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Accelerating Pmn21-BAlNP properties prediction by machine learning based on first-principles calculation
摘要： In this paper, the CASTEP program and machine learning algorithm are used to study Pmn21-BxAl1-xNyP1-y. The mechanical stability, thermodynamic stability and molecular dynamics stability of several typical structures of Pmn21-BxAl1-xNyP1-y are estimated by CASTEP program. The results show that all the structures are stable. The data such as lattice constants and elastic properties of Pmn21-BxAl1-xNyP1-y are used as training sets of machine learning, then, the average absolute percent error (MAPE) of each model is calculated by using 7-fold cross-validation, and the lattice constant prediction model and shear modulus prediction model of Pmn21-BxAl1-xNyP1-y are selected respectively. Linear regression algorithm is used for modeling lattice constants, and Xgboost algorithm is used for modeling shear modulus. On the test sets, it is found that the error is within the acceptable range by comparing the data predicted by the models with the real data. Therefore, the machine learning prediction models of lattice constants, and shear modulus G have strong generalization ability. The electrical properties of Pmn21-BxAl1-xNyP1-y are calculated by using hybrid PBE0 functional. The direct band gaps are found in AlN, BP, AlP, B0.25Al0.75N, B0.75Al0.25P, B0.5Al0.5P, B0.25Al0.75P, AlN0.75P0.25, AlN0.5P0.5 and AlN0.25P0.75.
关键词： Pmn21-BxAl1-xNyP1-y,First-principles,Optoelectronic properties,Machine learning,Mechanical properties
更新于2025-09-10 09:29:36
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Regulating the Optoelectronic Properties of Nickel Dithiolene by the Substituents: A Theoretical Study
摘要： Dithiolene-based complexes show great potential to be applied as materials for organic optoelectronic devices. In this study, we theoretically designed a series of complexes based on nickel dithiolene and its substituted derivatives, the optoelectronic properties of which were comparatively studied by density functional theory (DFT)/time-dependent density functional theory (TD-DFT). The results show that the charge injection property of nickel dithiolene complexes can be significantly improved with introduction of electron-withdrawing groups. The charge transportation property of nickel dithiolene depends on the conjugation degree of the system. The energy gaps between highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) are determined by the substituents, which makes the maximum absorption wavelength red-shift from the visible to the near-infrared (NIR) region. The electron density difference graph shows that the electron transition from the ground state to the first excited state is assigned to π-π* transition mainly from HOMO to LUMO. The regularity of substituent effect revealed by us in this study will shed light on the application of nickel dithiolenes as potential optoelectronic materials.
关键词： substituents,DFT,nickel dithiolene,optoelectronic properties
更新于2025-09-10 09:29:36
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Shape-modulated multiple exciton generation and optoelectronic properties in PbSe nanostructures
摘要： Multiple exciton generation (MEG) in semiconductor nanostructures is of great interest for the enhancement of related performances in optoelectronic devices and for the shape dependence of conversion ef?ciency with which absorbed photons are converted into electron-hole pairs. However, theoretical insight into the coupling effects from the size and shape gradient on the MEG and related optoelectronic properties at the atomic level remains unclear. Here, we investigate the MEG and optoelectronic properties in PbSe nanostructures with different morphologies (nanocrystals, nanowires, and nanocones) based on the bond relaxation correlation mechanism, detailed balance principle, and Fermi statistical theory. It is found that size reduction of nanostructures can increase the bandgap, suppress the threshold energy, and enhance the MEG ef?ciency. Moreover, optimal conversion ef?ciency of PbSe nanostructures can be achieved by modulating the geometrical parameters.
关键词： bond relaxation correlation mechanism,PbSe nanostructures,Fermi statistical theory,Multiple exciton generation,optoelectronic properties
更新于2025-09-10 09:29:36
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Polyphosphazenes and Cyclotriphosphazenes with Propeller-like Tetraphenylethyleneoxy Side Groups: Tuning Mechanical and Optoelectronic Properties
摘要： A new class of polyphosphazene elastomers has been synthesized that combines a ?PN? backbone with both 2,2,2-trifluoroethoxy and tetraphenylethyleneoxy (TPEO) side groups. The polymer syntheses and photoproperties were first modeled using small molecule cyclic phosphazenes, and these were then applied to the high polymers. The TPEO groups confer useful mechanical and photophysical properties on the polymers. Thus, those polyphosphazenes with the more rigid bidentate TPEO side groups have higher fluorescence quantum yields than counterparts with monodentate TPEO groups. Different TPEO substituents also allow tuning of the side-group interactions to modify the elastomeric properties of the polymers. For example, the two-dimensional TPEO unit is a stronger physical cross-linker than the comparable cross-linkers used in earlier polyphosphazene elastomers. Thus, the elastomeric polymers containing the two-dimensional TPEO exhibit greatly improved mechanical properties compared to the previous ones. Moreover, hybrid materials that combine the new elastomers with single-walled carbon nanotubes (SWNTs) allow the fabrication of stretchable electronics with mechanically responsive properties.
