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Using first principles calculations, we have confirmed the electronic and optical properties of 2D kagomes graphene doped with IVA elements (Si, Ge, Sn, Pb). The results show that Si-doped system has higher structural stability. The doping system increases the band gap of single-layer kagomes graphene, with Sn doping system being the most pronounced, and therefore can be considered as an attractive material for optoelectronic devices. The difference charge density and bonding population verify that the covalence of doping atoms and C atoms decreases, and that the degree of covalence diminution increases with increasing atomic number. The undoped kagomes graphene exhibits a strong light absorption capacity in the ultraviolet region, and the absorption peaks value decreases after doping, indicating that the element doping has a great weakening effect on the light absorption capacity, which has a certain potential significance for this material to be used as the antireflection film and wave permeable material of solar cells. In addition, the Pb and Sn-doped models possess the highest and lowest static dielectric constants, respectively. The peak value of electron energy loss is lower in the range of ultraviolet and visible wavelengths. These characteristics demonstrate that kagomes graphene offers substantial potential in the areas of optoelectronic and microelectronic devices. [ABSTRACT FROM AUTHOR]

In this paper, the adsorption behavior of Na atom on T-carbon (111) surface is investigated in detail by first principles calculations. The adsorption of Na atom on the T-carbon (111) surface is a chemical adsorption with excellent stability. The minor opening of the bandgap is present. The charges transfer from Na atom to C atom, which leads to a transition of the bonding properties from covalence to ionicity. For the H-site adsorption system, the adsorption energy is the lowest, indicating that the system is the most stable. At the same time, C-Na has the lowest bond population, indicating its strong ionic property. Additionally, the dielectric loss of the adsorbed system reduces, especially for the H-site adsorption, which is conducive to the improvement of the service life in electron material devices. In absorption spectrum, the peak values decrease and shift to the lower energy direction, resulting in the appearance of redshift phenomenon. The reflection peak and energy loss values are greatly reduced, in which the trend is most obvious for the H-site adsorption. The above analysis results provide a theoretical basis for the application of photosensitive devices and open a window on the design and control the micro-nano devices. [ABSTRACT FROM AUTHOR]

Exploring the next generation of invincible energy materials with fascinating properties is vital in the challenge of energy crisis. In this paper, we extract T-carbon as a potential candidate and have an insight into the electronic and optical properties by means of first principles. It is found that S1 position doping system is relatively more stable with the formation energy of 0.323 eV, and has the smallest bandgap value of 1.228 eV. Charge density difference maps show that the electron loss is obvious near the S atom and the covalent bond is weakened. The population analysis shows that the S atom will obtain electrons through competition, while the Se atom will lose electrons. Additionally, the peak values of 2 in the doped systems decrease significantly, especially for S2 doping system, indicating that S2 doping can effectively improve the service life in related devices. Compared with the instinct system, the absorption coefficient is lower in the UV region and greater in the visible region. The peak of energy loss spectrum reduces after doping, especially for Se1 doping. The results provide a theoretical basis for the industrial application of T-carbon in the energy microdevice fields. [ABSTRACT FROM AUTHOR]

In this paper, the microscopic electronic structure and related optical properties of the 4H-SiC (111) surface doped with B, Al, Ga elements are explored by first principles calculation methods. Compared with Al- and Ga-doped systems, the formation energy of B-doped system is found to be very small, showing excellent stability. The bandgaps of doped system decrease obviously, and an indirect bandgap is observed in all the systems. Charge density difference maps show that the covalency is increased after B doping and the iconicity is increased after Al and Ga doping. Moreover, due to the sharp increase in static dielectric constant and dielectric loss, the B-doped system can be used as the candidate for absorbing materials. In addition, the increase in the peak value of the absorption and reflectivity makes the doped systems more promising in the development of solar cells. [ABSTRACT FROM AUTHOR]

We use a first-principles calculation to explore the effects of vacancies on structural, electronic and optical properties of β - Si 3 N 4 based on density functional theory (DFT). The results show that after optimization, the Si vacancy system of β - Si 3 N 4 is more difficult to produce than N vacancy system under the same thermodynamic conditions. The band gaps including N vacancy and Si vacancy systems are smaller than that of the perfect crystal. The charge density difference and population analysis show that the bonding near Si vacancy has stronger covalent property, whereas those near nitrogen vacancy have stronger ionic property. For Si vacancy system, the materials have much higher values of the imaginary part of the dielectric constant than those of N vacancies and perfect β - Si 3 N 4 . The maximum value of the Si vacancy system in absorption and reflection spectra is lower than those in different nitrogen vacancy systems. [ABSTRACT FROM AUTHOR]

