采用第一性原理贋势平面波方法对（110）应变下立方相Ca_2P_（0.25）Si_（0.75）的能带结构及光学性质进行模拟计算,全面分析了应变对Ca_2P_（0.25）Si_（0.75）能带结构、光学性质的影响.计算结果表明：在92%～100%压应变范围内随着应...采用第一性原理贋势平面波方法对（110）应变下立方相Ca_2P_（0.25）Si_（0.75）的能带结构及光学性质进行模拟计算,全面分析了应变对Ca_2P_（0.25）Si_（0.75）能带结构、光学性质的影响.计算结果表明：在92%～100%压应变范围内随着应变的逐渐增大导带向低能方向移动,价带向高能方向移动,带隙呈线性逐渐减小,但始终为直接带隙;在100%～102%张应变范围内随着应变的增加,带隙呈逐渐增大,应变达到102%直接带隙最大Eg=0.54378 e V;在102%～104%应变范围内随着应变的增加,带隙逐渐减小;当应变大于104%带隙变为间接带隙且带隙随着应变增大而减小.施加应变Ca_2P_（0.25）Si_（0.75）的介电常数、折射率均增大;施加压应变吸收系数增加,反射率减小;施加张应变吸收系数减小,反射率增加.综上所述,应变可以改变Ca_2P_（0.25）Si_（0.75）的电子结构和光学常数,是调节Ca_2P_（0.25）Si_（0.75）光电传输性能的有效手段.展开更多
The electronic structure of YbB6 crystal was studied by means of density functional （GGA ＋ U） method. The calculations were performed by FLAPW method. The high accurate band structure was achieved. The correlation ...The electronic structure of YbB6 crystal was studied by means of density functional （GGA ＋ U） method. The calculations were performed by FLAPW method. The high accurate band structure was achieved. The correlation between the feature of the band structure and the Yb-B6 bonding in YbB6 was analyzed. On this basis, some optical constants of YbB6 such as reflectivity, dielectric function, optical conductivity, and energy-loss function were calculated. The results are in good agreement with the experiments. The real part of the optical conductivity spectrum and the energy-loss function spectrum were analyzed in detail. The assignments of the spectra were carried out to correlate the spectral peaks with the interband electronic transitions, which justify the reasonable part of previous empirical assignments and renew the missed or incorrect ones.展开更多
In this paper,we have reported the synthesis of FeS2 of higher band gap energy（2.75 eV） by using capping reagent and its successive application in organic-inorganic based hybrid solar cells.Hydrothermal route was ad...In this paper,we have reported the synthesis of FeS2 of higher band gap energy（2.75 eV） by using capping reagent and its successive application in organic-inorganic based hybrid solar cells.Hydrothermal route was adopted for preparing iron pyrite（FeS2） nanoparticles with capping reagent PEG-400.The quality of synthesized FeS2 material was confirmed by X-ray diffraction,field emission scanning electron microscopy,transmission electron microscopy,Fourier transform infrared,thermogravimetric analyzer,and Raman study.The optical band gap energy and electro-chemical band gap energy of the synthesized FeS2 were investigated by UV-vis spectrophotometry and cyclic voltammetry.Finally band gap engineered FeS2 has been successfully used in conjunction with conjugated polymer MEHPPV for harvesting solar energy.The energy conversion efficiency was obtained as 0.064%with a fill-factor of 0.52.展开更多
Over the recent years, the global increase of electronic wastes from electrical and electronic devices (e-wastes) has been on an alarming trend in quantity and toxicity and e-waste<span style="font-family:Verd...Over the recent years, the global increase of electronic wastes from electrical and electronic devices (e-wastes) has been on an alarming trend in quantity and toxicity and e-waste<span style="font-family:Verdana;">s</span><span style="font-family:""><span style="font-family:Verdana;"> are non-biodegradable resulting in its cumulative increase over time. Changes in technology and unrestricted regional movement of electrical devices have facilitated the generation of more e-wastes leading to high levels of air, soil and water pollution. To address these challenges, biodegradable organic components such as chitosan have been used to replace their inorganic counterparts for optoelectronic device applications. However, in-depth knowledge on how such materials can be used to tune the optical properties of their hybrid semiconductors is unrivaled. Thus, systematic studies of the interplay between the preparation methods and optical </span><span style="font-family:Verdana;">band gap and Urbach energy of such organic components are vital. This study has thus been dedicated to map out the effect of acid concentrations</span><span style="font-family:Verdana;"> during chitosan extraction on the corresponding optical band gap and Urbach energy with a view to improving its applications in optoelectronic devices. The,</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">1.0 to 2.5 molar hydrochloric acid (HCl) was used for 12 hours at room temperature during demineralization and 2.0 molar sodium hydroxide (NaOH) during deprotonation processes. The absorbance spectrum of the samples was collected by UV-Vis spectrophotometer and band gap energies were analyzed by performing Tauc’s plot. This study revealed that the energy band gap of chitosan extracted from 1 M HCl, 1.5 M HCl, 2.0 M HCl and 2.5 M HCl were 3.72 eV, 3.50 eV</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> 3.45 eV and 3.36 eV respectively. Furthermore, the Urbach energy of chitosan extracted from 展开更多
