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Narrow-band-gap III-V semiconductor nanowires (NWs) with a suitable band structure and strong light-trapping ability are ideal for high-efficiency low-cost solar water-splitting systems. However, due to their nanoscale dimension, they suffer more severe corrosion by the electrolyte solution than the thin-film counterparts. Thus, short-term durability is the major obstacle for using these NWs for practical water-splitting applications. Here, we demonstrated for the first time that a thin layer (∼7 nm thick) of compact TiO2 deposited by atomic layer deposition can provide robust protection to III-V NWs. The protected GaAs NWs maintain 91.4% of its photoluminescence intensity after 14 months of storage in ambient atmosphere, which suggests the TiO2 layer is pinhole-free. Working as a photocathode for water splitting, they exhibited a 45% larger photocurrent density compared with unprotected counterparts and a high Faraday efficiency of 91% and can also maintain a record-long highly stable performance among narrow-band-gap III-V NW photoelectrodes; after 67 h photoelectrochemical stability test reaction in a strong acid electrolyte solution (pH = 1), they show no apparent indication of corrosion, which is in stark contrast to the unprotected NWs that fully failed after 35 h. These findings provide an effective way to enhance both stability and performance of III-V NW-based photoelectrodes, which are highly important for practical applications in solar-energy-based water-splitting systems.

Inverted perovskite solar cells (p-i-n PSCs) have been fascinated due to rapid progress of performance in recent years. PEDOT:PSS is commonly used hole transport material (HTM) in p-i-n PSCs having hygroscopic and acidic nature that leads towards poor performance of device. Therefore, it is necessary to replace PEDOT:PSS with stable HTM. In this paper, theoretical study is carried out to investigate physical parameters that can affect the performance of p-i-n PSCs with copper iodide (CuI) as HTM. These parameters include the effect of doping density of electron transport material (ETM), absorber and HTM as well as defect density and thickness of absorber on the performance of p-i-n PSCs. Hole mobility and thickness of HTM are also investigated. It is found that performance of p-i-n PSCs is strongly dependent on defect density and thickness of absorber. Upon final optimization, device attains PCE of more than 21% which is encouraging.

Traditional seawater-source heat pump (SWHP) needs to set water intake and titanium plate heat exchanger which result in high initial investment and large work quantity. A new type of SWHP was recommended, which use capillaries made by PPR (polypropylene random) submerged in seawater as the front-end heat exchanger. Glycol antifreeze solution was injected into the capillaries used as circulating medium. Capillaries were used as heat exchanger between seawater outside and glycol antifreeze solution inside. This method can greatly reduce the initial investment and improve COP of the SWHP system. This paper discusses the feasibility of capillaries used as the front-end heat exchanger of SWHP. An experimental platform was designed and constructed to measure the heat transfer coefficient of capillaries, and collect the operating data to calculate COP of SWHP in winter and summer. The experiment results show that, the average COP of the SWHP system is 3.17 in winter and 3.3 in summer. When the velocity of glycol in capillary tube is 0.15 m/s, the measured value of capillary heat transfer coefficient k is 161.01 W/(m2·°C). The efficiency of capillary heat exchanger was greater than 96.4%, which shows that it is feasible to use capillaries as the front-end heat exchanger of SWHP.

To realize the bidirectional cognitive computing supported by cloud technology, the cloud model is taken as a bidirectional cognitive computing model based on probability and statistics, a bidirectional cognitive calculation method is constructed, and the bidirectional cognitive conversion between concept connotation and extension is studied. In view of the defects in the existing backward cloud conversion algorithm, two stable multistep backward cloud conversion algorithms are proposed, which lays the foundation for the realization of a stable bidirectional cognitive calculation process. A bidirectional cognitive computing model is proposed, which combines the characteristics of human cognition and the bidirectional cognitive conversion algorithm to simulate bidirectional cognitive computing process based on concept by means of calculation. Moreover, the application of bidirectional cognitive transform algorithm in image segmentation is studied combined with the characteristics of human image cognition. It is also compared with the classical algorithm and methods based on cloud model. The results show that the proposed method has lower mean error and is obviously better than other algorithms, which fully proves the effectiveness of the method.

