Development of an automatic monitoring system for rice light-trap pests based on machine vision

Monitring pest populations in paddy fields is important to effectively implement integrated pest management.Light traps are widely used to monitor field pests all over the world.Most conventional light traps still involve manual identification of target pests from lots of trapped insects,which is time-consuming,labor-intensive and error-prone,especially in pest peak periods.In this paper,we developed an automatic monitoring system for rice light-trap pests based on machine vision.This system is composed of an itelligent light trap,a computer or mobile phone client platform and a cloud server.The light trap firstly traps,kills and disperses insects,then collects images of trapped insects and sends each image to the cloud server.Five target pests in images are automatically identifed and counted by pest identification models loaded in the server.To avoid light-trap insects piling up,a vibration plate and a moving rotation conveyor belt are adopted to disperse these trapped insects.There was a close correlation(r=0.92)between our automatic and manual identification methods based on the daily pest number of one-year images from one light trap.Field experiments demonstrated the effectiveness and accuracy of our automatic light trap monitoring system.

Light trapping characteristics of glass substrate with hemisphere pit arrays in thin film Si solar cells

In this paper, the light trapping characteristics of glass substrate with hemisphere pit （HP） arrays in thin film Si solar cells are theoretically studied via a numerical approach. It is found that the HP glass substrate has good antireflection properties. Its surface reflectance can be reduced by - 50% compared with planar glass. The HP arrays can make the unabsorbed light return to the absorbing layer of solar cells, and the ratio of second absorption approximately equals 30%. Thus, the glass substrate with the hemisphere pit arrays （HP glass） can effectively reduce the total reflectivity of a solar celt from 20% to 13%. The lip glass can also prolong the optical path length. The numerical results show that the total optical path length of the thin film Si solar cell covered with the HP glass increases from 2ω to 409. These results are basically consistent with the experimental results.

Improving light trapping and conversion efficiency of amorphous silicon solar cell by modified and randomly distributed ZnO nanorods

Three-dimensional （3D） nanostructures in thin film solar cells have attracted significant attention due to their appli- cations in enhancing light trapping. Enhanced light trapping can result in more effective absorption in solar cells, thus leading to higher short-circuit current density and conversion efficiency. We develop randomly distributed and modified ZnO nanorods, which are designed and fabricated by the following processes： the deposition of a ZnO seed layer on sub- strate with sputtering, the wet chemical etching of the seed layer to form isolated islands for nanorod growth, the chemical bath deposition of the ZnO nanorods, and the sputtering deposition of a thin Al-doped ZnO （ZnO：Al） layer to improve the ZnO/Si interface. Solar cells employing the modified ZnO nanorod substrate show a considerable increase in solar energy conversion efficiency.

Beyond Lambertian light trapping for large-area silicon solar cells:fabrication methods

Light trapping photonic crystal(PhC)patterns on the surface of Si solar cells provides a novel opportunity to approach the theoretical efficiency limit of 32.3%,for light-to-electrical power conversion with a single junction cell.This is beyond the efficiency limit implied by the Lambertian limit of ray trapping~29%.The interference and slow light effects are harnessed for collecting light even at the long wavelengths near the Si band-gap.We compare two different methods for surface patterning,that can be extended to large area surface patterning:1)laser direct write and 2)step-&-repeat 5×reduction projection lithography.Large area throughput limitations of these methods are compared with the established elec-tron beam lithography(EBL)route,which is conventionally utilised but much slower than the presented methods.Spec-tral characterisation of the PhC light trapping is compared for samples fabricated by different methods.Reflectance of Si etched via laser patterned mask was~7%at visible wavelengths and was comparable with Si patterned via EBL made mask.The later pattern showed a stronger absorbance than the Lambertian limit6.

