001) interface, indicating that Ge(110)/4H-SiC(0001) interface is easier to form at relative low temperature. The interfacial bonding is analysed using partial density of states and total charge density distribution, and the results show that the bonding is contributed by the Ge-Si bonding.

Raman spectroscopy was applied to different-impurities-doped 6H-SiC crystals. It had been found that the first-order Raman spectra of N-, Al- and B-doped 6H-SiC were shifted to higher frequency when comparing with undoped samples. However, the first-order Raman spectra of V-doped sample was shifted to lower frequency, revealing that there existed low free carrier concentration, which might be induced by the deep energy level effect of V impurity. Meanwhile, the second-order Raman spectra are independent of polytype and impurity type.