We propose a tunable repetition rate multiplier for optical phase code sequences consisting of a temporal grating and a temporal 4-F system. The temporal 4-F imaging preserves the input code words at the output, while the temporal grating multiplies the code rate by an integer being programed via an arbitrary wave generator. A lower bound and an upper bound are, respectively, set for aperture width of involved active elements and dispersion deviation of involved dispersion elements to control output phase distortion. By numerical simulation, an 8-period-long input sequence of individual phase Barker code with 10 ns code chip width and 2-rad peak phase is multiplied from 4 to 16 MHz corresponding to multiplication factor tuned from one to four. The expected phase preserving feature and tunable capacity are validated. Degradations including leaked ripples and envelop fluctuation are successfully controlled by the aperture-width bound and the dispersion-deviation bound, respectively. The proposed multiplier provides a promising potential for multifunctional photonic-aided continuous-wave radars with enhanced agility and adaptability.

Kesterite Cu2ZnSnS4 (CZTS) has attracted attention as an earth-abundant alternative to commercially successful CIGS solar cells. CZTS exhibits decent optoelectrical properties while having excellent stability on top of being an earth-abundant, low-cost and non-toxic material. Therefore, in recent years, there has been a significant research effort to develop CZTS-based devices. The efficiency of CZTS solar cells reached 12.6% in 2013, and this was a remarkable achievement at the time. However, the efficiency of these devices has been stagnant since then while emerging technologies, most notably perovskite solar cells, keep breaking record after record. Currently, CZTS research focuses on discovering the secrets of material properties that hinder the efficiency of CZTS solar cells while branching out to develop alternative applications for this material. In this review, we summarize the interesting properties of CZTS as well as its promising applications, which include thin-film solar cells, charge-transfer layers in perovskite solar cells, and photoelectrochemical water splitting while briefly commenting on its other possible applications.

With the advent of the era of big data, the deep integration of the Internet and healthcare makes medical data exponential growth. How to ensure data security is particularly important. However, the traditional encryption speed is no longer applicable to massive information processing. Based on Hadoop open source project, this paper designs and studies distributed RSA encryption algorithm based on distributed file system and programming model. In the beginning of this paper, a design scheme of distributed encryption algorithm based on platform is proposed, the distribution of distributed algorithm is determined, module partition and process control are carried out to the whole, and the distributed encryption function of the single computer encryption system is realized. Finally, through the large-scale distributed cluster built in the laboratory, the distributed encryption algorithm is tested by function test, extensibility test and efficiency test. It is proved that the distributed encryption algorithm can optimize the operation speed and can be applied to the processing of massive data.

With the rapid development of information technology, especially network technology, people’s ability to collect, store and transmit data are increasing. The data have exploded in an explosive manner. In sharp contrast, the ability to make valuable data for decision making is very poor. In this paper, data mining is the most basic problem. In order to overcome the shortcomings of the traditional clustering algorithm for k-means clustering, it is difficult to determine the initial clustering center and the k-means algorithm is improved. When determining the initial K-, the convergence factor is improved and the global optimum is achieved, so as to realize the determination of clustering center. By using improved k-means algorithm to approximate the criminal data, the validity of this method is verified.

We propose a feasible temporal filtering (or spectrum weighting) system to implement optical differentiation with arbitrarily-tunable order. Differentiation order is tuned by programming the temporal weighting mask (TWM) as power function of different exponents, not limited by the structure of the system. Assembly of the system is feasible, since the active parts are implemented by electro-optic elements and some key elements are reused between sub-systems involved in the scheme. Tuning of the system is simple, since electronically pre-stored TWMs are easy to switch among each other. The order-tunable functionality is verified by numerically testing the differentiation cases of normalized input pulse duration ranging from 0.1 to 0.4, and of differentiation order tuned from 1 to 10. Good accuracy is achieved, and measured by root mean square error lower than 0.1. Feasibilities of the system are also verified in terms of accuracy maintaining and distortion avoiding. Compared with existing methods, apart from the arbitrary order-tunable capacity and good accuracy, our proposed optical differentiator also possesses properties of good compactness and constant complexity. The proposed differentiator has unique applications on multi-peak waveform generation for optical communications and photonics-aided Radars with enhanced agility and feasibility.