Comparative Human Landing Catch and CDC Light Trap in Mosquito Sampling in Knowlesi Malaria Endemic Areas in Peninsula Malaysia

Adult mosquito sampling techniques are essential for monitoring transmission of malaria and other mosquito borne infections. Preference for any sampling technique depends on both its field efficiency and the characteristics of local vector populations. Surveys on adult mosquitoes using Human Landing Catch (HLC) and CO2-baited CDC light trap (CDC-LT) techniques were conducted in several knowlesi malaria endemic areas between the months of March to December 2012 in several states of Peninsula Malaysia. These two techniques were relatively compared to determine the preferences of anopheline mosquitoes towards CO2-baited CDC-LT technique using HLC technique as the reference method. Cx. gelidus, An. maculates and An. introlatus were the main three species collected by HLC technique, whereas the species collected by CO2-baited CDC-LT technique were mostly An. cracens, Ar. durhami and Coquillettidia species. Most of the Anopheles species were collected almost exclusively by the human collectors except for An. cracens and An. introlatus which were collected using both techniques. Anopheles cracens was the most dominant species captured using CO2-baited CDC-LT technique. This is the first report showing An. cracens was caught using CO2-baited CDC-LT technique in Malaysia.

The Role of Mineral and Natural Oils in Integration with Inorganic Salts and Some Insecticides in Suppressing the Invasion of the Red Palm Weevil Rhynchophorus ferrugineus (RPW) Affecting Date Palms with Estimation of Its Residues in the Resulting Date Fruits

Applied experiments were conducted in the palm orchard in the Nubaria region. The orchard includes the varieties of Al-Barhi (imported) and Zaghloul (local) to examine the efficacy of some natural materials alone and in combination with some pesticides against the Red Palm Weevil Rhynchophorus ferrugineus (RPW) that infects palm trees in Egypt. Most insects caught by light traps, which have a role in the spread of the red palm weevil in palm groves, appear in early February and March. Peak numbers for the month of May until September namely Phyllgnathus excavatus. Pseudophilus testaceus, Phonapata frontalis, and Oryctes elegans. The neglected gardens of date palms are more compensating for insect infestation than those maintained in terms of agricultural and pest control services. Individual injection of insecticide (Mosspilan) was the most potent against RPW-infested Barhi var. with a recovery rate of 91.7%, followed by Selikron at 80%, and finally Saydon at 37.5%. Injection of the car oil used with Mosspilan followed by Selikron was effective against RPW. No significant difference between treatments of injection (F-value: 1.2). Mixing injection of mineral oils with chemical pesticides is effective against red palm weevil after two successive seasons. As a result, the pesticide was poured around the affected palm root, with a low recovery rate. There is no effect of palm spray. The best way to control the red palm weevil is the method of injecting the tested material (single or mixed) with the pure pesticide into the trunk of the infected palm tree. The tested pesticide residues gradually decrease as the period after application is prolonged with an average loss of 0.12, 0.02 and 0.07 ppm after 90 consecutive days. .

Invertebrates Diversity in Arabuko-Sokoke Forest and Nearby Farm­land at Gede,Kilifi County,Kenya

Insectivorous bats mainly feed on various types of invertebrates.The authors studied the abundance and diversity of invertebrates in the farmland in the eastern part of Arabuko-Sokoke Forest,mainly to assess their availability to insectivorous bats occurring in the two study sites.Solar powered light traps were used to attract aerial invertebrates to a white suspended cloth sheet used as a landing surface.The sampling was conducted for four hours in one trapping station each night,and in twelve different stations both in the ASF and farmland.A total of 6,557 invertebrates individuals were trapped,which included 48%in ASF and 52%in the farmland.The two most common invertebrate orders were Hymenoptera(ants,bees,wasps and sawflies)represented by 38.1%,and Coleoptera(beetles,28.1%).The interior of ASF had higher invertebrate species diversity(Shannon-Weiner index 1.72±0.1),than the farmland(1.41±0.1).Although the farmland(260.5±52.9,N=12)had higher mean number of invertebrates trapped per night,than the interior of ASF(200.3±36.4,N=12),there was no significant difference between the medians of invertebrates captured in the two study areas(Mann-Whitney U-Test,U=61:P>0.544).Thus,the farmland and the interior of ASF had the same invertebrate abundance.This study indicates the value of human-modified areas(agricultural and human settlements)landscapes,always ignored in biodiversity surveys,in sustaining diverse invertebrates that are preyed by different species of insectivorous bats that occur in the two study areas.