Structural stability along with the electronic and the optical properties of intrinsic 3C-SiC, Si 3 1 C 3 2 Na and Si 3 0 C 3 2 Na 2 are studied by the first-principles calculations. Si 3 1 C 3 2 Na system possesses the most considerate stability with lowest binding energy (E B) and formation energy (E f) compared to Si 3 0 C 3 2 Na 2 . It is observed that the non-filled impurity energy levels in the vicinity of the Fermi level can subsequently give rise to an enhancement of electrical conductivity of 3C-SiC. Through the analysis of charge difference density maps, it is found that covalence of bonds between the Na atom and nearby C atom reduces in varying degrees. In different concentrations of Na doping systems, especially for the supercell of Si 3 0 C 3 2 Na 2 , the real and imaginary parts of the dielectric constant are visibly added in the energy range of 0–0.5 eV, demonstrating that the dielectric loss property of the 3C-SiC is improved evidently. These features confirm that the Na-doped 3C-SiC semiconductor is propitious to the wide application of 3C-SiC in the field of absorbing materials. [ABSTRACT FROM AUTHOR]

Electronic structures and optical properties of IV A elements (Ge, Sn and Pb)-doped 3C-SiC are investigated by means of the first-principles calculation. The results reveal that the structure of Ge-doped system is more stable with a lower formation energy of 1.249 eV compared with those of Sn- and Pb-doped 3C-SiC systems of 3.360 eV and 5.476 eV, respectively. Doping of the IV A elements can increase the band gap, and there is an obvious transition from an indirect band gap to a direct band gap. Furthermore, charge difference density analysis proves that the covalent order of bonding between the doping atoms and the C atoms is Ge–C > Sn–C > Pb–C, which is fully verified by population values. Due to the lower static dielectric constant, the service life of 3C-SiC dramatically improved in production practice. Moreover, the lower reflectivity and absorption peak in the visible region, implying its wide application foreground in photoelectric devices. [ABSTRACT FROM AUTHOR]

Highlights • First principles is adopted to study the new properties of the counter electrodes. • The electronic structure of tin doped CuS are simulated by first princples. • The new optical properties of tin doped CuS are simulated by first princples. Abstract In order to study whether tin doped CuS could be used as counter electrodes for dye-sensitized solar cells, first-principles were used to calculate the electronic structure and optical properties of it. The calculated results show that tin ions can substitute two different kinds of copper ions in the supercell of CuS, and they demonstrate different properties. The calculated results of electronic structure indicate that the introduction of tin ions change the conductive properties of CuS counter electrode. The calculated results of optical properties indicate that the introduction of tin ions change the optical properties of CuS counter electrode, and tin doped CuS could be excellent counter electrodes for dye-sensitized solar cells. [ABSTRACT FROM AUTHOR]

Based on first‐principles with the generalized gradient approximation (GGA) of the Perdew–Burke–Ernzerhof (PBE) form, the authors carry out systematic investigations regarding the electronic structures and optical properties of zinc‐blende (ZB) ZnS doped with six types of transition metals. The Cd‐doped system has greater structural stability with a lower formation energy of 0.526 eV compared to other systems. Additionally, the band structures of systems are employed to show the superior semiconductor capacity of Mo‐ and Pt‐doped systems with decreased band gaps (EG) of 0.978 eV and 0.843 eV, which are smaller than those of the pure system and others. Moreover, charge difference density maps show that the covalent properties of MoS and PtS bonds are enhanced by exposing the electron‐deficient region. Meantime, optical properties, including absorption and reflectivity spectra, dielectric constant, and loss function, are introduced to reveal that the absorption spectra curves reach the lowest absorption peak of 2.375 × 105 cm−1 at 7.227 eV for the Mo‐doped system, in which the system exhibits a relatively negative reflectivity spectrum and dielectric loss that is expected in the solar cell industry, predicting its broad scope of application prospects in the photoelectric and microelectronic device fields. [ABSTRACT FROM AUTHOR]

We use first-principles calculations in this contribution to study electronic structures and optical properties, especially absorption and reflectivity spectra, dielectric constant and loss function of Li, Na, K, Be, Mg, Ca and Al adsorption behaviors on (2 0 0) surface of hexagonal silicon nitride (β-Si 3 N 4 ). The lower adsorption energy of −3.931 eV for Ca-adsorbed surface indicates that it has more excellent structural stability. The seven kinds of adsorptions are all featured by chemisorption with commonly negative value of adsorption energy, implying relatively abated capacity of defending the chemical corrosion formed by metals mentioned above. Band gaps of surfaces with different adsorptions are 0.113 eV, 0.099 eV, 0.113 eV, 0.147 eV, 0.154 eV, 0.151 eV and 0.111 eV for Li-, Na-, K-, Be-, Mg-, Ca- and Al-adsorbed surface structure, respectively, along with 0.143 eV for clean surface of β-Si 3 N 4 , which leads more efficient measures of potential for obtaining outstanding semiconductor properties for materials. Moreover, absorption spectra curve of surface drops to a lower peak value of 5.46 × 10 4  cm −1 , 4.94 × 10 4  cm −1 and 3.53 × 10 4  cm −1 for Na-, Mg- and Ca-adsorption, decreasing by 10.0%, 18.6% and 41.8% in contrast to clean surface, 6.07 × 10 4  cm −1 , respectively, in which the surface carries decreased reflectivity spectra and dielectric loss that are greatly valued and expected in solar cell industry, indicating its broader application potential in photoelectric and microelectronics devices fields. [ABSTRACT FROM AUTHOR]