Digital PCR generally includes two parts. That is, the PCR amplification and fluorescence signal analysis. In the PCR amplification stage. Using digital PCR to dilute samples onto a single molecule level, the average to dozens to tens of thousands of units in chemical reaction, make each reaction unit of target molecules is 0 or 1, makes the target molecules positive signal detection. One of them will use the upper software control laboratory PCR instrument operation, instrument of the data acquisition, as well as to the scientific analysis and processing the data collected, is advantageous for the quantitative analysis of the gene and detection. The software to control one PCR instrument operation and work. In addition this instrument will collect data uploaded to PC through USB interface, through analysis and deal with the PC software. Finally experimental conclusions.

In this paper, we evaluate the developer’s efficiency by an improved DEA model. It is a combination of traditional C2R model and fuzzy mathematics, which forms a new fuzzy DEA model. The model overcomes the strong objective factors that in the traditional DEA model and not support fuzzy input and output. It is conducive to improve the efficiency of the developer, which is very important for decision of makers.

133 camelina samples were used to build the Fourier transform infrared (FT-IR) prediction model. Several methods have been used for the establishment of the predicting model, but support vector machine was rarely used in FT-IR area to build the prediction model. The aim of this study was to develop a new model for predicting protein with higher accuracy. In the spectra region 690–1700 cm$$^{-1}$$, the SVM method was better than that of PLS and PCR. In the development of SVM, the $$\hbox {R}_{\mathrm{RMSEC}}^{2}$$ and $$\hbox {R}_{\mathrm{RMSEP}}^{2}$$ of the model were 0.83963 and 0.96578 respectively, and the RPD was 5.5016. The RPD was greater than that of PLS and PCR. The FT-IR was effective in predicting the content of camelina protein and SVM was a better method to build prediction model.

Objective: an innovative concept and method is introduced to use a 3-D anatomical graphic pattern called visual patient (VP) visually to index, represent, and render the medical diagnostic records (MDRs) of a patient, so that a doctor can quickly learn the current and historical medical status of the patient by manipulating VP. The MDRs can be imaging diagnostic reports and DICOM images, laboratory reports and clinical summaries which can have clinical information relating to medical status of human organs or body parts. Methods: the concept and method included three steps. First, a VP data model called visual index object (VIO) and a VP graphic model called visual anatomic object (VAO) were introduced. Second, a series of processing methods of parsing and extracting key information from MDRs were used to fill the attributes of the VIO model of a patient. Third, a VP system (VPS) was designed to map VIO to VAO, to create a VP instance for each patient. Results: a prototype VPS has been implemented in a simulated hospital PACS/RIS integrated environment. Two evaluation results showed that more than 70% participating radiologists would like to use the VPS in their radiological imaging tasks, and the efficiency of using VPS to review the tested patients’ MDRs was 2.24 times higher than that of using PACS/RIS, while the average accuracy Pac > by using PACS/RIS was better than that by using VPS; however, this difference was only about 4%. Conclusion: the developed VPS can show the medical status of patient organs/sub-organs with 3-D anatomical graphic pattern and will be welcomed by radiologists with better efficiency in reviewing the patients’ MDRs and with acceptable accuracy. Significance: the VP introduces a new way for medical professionals to access and interact with a huge amount of patient records with better efficiency in the big data era.