关键词： mechanical properties,optoelectronic properties,stretchable electronics,tetraphenylethyleneoxy,polyphosphazene elastomers
更新于2025-09-09 09:28:46
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Effect of lack of oxygen on optical and electrical properties of RF magnetron sputtering deposited CuFeO2?x thin films
摘要： Delafossite CuFeO2?x thin ?lms were fabricated on quartz substrate using radio-frequency sputtering deposition under low O2 ?ow ratios from 9% to 0% at room temperature. The as-deposited ?lms were in amorphous phase and crystallized into rhombohedral 3R (R3m) delafossite structure after post annealing at 900?C for 2 h in ?owing N2 atmosphere. SEM images showed that the ?lms were composed of nano-sized crystallized grains, thin ?lm composed of smoother surface and higher oxygen content was obtained under higher oxygen percentage in sputtering gas. The optical transmission spectra of these ?lms were studied in the wavelength range 200–1500 nm and the results revealed a narrowing trend of direct bandgap from 3.09 eV to 2.98 eV with the decrease of oxygen ?ow ratio during deposition. All of the post-annealed CuFeO2?x thin ?lms exhibited p-type conductivity and linear ohmic contact feature with Cu electrodes. The carrier concentration of thin ?lms increased from 2.8 × 1017 cm?3 to 9.2 × 1019 cm?3 whereas the carrier mobility decreased from 9.74 cm2 ·V?1 ·s?1 to 0.035 cm2 ·V?1 ·s?1 as the oxygen ?ow ratio reduced from 9% to 0%. The ability of controlling compound com- position enables tuning of carrier concentration and mobility in CuFeO2?x and o?ering essential technical basis in engineering photoelectronic devices.
关键词： CuFeO2?x,p-type conductivity,optoelectronic properties
更新于2025-09-09 09:28:46
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Effects of Al2O3 buffer layer and annealing on the structural and optoelectronic properties of AZO films
摘要： Transparent conductive aluminum-doped ZnO (AZO) films are deposited on glass substrates using radio frequency (rf) magnetron sputtering, with an AZO ceramic target (Al2O3 content is ~ 3 wt%). Before the AZO films is coated, the hydrophilicity of the surface of the glass substrate is increased by oxygen plasma etching. The grey Taguchi method is used to determine the effect of the deposition parameters on the structural and optoelectronic properties of AZO films. In the confirmation runs, using the grey Taguchi method, an improvement of 46.3% in electrical resistivity and of 1.74% in transmittance is observed. The effect of an Al2O3 buffer layer is also determined. When the thickness of the Al2O3 buffer is increased (from 50 nm to 150 nm), the intensity of the (0 0 2) peak for the AZO films increases and the peaks become sharper, the resistivity of the AZO films is decreased and the transmittance is slightly reduced. Annealing at 500 °C in a vacuum (2.0 Pa) for a period of 30 min, increases the performance of the AZO/Al2O3/glass to better than that for AZO/glass samples. Using a Rockwell-C hardness tester, the AZO/Al2O3 (50 nm)/glass film are classified as HF1, which represents good adhesive mechanical strength. The crystallinity of AZO/Al2O3 (50 nm)/glass samples that are annealed at 500 °C for 30 min is improved, the electrical resistivity is 9.70 × 10?4 ? cm and the optical transmittance in the visible region is approximately 85%. The figure of merit shows that the bi-layer films have better optoelectronic performance.
关键词： optoelectronic properties,AZO films,Al2O3 buffer layer,structural properties,annealing
更新于2025-09-04 15:30:14
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Structural and Optical Properties of Cs2AgBiBr6 Double Perovskite.
摘要： We present a comprehensive study of the relationship between the crystal structure and optoelectronic properties of the double perovskite Cs2AgBiBr6, which has emerged as a promising candidate for photovoltaic. Based on single-crystal/powder X-ray diffraction and neutron powder diffraction, we have revealed the presence of a structural phase transition at Ts ～122K between the room-temperature cubic structure (space group F mˉ3m) and a new low-temperature tetragonal structure (I4/m). From reflectivity measurements we found that the peak exciton energy Eex ≈ 2.85 eV near the direct gap shifts proportionally to the tetragonal strain, which is consistent with the Eex being primarily controlled by a rotational degree of freedom of the crystal structure, thus by the angle Bi-Br-Ag. We observed the time-resolved photoluminescence kinetics and we found that, among the relaxation channels, a fast one is mainly present in the tetragonal phase, suggesting that its origin may lie in the formation of tetragonal twin domains.
关键词： optoelectronic properties,structural phase transition,double perovskite,photovoltaic,Cs2AgBiBr6
更新于2025-09-04 15:30:14