Analysis of phototactic responses in Spodoptera frugiperda using Helicoverpa armigera as control

Light traps are widely utilized to monitor and manage insect pest populations.In late 2018,the fall armyworm(FAW),Spodoptera frugiperda,invaded China through Yunnan Province representing a huge threat to grain production.To estimate the efficiency of light traps on FAW moths,we first identified the opsin genes from FAW by using the transcriptome.Phylogenetic analysis indicated that the four opsins of FAW were clustered with those of other Noctuidae species.The expressed levels of opsins in S.frugiperda were lower than in Helicoverpa armigera,suggesting a different phototactic response between the two species.Then,we determined the phototactic behavior of FAW using H.armigera as a control,which is widely monitored and managed using light traps in China.Our results indicated that the two moths species showed significantly different phototactic behavior and both female and male FAW displayed faster flight-to-light speed than H.armigera.This may be due to a faster flight capacity in FAW compared to H.armigera.However,the capture rate of both female and male of S.frugiperda was significantly lower than that of H.armigera,which was consistent with the expression levels of opsins.These results support the positive phototaxis of S.frugiperda moths and suggest light traps could be used for monitoring and managing the pests,but with a lower efficiency than H.armigera.

Absorption enhancement in thin film a-Si solar cells with double-sided SiO_2 particle layers

Light absorption enhancement is very important for improving the power conversion efficiency of a thin film a-Si solar cell. In this paper, a thin-film a-Si solar cell model with double-sided SiO2 particle layers is designed, and then the underlying mechanism of absorption enhancement is investigated by finite difference time domain（FDTD） simulation;finally the feasible experimental scheme for preparing the SiO2 particle layer is discussed. It is found that the top and bottom SiO2 particle layers play an important role in anti-reflection and light trapping, respectively. The light absorption of the cell with double-sided SiO2 layers greatly increases in a wavelength range of 300 nm-800 nm, and the ultimate efficiency increases more than 22% compared with that of the flat device. The cell model with double-sided SiO2 particle layers reported here can be used in varieties of thin film solar cells to further improve their performances.

Optical management in organic photovoltaic devices

Due to their potentials in light‐weight,flexible,and semitransparent devices,organic photovoltaics are of great significance in the field of renewable energy.However,the narrow intrinsic absorption spectrum of organic materials hinders the full utilization of solar energy.To fabricate a highly efficient opaque solar cell,it is greatly necessary to modify the optical properties of the device to improve light absorption.In addition,the growing interest in building‐integrated photovoltaics drives the development of semitransparent devices.The preparation of semitransparent solar cells with excellent performance imposes high requirements on the high efficiency and appropriate visible light transmittance of effective optical management.In this review,the recent research progress of optical management in organic photovoltaics is reviewed,including the design of light‐absorbing materials,the modification of different layers,adding a lighttrapping structure,and changing the light absorption capabilities of specific materials,so as to provide strategies of how to improve the performance of organic photovoltaic devices and present the prospect of the area.

Light trapping enhanced broadband photodetection and imaging based on MoSe_(2)/pyramid Si vdW heterojunction

Two-dimensional(2D)layered materials have been considered promising candidates for next-generation optoelectronics.However,the performance of 2D photodetectors still has much room for improvement due to weak light absorption of planar 2D materials and lack of high-quality heterojunction preparation technology.Notably,2D materials integrating with mature bulk semiconductors are a promising pathway to overcome this limitation and promote the practical application on optoelectronics.In this work,we present the patterned assembly of MoSe_(2)/pyramid Si mixed-dimensional van der Waals(vdW)heterojunction arrays for broadband photodetection and imaging.Benefited from the light trapping effect induced enhanced optical absorption and high-quality vdW heterojunction,the photodetector demonstrates a wide spectral response range from 265 to 1550 nm,large responsivity up to 0.67 A·W^(-1),high specific detectivity of 1.84×10^(13)Jones,and ultrafast response time of 0.34/5.6μs at 0 V.Moreover,the photodetector array exhibits outstanding broadband image sensing capability.This study offers a novel development route for high-performance and broadband photodetector array by MoSe_(2)/pyramid Si mixed-dimensional heterojunction.