This study demonstrates a facile and general one-pot synthetic approach for all-inorganic colloidal cesium lead halide (CsPbX3, X = Cl, Br, I, mixed Cl/Br, Br/I) perovskite nanocrystals (NCs) by directly heating the precursors/solvent/ligands. In contrast to typical routes, these reactions are conducted in open air, requiring neither high temperature dissolution nor a vacuum/inert atmosphere. The composition, shape and size of the as-synthesized NCs can be finely tuned by varying the reaction parameters such as temperature and time, ligand species and precursor halide ratios. CsPbX3 morphologies may be varied from perovskite nanoplatelets (NPLs) to nanosheets and sphere-like NCs, each with tunable absorption spectra and photoluminescence (PL) emissions. In particular, mixed halide NCs with controllable band gaps and PL emission across the entire visible region have been demonstrated by tuning the precursor halide ratios. The reproducibility and scalability of the present synthetic protocol is elaborated by upscaling the amounts of chemicals and solvents/ligands in a representative synthesis of CsPbBr3 NPLs. The representative large-scale CsPbBr3 NPLs exhibit a high PL quantum yield of 73.56%.

We report the gram-scale synthesis of Cu-poor CZTS nanocrystals (NCs) with tuned shapes and compositions by using a facile phosphine-free heat-up procedure. Based on the detailed characterization and analyses of the evolution of crystal phases, compositions, morphologies and optical spectra over the reaction stage and temperature, we explore the reaction mechanism. The synthesis reaction involves the formation of binary CuS (covellite) nanoparticles at room temperature, and the conversion from the as-formed CuS to Zn–Sn-codoped CuS NCs as intermediates at 150 °C and finally to quaternary CZTS NCs in the kesterite phase at 220 °C, during which the NCs gradually grow due to the progressive incorporation of foreign cations (Zn2+ and Sn2+) into the as-formed CuS NCs. The introduction of dodecanethiol (DT) leads to the formation of bullet-like CZTS NCs in the wurtzite phase. The Cu-poor CZTS synthesis is reproducible by upscaling the amounts of chemicals and solvents/ligands, which allows for a promising approach to gram-scale production of Cu-based chalcogenides for potential applications in photovoltaics.

The materials used in detection of high energy photons are of primary importance in the construction of efficient, cost effective and sensitive detectors. Current research into Perovskites for solar cell technology has stimulated interest in their potential alternative uses, one of which is in direct photon conversion radiation detectors, owed primarily to their high-Z elemental composition twinned with exceptional charge carrier transport properties. Here, the Perovskite CsPbBr 3 has been synthesised through solution growth. The raw CsPbBr 3 was a granular powder which was formed into disks of 8 mm diameter and 1-2 mm thickness by two methods: 1). the powders were pressed into pellets using a hydraulic press or 2). sealed in a quartz ampoule under vacuum and then melted and quenched to form a polycrystalline solid which was cut to size. Metallic contacts were deposited on the front and back faces to permit charge collection. The results from the pressed devices are promising, particularly given that the production method is cost effective, repeatable and scalable. The solid-from-melt devices show similar performance but further development is required to optimise the production method.

Perovskite solar cells (PSCs) have achieved tremendous success within just a decade. This success is critically dependent upon compositional engineering, morphology control of perovskite layer, or contingent upon high-temperature annealed mesoporous TiO2, but quantitative analysis of the role of facile TiCl4 treatment and thickness control of the compact TiO2 layer has not been satisfactorily undertaken. Herein, we report the facile thickness control and post-treatment of the electron transport TiO2 layer to produce highly efficient planar PSCs. TiCl4 treatment of TiO2 layer could remove the surface trap and decrease the charge recombination in the prepared solar cells. Introduction of ethanol into the TiCl4 aqueous solution led to further improved open-circuit voltage and short-circuit current density of the related devices, thus giving rise to enhanced power conversion efficiency (PCE). After the optimal TiCl4 treatment, PCE of 16.42% was achieved for PSCs with TiCl4 aqueous solution-treated TiO2 and 19.24% for PSCs with TiCl4 aqueous/ethanol solution-treated TiO2, respectively. This work sheds light on the promising potential of simple planar PSCs without complicated compositional engineering and avoiding the deposition and optimization of the mesoporous scaffold layer.