Electronic structures and optical properties of zinc-blende aluminum nitride doped with transition metals are investigated. Lu-doped system possesses the most considerate stability with the lowest formation energy of −9.033 eV compared to others. Band structures of systems are introduced to investigate a more excellent semiconductor capacity for Re-doped system with a band gap (EG) of 0.689 eV, with others having band gaps of 2.120, 2.159, 1.806, 1.837 and 0.879 eV, respectively, much smaller than that of pristine one, 3.113 eV. Moreover, absorption spectra curve reaches the lowest peak of 2.558×105cm−1 for Os-doped system; simultaneously, the system exhibits a relatively negative reflectivity spectra and dielectric loss of 5.620 eV that are extensively expected in solar cell industry, predicting its broad scope of application prospects in photoelectric and microelectronic devices. [ABSTRACT FROM AUTHOR]

Using DFT-GGA-PW91 calculations we investigate the electronic structures and optical properties of doped GaP. It is found that the lattice constants and volume increase slightly for Al, In, As and Sb doped systems and E G distinctly decrease after doping. The formation energies are 0.587 and 0.273 eV for As and Sb doped systems, respectively, and lower remarkably than those in other systems, indicating that the stability of the two systems is higher. The direct band gap transition occurs when doped with In, As and Sb elements. The charge density difference images reveal that electron loss near Al atom is observed accompanying the enhancement of covalent bond feature, and then electron enrichment is present around N atom demonstrating that the ionic bond characteristic is obvious. The Sb-doped system has the higher static dielectric constant illustrating the applications in semiconductor devices. The absorption peak value is located at 194.7 nm for Al-doped system and this shows that the system can absorb a large amount of light and displays “Barrier-type” characteristics in UV region. In the visible region, the doped systems have lower reflectivity coefficient, indicating that the systems all have “clear-type” properties. This is conducive to fundamentally insights to a tunable band gap semiconductor with enormous potential in device fields. [ABSTRACT FROM AUTHOR]

Attractive potential applications of cubic boron nitride (c-BN) derive from the properties of semiconductors, widely used in optoelectronic and microelectronic devices. In this paper, the effects of element doping on the electronic structures and optical properties in cubic boron nitride are investigated. The Al- and Ga-doped systems have the lower bonding energies of −11.544 eV and −5.302 eV, respectively, indicating better stability. Difference charge density maps demonstrate that the electron loss increases after P doping and decreases after Al, Ga and As dopings, indicating that the covalent character of polar covalent bonds decreases by doping in the range of P, Al, Ga and As, which is in accordance with the calculated atom population values. The Al- and Ga-doped systems show lower dielectric loss, absorption and reflectivity in the lower energy region, displaying the 'transparent-type' characteristic and their potential applications in electron devices. [ABSTRACT FROM AUTHOR]

Highlights: [•] The stability of Mg-doped system is higher than that of Na-doped system. [•] A decline in bond strength of covalent bond after doping occurs. [•] The static dielectric constants at the zero frequency of the real part increase notably. [•] The host peaks in theoretical electron energy loss spectra are similar. [ABSTRACT FROM AUTHOR]

• The mh*/me* value of T-carbon is 0.107 indicating the better conductivity. • Doping improves the electron migration rate and conducive of T-carbon. • B doping causes the increasing of ionicity for the bonds 1 and 3. • The absorption and reflection values are reduced in the ultraviolet region for Al doping. The structure stability, electronic and optical properties of B and Al doped T-Carbon have been investigated by first-principles calculation under DFT framework. The calculated results show that the stability of B doping system is higher than that of the Al doping system and site 1 and 2 positions have equal contribution on the stability of systems. The mh*/me* value of T-carbon is 0.107 far away from 1, indicating that is conducive to the improvement of its conductivity. The doping of B and Al promotes the generation of impurity bands, and the disappearance of band gap, which is beneficial to the conductivity improvement of T-carbon. In Al doping systems, the absorption, reflection and loss peaks of light are reduced in the ultraviolet region, especially for the Al 2 system, which exhibits the application foundation and opens a window in the fields of photoelectron and microelectronics devices. [ABSTRACT FROM AUTHOR]