ISOTROPIC TEXTURING OF POLYCRYSTALLINE SILICON WAFERS

An isotropic etching technique of texturing silicon solar cells has been applied to polycrystalline silicon wafers with different acid concentrations. Optimal e tching conditions have been determined by etching rate calculation, scanning ele ctron microscope (SEM) image and reflectance measurement. The surface morphology of the textured wafers varies in accordance with the different etchant concentr ation which in turn leads to the dissimilarity of etching speed. Textured polycr ystalline silicon wafer surfaces display randomly located etched pits which can reduce the surface reflection and enhance the light absorption. The special rela tionship between reflectivity and etching rate was studied. Reflectance measurem ents show that isotropic texturing is one of the suitable techniques for texturi ng polycrystalline silicon wafers and benefits solar cells performances.

Investigation on Open-Circuit Voltage of an Efficiency-Boosting Solar Cell Technique Featuring V-Configuration

The V-Shaped Module (VSM) solar cell technology, which breaks the traditional concept of solar cell system, has been proven to enhance power conversion efficiency of some solar cells and has offered opportunities to increase generation power densities in area-limited applications. Compared to a planar cell system, the VSM has an additional opportunity to absorb photons and taps the potential of solar cells. In this study, the VSM, the proposed common technique enhancing efficiencies of various solar cells, was investigated by using commercially available multi-crystalline silicon solar cells. The VSM technique enables the efficiencies of the multi-crystalline silicon cells to increase from 13.4% to 20.2%, giving an efficiency boost of 51%. Though the efficiency of the cells increases, the open-circuit voltage of the cells decreases owing to the VSM technique. Furthermore, the obvious reduction in open-circuit voltage in the VSM was found and the phenomenon is explained for the first time.

Metallic nanostructures for light trapping in energy-harvesting devices

Solar energy is abundant and environmentally friendly.Light trapping in solar-energy-harvesting devices or structures is of critical importance.This article reviews light trapping with metallic nanostructures for thin film solar cells and selective solar absorbers.The metallic nanostructures can either be used in reducing material thickness and device cost or in improving light absorbance and thereby improving conversion efficiency.The metallic nanostructures can contribute to light trapping by scattering and increasing the path length of light,by generating strong electromagnetic field in the active layer,or by multiple reflections/absorptions.We have also discussed the adverse effect of metallic nanostructures and how to solve these problems and take full advantage of the light-trapping effect.

Highly efficient GaAs solar cells by limiting light emission angle

In a conventional flat plate solar cell under direct sunlight,light is received from the solar disk,but is re-emitted isotropically.This isotropic emission corresponds to a significant entropy increase in the solar cell,with a corresponding drop in efficiency.Here,using a detailed balance model,we show that limiting the emission angle of a high-quality GaAs solar cell is a feasible route to achieving power conversion efficiencies above 38%with a single junction.The highest efficiencies are predicted for a thin,light trapping cell with an ideal back reflector,though the scheme is robust to a non-ideal back reflector.Comparison with a conventional planar cell geometry illustrates that limiting emission angle in a light trapping geometry not only allows for much thinner cells,but also for significantly higher overall efficiencies with an excellent rear reflector.Finally,we present ray-tracing and detailed balance analysis of two angular coupler designs,show that significant efficiency improvements are possible with these couplers,and demonstrate initial fabrication of one coupler design.

Exceeding the limit of plasmonic light trapping in textured screen-printed solar cells using Al nanoparticles and wrinkle-like graphene sheets

The solar cell market is predominantly based on textured screen-printed solar cells.Due to parasitic absorption in nanostructures,using plasmonic processes to obtain an enhancement that exceeds 2.5%of the short-circuit photocurrent density is challenging.In this paper,a 7.2%enhancement in the photocurrent density can be achieved through the integration of plasmonic Al nanoparticles and wrinkle-like graphene sheets.For the first time,we experimentally achieve Al nanoparticle-enhanced solar cells.An innovative thermal evaporation method is proposed to fabricate low-coverage Al nanoparticle arrays on solar cells.Due to the ultraviolet(UV)plasmon resonance of Al nanoparticles,the performance enhancement of the solar cells is significantly greater than that from Ag nanoparticles.Subsequently,we deposit wrinkle-like graphene sheets over the Al nanoparticle-enhanced solar cells.Compared with planar graphene sheets,the bend carbon layer also exhibits a broadband light-trapping effect.Our results exceed the limit of plasmonic light trapping in textured screen-printed silicon solar cells.