In this paper, a method to optimize the sensitivity of multi-core fiber (MCF) strain sensors by properly designing fiber structure is investigated from theory, simulation and experiments. The mode-coupling between cores is tuned by changing fiber structure parameters, which will result in a change in sensitivity of such MCF strain sensor. Thus it is possible to obtain an optimal sensitivity in advance by reasonably designing the fiber structure parameters. Taking a symmetrical four-core fiber as an example, numerical simulation has been implemented and the results show that the highest strain sensitivity of −11.85 nm/me can be obtained when the core diameter, the core-to-core pitch, the refractive index difference between core and cladding are set to 4.53 µm, 18.1 µm and 0.0108, respectively. The method was verified through experiments and the experimental results are very close to the simulated results. The proposed MCF strain sensor has the advantages of simple structure, low cost and high sensitivity, which makes it have high research value in commercial sensing applications.

With record cell efficiency of 21.7%, CIGS solar cells have demonstrated to be a very promising photovoltaic (PV) technology. However, their market penetration has been limited due to the inherent high cost of the cells. In this work, to lower the cost of CIGS solar cells, all nonvacuum-processed CIGS solar cells were designed and developed. CIGS absorber was prepared by the annealing of electrodeposited metallic layers in a chalcogen atmosphere. Nonvacuum-deposited Ag nanowires (NWs)/AZO transparent electrodes (TEs) with good transmittance (92.0% at 550 nm) and high conductivity (sheet resistance of 20 Ω/□) were used to replace the vacuum-sputtered window layer. Additional thermal treatment after device preparation was conducted at 220 °C for a few of minutes to improve both the value and the uniformity of the efficiency of CIGS pixel cell on 5 × 5 cm substrate. The best performance of the all-nonvacuum-fabricated CIGS solar cells showed an efficiency of 14.05% with Jsc of 34.82 mA/cm(2), Voc of 0.58 V, and FF of 69.60%, respectively, which is comparable with the efficiency of 14.45% of a reference cell using a sputtered window layer.

In coherent digital holographic microscopy, speckle noise is incorporated into the hologram so that phase reconstruction may become worse in quality. Meanwhile, the previous speckle suppression algorithms are not satisfactory to solving this problem due to under- or over-filtering the image with a purely multiplicative or additive phase processing technique. In this paper, the complex-valued speckle effect on the phase reconstruction is first disclosed in theory by creating a multiplicative complex-valued model. A composite noise processing approach is subsequently proposed, which combines a revision of speckle reducing anisotropic diffusion algorithm and an improvement of dual-domain noise processing technique by developing a principal component analysis model for the image blocks to determine the true noise standard deviation in the algorithm for optimization of speckle suppression. The phase unwrapping algorithm with proposed speckle suppression processing is optimally combined to obtain better robustness and phase reconstruction quality of the image. The results are satisfactory. It verifies the validity of the proposed method especially for the objects with continuously-varied phases

Flexible devices are garnering substantial interest owing to their potential for wearable and portable applications. Here, flexible and self-powered photodetector arrays based on all-inorganic perovskite quantum dots (QDs) are reported. CsBr/KBr-mediated CsPbBr3 QDs possess improved surface morphology and crystallinity with reduced defect densities, in comparison with the pristine ones. Systematic material characterizations reveal enhanced carrier transport, photoluminescence efficiency, and carrier lifetime of the CsBr/KBr-mediated CsPbBr3 QDs. Flexible photodetector arrays fabricated with an optimum CsBr/KBr treatment demonstrate a high open-circuit voltage of 1.3 V, responsivity of 10.1 A W-1 , specific detectivity of 9.35 × 1013 Jones, and on/off ratio up to ≈104 . Particularly, such performance is achieved under the self-powered operation mode. Furthermore, outstanding flexibility and electrical stability with negligible degradation after 1600 bending cycles (up to 60°) are demonstrated. More importantly, the flexible detector arrays exhibit uniform photoresponse distribution, which is of much significance for practical imaging systems, and thus promotes the practical deployment of perovskite products.