In this paper, first principles were adopted to calculate the electronic structure and optical properties of ZnO heavily doped by Sn for intermediate band materials, and we also investigated the effects of different Sn doping ratios on the intermediate band structure of ZnO. The results show that Sn heavily doped ZnO can form effective intermediate band, and it is caused by hybrids of Sn-s and O-p orbitals. When the Sn doping ratio reaches 1/8, an intermediate band structure with excellent optical properties can be formed. When Sn doping ratio reaches 1/4, ZnO shows electrical conductivity of alloy. • Sn heavily doped ZnO can form new intermediate band structure. • Sn heavily doped ZnO can form alloys when Sn doping ratio reaches 1/4. • The optical properties of ZnO heavily doped by Sn are predicted. [ABSTRACT FROM AUTHOR]

Electronic structure and optical properties of Cr-, Al- and Cr-Al co-doped 3C-SiC systems are investigated by the first principles method. The system presents the characteristics of n-type semiconductor materials A red-shift phenomenon after doping can be observed. The doped systems exhibit the "Transparent Type" characteristic in the visible region. Electronic structure and optical properties of Cr-, Al- and Cr-Al co-doped 3C-SiC systems are investigated by the first principles method. Al-, Cr- and Cr-Al co-doped systems present the characteristics of p-, n- and n-type semiconductor materials, respectively. Charge density difference results show that the covalency of bonding reduces after doping, which is verified by bond population values due to the fact that the values of single doped and Cr-Al co-doped systems are lower than that of un-doped 3C-SiC. The intrinsic 3C-SiC barely has microwave dielectric loss, however, it can be improved through Al or Cr doping, especially the effect of Al doping, indicating the enhanced ability of materials to absorb electromagnetic waves, which is helpful for SiC to be widely used in military and aerospace fields as absorbing materials. By analyzing the host peaks of the absorption coefficient and the loss function, it is found that there is a significant red shift after doping. SiC exhibits the "Transparent Type" characteristic based on the fact that it has a lower absorption coefficient and reflectance in the visible light region, which proves the foundation for optical property and opens a window for photoelectric devices. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • K 2 TiF 6 :Mn4+@CaF 2 phosphors were successfully prepared. • The luminous intensity of phosphors increased. • The moisture resistances of Mn4+-doped fluoride phosphors were enhanced. • K 2 TiF 6 :Mn4+@CaF 2 phosphors have a high stability. Abstract The moisture resistance and luminescent properties of K 2 TiF 6 :Mn4+ (KTF) phosphor was enhanced through a facile coating method to modify its surface, in which CaF 2 was used as a coating material. The structure, morphology, and composition of the KTF@CaF 2 samples were investigated via power X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), scanning electron microscopy (SEM), and transmission electron microscope (TEM). The luminescence properties were identified by luminescence spectra. The results show that, after being treated with CaF 2 , the surface morphology changed to some extent, and the luminous intensity of phosphor was enhanced. Through application of a moisture resistance test, the luminous intensity of KTF@CaF 2 phosphor was maintained, whereas the KTF was hydrolysed and the luminous intensity decreased. This was ascribed to local distortion of the crystalline field around Mn4+ in phosphors and the improvement of surface moisture resistance of phosphors after coating with CaF 2. [ABSTRACT FROM AUTHOR]

K 2 SiF 6 :Mn4+/g-C 3 N 4 (KSF/g-C 3 N 4) composite phosphors were directly synthesized by pretreatment of raw materials. This way avoided the damage to the luminescent properties of phosphors compared with the conventional method for preparing composites. The structure, morphology, and composition of K 2 SiF 6 :Mn4+/g-C 3 N 4 samples were investigated by X-ray Diffraction (XRD), Energy Dispersive Spectrometer (EDS) and Scanning Electron Microscope (SEM). Fluorescence and UV–Vis absorption spectra have also been measured to study their optical properties. By combine with g-C 3 N 4 , the absorption intensity of composite is greatly increased in the UV–Vis range, while its luminous intensity is also significantly enhanced. This is owing to g-C 3 N 4 increases the absorption capacity of the phosphor for UV–Vis light, and the overlap of the two emission spectra and excitation spectra promoted energy transfer to K 2 SiF 6 :Mn4+ phosphors. Image 1 1. Direct synthesis of phosphor composites by pretreatment of raw materials 2. K 2 SiF 6 :Mn4+/g-C 3 N 4 phosphors were successfully prepared. 3. The luminous intensity of phosphors increased significantly. [ABSTRACT FROM AUTHOR]