ABSTRACT
Sb2 S3 is rapidly developed as light absorber material for solar cells due to its excellent photoelectric properties. However, the use of the organic hole transport layer of Spiro-OMeTAD and gold (Au) in Sb2 S3 solar cells imposes serious problems in stability and cost. In this work, low-cost molybdenum (Mo) prepared by magnetron sputtering is demonstrated to serve as a back electrode in superstrate structured Sb2 S3 solar cells for the first time. And a multifunctional layer of Se is inserted between Sb2 S3 /Mo interface by evaporation, which plays vital roles as: i) soft loading of high-energy Mo particles with the help of cottonlike-Se layer; ii) formation of surficial Sb2 Se3 on Sb2 S3 layer, and then reducing hole transportation barrier. To further alleviate the roll-over effect, a pre-selenide Mo target and consequentially form a MoSe2 is skillfully sputtered, which is expected to manipulate the band alignment and render an enhanced holes extraction. Impressively, the device with an optimized Mo electrode achieves an efficiency of 5.1%, which is one of the highest values among non-noble metal electrode based Sb2 S3 solar cells. This work sheds light on the potential development of low-cost metal electrodes for superstrate Sb2 S3 devices by carefully designing the back contact interface.
ABSTRACT
CsPbBr3 perovskite quantum dots (QDs) show great potential in various applications due to their size-dependent and excellent optoelectronic properties. However, it is still challenging to synthesize size-tunable CsPbBr3 QDs with purple emission. Herein, CsPbBr3 nanospheres (NS) with purple emission (432 nm) and wavelength-tunable photoluminescence were synthesized using a two-step recrystallization method for the first time. A nanocube (NC) strategy resulting from CsPbBr3 nanosphere self-assembly via polar solvent-induced surface ligand mismatch was proposed. The self-assembly process endows the QDs with wavelength-tunable photoluminescence ranging from 432 to 518 nm. The significant reduction in defects during self-assembly was confirmed by transient optical spectroscopy measurements, photoluminescence quantum yields (PLQY), and the disappearance of tail bands in the long-wavelength region of the photoluminescence (PL) spectrum. This theory demonstrated that the decrease in high defect surfaces and increase in specific surface area were the reasons for the decline in defects. Most importantly, these QDs could be used for the active jamming of optical imaging systems based on charged-coupled devices (CCDs), including laser imaging radar and low light level (LLL) night vision systems. QDs significantly increase the mean square error (MSE) of the image, while the detection rate of the target by the artificial intelligence algorithm decreased by 95.17%. The wide wavelength tunable emission caused by structural changes makes it arduous for silicon-based detectors to avoid the interference of QDs by adding filters or by other means.
ABSTRACT
Pollen is an important part of bioaerosols, and its complex refractive index is a crucial parameter for study on optical characteristics and detection, identification of bioaerosols. The reflection spectra of pear pollen within the 2. 5 - 15µm waveband were measured by squash method. Based on the measured data, the complex refractive index of pear pollen within the wave-band of 2. 5 to 15 µm was calculated by using Kramers-Kroning (K-K) relation, and calculation deviation about incident angle and different reflectivities at high and low frequencies.were analyzed. The results indicate that 18 degrees angle of incidence and different reflectivities at high and low frequencies have little effect on the results, and it is practicable to calculate the complex refractive index of pollen based on its reflection spectral data. The data of complex refractive index of pollen have some reference value for optical characteristics of pollen, detection and identification of bioaerosols.
Subject(s)
Pollen , Pyrus , Aerosols , RefractometryABSTRACT
A novel classification algorithm of hyperspectral imagery based on ant colony compositely optimizing support vector machine in spatial and spectral features was proposed. Two types of virtual ants searched for the bands combination with the maximum class separation distance and heterogeneous samples in spatial and spectral features alternately. The optimal characteristic bands were extracted, and bands redundancy of hyperspectral imagery decreased. The heterogeneous samples were eliminated form the training samples, and the distribution of samples was optimized in feature space. The hyperspectral imagery and training samples which had been optimized were used in classification algorithm of support vector machine, so that the class separation distance was extended and the accuracy of classification was improved. Experimental results demonstrate that the proposed algorithm, which acquires an overall accuracy 95.45% and Kappa coefficient 0.925 2, can obtain greater accuracy than traditional hyperspectral image classification algorithms.
Subject(s)
Algorithms , Artificial Intelligence , Image Enhancement/methods , Spectrum Analysis/methods , Support Vector MachineABSTRACT
Some kinds of phosphors were synthesized with Eu/Dy coating ZnO nanocrystals by co-precipitation approach derived from Zn(AC)2 2H2O, NaOH as precursors. The crystal structure and size were characterized by the X-ray diffraction Photoluminescence(PL) measurements show an intense red luminescence at 612 nm caused by transition of Eu3+ ions in ZnO:Eu3+ and intense luminescence band at 484 and 575 nm caused by transition of Dy3+ ions in ZnO:Dy3+. The results show that the energy transfer was realized from the host to the rare earth ions. The mechanism of the energy transfer was discussed. Meanwhile Eu/Dy co-coating nano ZnO can be achieved white light emission by energy transfer.
ABSTRACT
A density functional investigation of the interaction between calcium and magnesium univalent cations and RNA pyrimidine base (cytosine, thymine and uracil) was performed to determine geometric coordinates and free energies for all possible stable isomers at B3LYP/6-311 + G (2df, 2p) level. The most stable isomers C1M, T1M and U1M (M = Ca+ and Mg+) with the lowest free energy among the same pyrimidine base tautomers were calculated to determine the characters of infrared vibrations. According to the results, two characteristic infrared vibrations at wave numbers 1,684 and 1,765 cm(-1) were found for single pyrimidine base C1, at 1,747 and 1,792 cm(-1) for T1, 1,763 and at 1,796 cm(-1) for U1. In addition, spectrum shifts were found when the cations interact with the pyrimidine base tautomers. For deeper analysis, we found that when the stable complexes are formed, the cations are prone to act on the oxygen atoms, and cause the vibrational frequencies to change, the spectral lines belonging to the vibration of C--O--M turn out to redshift and the others turn out to blueshift. When the stable complex C1M is formed, the characteristic infrared vibration at 1,684 cm(-1) mainly caused by the ring's vibration turns out to blueshift about 10 cm(-1), and the another characteristic vibration of 1,765 cm(-1) caused by vibration of bond C--O with oxygen atom acting on cations directly turns out to redshift by 112 cm(-1) for complex C1Ca+ and by 110 cm(-1) for C1Mg+. When the stable complexes T1M are formed, the characteristic vibration of bond C--O--M turns out to redshift about 130 cm(-1) and the vibration of bond C--O turns out to blueshift about 55 cm(-1). When the stable complexes U1M are formed, the vibration of bond C--O--M turns out to redshift about 90 cm(-1) and about 50 cm(-1) for another C--O. The characteristic infrared vibration frequencies are changed obviously when tautomers act on the cations, which is mainly because cations take part in molecule's vibrations and change the force constants and reduced masses.