Chalcopyrite Cu(In,Ga)(S,Se)2 (CIGSSe) thin films have been deposited by a novel, nonvacuum, and cost-effective electrostatic spray-assisted vapor deposition (ESAVD) method. The generation of a fine aerosol of precursor solution, and their controlled deposition onto a molybdenum substrate, results in adherent, dense, and uniform Cu(In,Ga)S2 (CIGS) films. This is an essential tool to keep the interfacial area of thin film solar cells to a minimum value for efficient charge separation as it helps to achieve the desired surface smoothness uniformity for subsequent cadmium sulfide and window layer deposition. This nonvacuum aerosol based approach for making the CIGSSe film uses environmentally benign precursor solution, and it is cheaper for producing solar cells than that of the vacuum-based thin film solar technology. An optimized CIGSSe thin film solar cell with a device configuration of molybdenum-coated soda-lime glass substrate/CIGSSe/CdS/i-ZnO/AZO shows the photovoltaic (j-V) characteristics of Voc=0.518 V, jsc=28.79 mA cm(-2), fill factor=64.02%, and a promising power conversion efficiency of η=9.55% under simulated AM 1.5 100 mW cm(-2) illuminations, without the use of an antireflection layer. This demonstrates the potential of ESAVD deposition as a promising alternative approach for making thin film CIGSSe solar cells at a lower cost.

In our work, eco-friendly, non-vacuum and low cost Electrostatic Spray Assisted Vapour Deposition (ESAVD) method has been used to produce Cu(In,Ga)(S,Se)2 (CIGS) solar cells. Copper (Cu) deficient (Cu/In + Ga = 0.76) CIGS films were designed to avoid the rather dangerous KCN treatment step for the removal of conductive minor phases of Cu2S/Cu2Se. A simple sodium (Na) treatment method was used to modify the morphology and electronic properties of the absorber and it clearly improved the solar cell performance. The SEM and XRD results testified a slightly increase of the grain size and (112) crystal orientation in the Na-incorporated CIGS thin films. From the Mott-schottky results, it can be seen that the functions of the Na treatment in our non-vacuum deposited CIGS are mainly used for defect passivation and reduction of charge recombination. Photovoltaic characteristics and j-V curve demonstrated that the dipping of CIGS films in 0.2 M NaCl solution for 20 minutes followed by selenization at 550 °C under selenium vapor resulted in the optimum photovoltaic performance, with jsc, Voc, FF and η of the optimized solar cell of 29.30 mA cm−2, 0.564 V, 65.59% and 10.83%, respectively.

In this article, an environmentally friendly and non vacuum electrostatic spray assisted vapour deposition (ESAVD) process has been developed as an alternative and low cost method to deposit CIGS absorber layers. ESAVD is a non-vacuum chemical vapour deposition based process whereby a mixture of chemical precursors is atomized to form aerosol. The aerosol is charged and directed towards a heated substrate where it would undergo decomposition and chemical reaction to deposit a stable solid film onto the substrate. A sol containing copper, indium and gallium salts, as well as thiourea was formulated into a homogene-ous chemical precursor mixture for the deposition of CIGS films. After selenization, both XRD and Raman results show the presence of the characteristic peaks of CIGSSe in the fabricated thin films. From SEM images and XRF results, it can be seen that the deposited absorbers are promising for good performance solar cells. The fabricated solar cell with a typical structure of glass/Mo/CIGSSe/CdS/i-ZnO/ITO shows efficiency of 2.82% under 100mW/cm2 AM1.5 illumination.