Light Trapping Effect in Wing Scales of Butterfly Papilio peranthus and Its Simulations

Broadband light trapping effect and arrays of sub-wavelength textured structures based on the butterfly wing scales are applicable to solar cells and stealth technologies. In this paper, the fine optical structures in wing scales of butterfly Papilio peranthus, exhibiting efficient light trapping effect, were carefully examined. First, the reflectivity was measured by reflectance spectrum. Field Emission Scanning Electronic Microscope （FESEM） and Transmission Electron Microscope （TEM） were used to observe the coupling morphologies and structures of the scales. Then, the optimized 3D model of the coupling structure was created combining Scanning Electron Microscope （SEM） and TEM data. Afterwards, the mechanism of the light trapping effect of these structures was analyzed by simulation and theoretical calculations. A multilayer nano-structure of chitin and air was found. These structures are effective in increasing optical path, resulting in that most of the incident light can be trapped and adsorbed within the structure at last. Furthermore, the simulated optical results are consistent with the experimental and calculated ones. This result reliably confirms that these structures induce an efficient light trapping effect. This work can be used as a reference for in-depth study on the fabrication of highly efficient bionic optical devices, such as solar cells, photo detectors, high-contrast, antiglare, and so forth.

Strongly enhanced light trapping in a two-dimensional silicon nanowire random fractal array

We report on the unconventional optical properties exhibited by a two-dimensional array of thin Si nanowires arranged in a random fractal geometry and fabricated using an inexpensive,fast and maskless process compatible with Si technology.The structure allows for a high light-trapping efficiency across the entire visible range,attaining total reflectance values as low as 0.1%when the wavelength in the medium matches the length scale of maximum heterogeneity in the system.We show that the random fractal structure of our nanowire array is responsible for a strong in-plane multiple scattering,which is related to the material refractive index fluctuations and leads to a greatly enhanced Raman scattering and a bright photoluminescence.These strong emissions are correlated on all length scales according to the refractive index fluctuations.The relevance and the perspectives of the reported results are discussed as promising for Si-based photovoltaic and photonic applications.

Plasmonic light trapping for enhanced light absorption in film-coupled ultrathin metamaterial thermophotovoltaic cells

Ultrathin cells have gained increasing attention due to their potential for reduced weight, reduced cost and increased flexibility. However, the light absorption in ultrathin cells is usually very weak compared to the corresponding bulk cells. To achieve enhanced photon absorption in ultrathin thermophotovoltaic （TPV） cells, this work proposed a film-coupled metamaterial structure made of nanometer-thick gallium antimonide （GaSh） layer sandwiched by a top one-dimensional （1D） metallic grating and a bottom metal film. The spectral normal absorptance of the proposed structure was calculated using the rigorous coupled-wave algorithm （RCWA） and the absorption enhancement was elucidated to be attributed to the excitations of magnetic polariton （MP）, surface plasmon polariton （SPP）, and Fabry-Perot （FP） resonance. The mechanisms of MP, SPP, and FP were further confirmed by an inductor-capacitor circuit model, disper- sion relation, and phase shift, respectively. Effects of grating period, width, spacer thickness, as well as incidence angle were discussed. Moreover, short-circuit current density, open-circuit voltage, output electric power,and conversion efficiency were evaluated for the ultrathin GaSb TPV cell with a film-coupled metamaterial structure. This work will facilitate the development of next- generation low-cost ultrathin infrared TPV cells.

Enhanced light trapping in periodically truncated cone silicon nanowire structure

Light trapping plays an important role in improving the conversion efficiency of thin-film solar cells. The good wideband light trapping is achieved using our periodically truncated cone Si nanowire （NW） structures, and their inherent mechanism is analyzed and simulated by FDTD solution software. Ordered cylinder Si NW structure with initial size orS0 nm and length of 200 nm is grown by pattern transfer and selective epitaxial growth. Truncated cone Si NW array is then obtained by thermal oxidation treatment. Its mean reflection in the range of 300-900 nm is lowered to be 5% using 140 nm long truncated cone Si NW structure, compared with that of 20% using cylinder counterparts. It indicates that periodically truncated Si cone structures trap the light efficiently to enhance the light harvesting in a wide spectral range and have the potential application in highly efficient NW solar cells.