Hole transport material (HTM) plays an important role in the efficiency and stability of perovskite solar cells (PSCs). Spiro-MeOTAD, the commonly used HTM, is costly and can be easily degraded by heat and moisture, thus offering hindrance to commercialize PSCs. There is dire need to find an alternate inorganic and stable HTM to exploit PSCs with their maximum capability. In this paper, a comprehensive device simulation is used to study various possible parameters that can influence the performance of perovskite solar cell with CuI as HTM. These include the effect of doping density, defect density and thickness of absorber layer, along with the influence of diffusion length of carriers as well as electron affinity of electron transport layer (ETM) and HTM on the performance of PSCs. In addition, hole mobility and doping density of HTM is also investigated. CuI is a p-type inorganic material with low cost and relatively high stability. It is found that concentration of dopant in absorber layer and HTM, the electron affinity of HTM and ETM affect the performance of solar cell minutely, while cell performance improves greatly with the reduction of defect density. Upon optimization of parameters, power conversion efficiency for this device is found to be 21.32%. The result shows that lead-based PSC with CuI as HTM is an efficient system. Enhancing the stability and reduction of defect density are critical factors for future research. These factors can be improved by better fabrication process and proper encapsulation of solar cell.

In this Letter, the loss and gain characteristics of an unconventional InxGa1−xAs/GaAs asymmetrical step well structure consisting of variable indium contents of InxGa1−xAs materials are measured and analyzed for the first time, to the best of our knowledge. This special well structure is formed based on the indium-rich effect from the material growth process. The loss and gain are obtained by optical pumping and photoluminescence (PL) spectrum measurement at dual facets of an edge-emitting device. Unlike conventional quasi-rectangle wells, the asymmetrical step well may lead to a hybrid strain configuration containing both compressive and tensile strains and, thus, special loss and gain characteristics. The results will be very helpful in the development of multiple wavelength InGaAs-based semiconductor lasers.

In this paper, an experimental approach to acquiring true spontaneous emission rate of optically-pumped InGaAs/GaAs quantum-well laser structure is described. This method is based on a single edge-emitting laser chip with simple sample processing. The photoluminescence spectra are measured at both facets of the edge-emitting device and transformed to the spontaneous emission rate following the theory described here. The unusual double peaks appearing in the spontaneous emission rate spectra are observed for the InGaAs/GaAs quantum-well structure. The result is analyzed in terms of Indium-rich island and Model-Solid theories. The proposed method is suitable for electrically-pumped quantum-well laser structures, as well.

In this paper, an absolute-phase unwrapping and speckle suppression approach to reconstruct a three-dimensional (3-D) image of an object with laser digital holography is described. This method offers three advantages to enhance the performance of the phase reconstruction technique. First, both speckle suppression and phase unwrapping are processed in the complex amplitude domain rather than in the single phase or amplitude domain. With this approach, the phase details of the object are better preserved upon phase reconstruction. Second, the proposed algorithm requires no threshold determination and thus achieves self-adaptive speckle suppression and robust phase unwrapping, in contrast to other methods. Finally, an improved dual-domain image denoising method is applied to further remove speckle-remnant-induced phase distortion. Ideal 3-D phase reconstruction results are obtained both theoretically and experimentally for the first time.

In this study, we report bulk heterojunction solar cells using hybrid heterojunction nanorods as photoactive material. The core–shell nanorods are obtained via self-assembly of low band gap p-type oligomers onto ZnO nanorod surfaces. This produces highly soluble donor–acceptor nanostructures that feature a grafted p-type semiconducting monolayer with a band gap of 2.1 eV. The solution processing of the coaxial nanorods into thin films leads to bulk heterojunctions of particularly large donor–acceptor interfaces. Importantly by simple processing donor domains smaller than typical exciton diffusion length of organic semiconductors are obtained which guaranties efficient exciton dissociation. The corresponding solar cells reveal that the hydrid nanorod layers form efficient interpenetrated networks which lead to external quantum efficiency of 20% at the absorption maximum λmax = 498 nm. Although the donor domains of these hybrid bulk heterojunction are constituted by monolayers, transient absorption spectros...