The crystal of the title compound （InP3O9, Mr = 351.73） has been prepared and structurally determined by X-ray single-crystal diffraction. It crystallizes in the monoclinic system, space group Cc with a = 13.545（6...The crystal of the title compound （InP3O9, Mr = 351.73） has been prepared and structurally determined by X-ray single-crystal diffraction. It crystallizes in the monoclinic system, space group Cc with a = 13.545（6）, b = 19.603（7）, c = 9.672（4）A, β= 127.196（4）°, V= 2045.6（14） ,A^3 and Z = 12. The compound, with a three-fold superstructure, has two kinds of infinite chains of PO4 tetrahedra along the c axis. The absorption and luminescence spectra of In（PO3）3 powder have been measured. The calculated results of crystal energy band structure by DFT indicate that the solid state is kind of insulator. What is more, the bonding and optical properties were also investigated with the CASTEP code.展开更多
A series of zinc borotellurite glass co-doped with lanthanum and silver oxide with the chemical formula of [{[(TeO2)0.7(B2O3)0.3]0.7(ZnO)0.3}0.96(La2O3)0.04]1-x(Ag2O)x where the molar frac-tion of silver oxide, x = 0....A series of zinc borotellurite glass co-doped with lanthanum and silver oxide with the chemical formula of [{[(TeO2)0.7(B2O3)0.3]0.7(ZnO)0.3}0.96(La2O3)0.04]1-x(Ag2O)x where the molar frac-tion of silver oxide, x = 0.02, 0.04, 0.06, 0.08 and 0.10 had been successfully prepared via the conventional melt-quenching technique. The structural properties of the glasses were unveiled through X-ray Diffraction (XRD) and Fourier Transform Infra-Red (FTIR) spectroscopy while optical properties of the glasses were investigated with Ultra Violet Visible (UV-Vis) spectropho-toscopy. The short range periodic atomic arrangement in the glass matrix that implies the amorphous nature of the glass was confirmed with the presence of a broad hump in the XRD pattern. On the other hand, the three absorption bands observable in the FTIR spectra had proven the existence of BO4, BO3 as well as TeO4 units in the glass network. The absorbance values retrieved from UV-Vis spectroscopy were utilized to calculate the indirect energy band gap and Urbach energy values of the fabricated glass. By employing the equations proposed by Mott and Davis, the obtained indirect energy band gap have val-ues ranging from 2.16 to 4.16 eV.The decreasing trend in indirect energy band gap and increasing Urbach energy values were related to the increasing num-ber of nonbridging oxygen (NBO) in the glass that is created from the breaking of Te-O-Te or B-O-B bonds after lanthanum as well as silver oxide are incor-porated into the zinc borotellurite glass network.展开更多
Silver doped sodium borate glasses prepared by melt-quenching technique were checked by XRD technique for their amorphous nature. It is observed that the molar volume increases with increasing Ag2O content leading to ...Silver doped sodium borate glasses prepared by melt-quenching technique were checked by XRD technique for their amorphous nature. It is observed that the molar volume increases with increasing Ag2O content leading to open struc- ture. Fourier Transform Infrared spectroscopy (FTIR) reveals the formation of BO3 and BO4 groups upon addition of silver oxide as modifier. From the Ultraviolet-Visible (UV-VIS) absorption spectra it is seen that the optical band gap increases with the increase of Ag2O content. Urbach energy is observed between 0.55 - 0.77 eV. The results obtained from molar volume, Fourier Transform Infrared spectroscopy and band gap energy measurements are in agreement with each other and nearly give the similar information about the studied glasses.展开更多
Glass system (80% B2O3 – (20 – y)% Na2CO3 – y% CdO, where y = 3, 6, 9, 12 and 15 mol%) prepared by meltquenching technique and checked by XRD technique reveals the amorphous nature of these glasses. Increases in de...Glass system (80% B2O3 – (20 – y)% Na2CO3 – y% CdO, where y = 3, 6, 9, 12 and 15 mol%) prepared by meltquenching technique and checked by XRD technique reveals the amorphous nature of these glasses. Increases in density from 2.18 to 2.82 (g/cm3) were observed with an increase in CdO content. Ultraviolet-Visible (UV-VIS) absorption spectra of polished parallel surfaces glass samples showed a decrease in the optical band gap from 3.72 to 3.59 eV with increasing CdO content. The results suggest that CdO content in glass samples plays a role as a network modifier. In addition, a correlation between the results from density, UV-VIS and FTIR measurements indicates that change in the atomic structure is due to the formation of BO4 units.展开更多
文摘采用第一性原理贋势平面波方法对（110）应变下立方相Ca_2P_（0.25）Si_（0.75）的能带结构及光学性质进行模拟计算,全面分析了应变对Ca_2P_（0.25）Si_（0.75）能带结构、光学性质的影响.计算结果表明：在92%～100%压应变范围内随着应变的逐渐增大导带向低能方向移动,价带向高能方向移动,带隙呈线性逐渐减小,但始终为直接带隙;在100%～102%张应变范围内随着应变的增加,带隙呈逐渐增大,应变达到102%直接带隙最大Eg=0.54378 e V;在102%～104%应变范围内随着应变的增加,带隙逐渐减小;当应变大于104%带隙变为间接带隙且带隙随着应变增大而减小.施加应变Ca_2P_（0.25）Si_（0.75）的介电常数、折射率均增大;施加压应变吸收系数增加,反射率减小;施加张应变吸收系数减小,反射率增加.综上所述,应变可以改变Ca_2P_（0.25）Si_（0.75）的电子结构和光学常数,是调节Ca_2P_（0.25）Si_（0.75）光电传输性能的有效手段.
基金Project supported by the Ministry of Sciences and Technology of China (2006CB601104)
文摘The electronic structure of YbB6 crystal was studied by means of density functional （GGA ＋ U） method. The calculations were performed by FLAPW method. The high accurate band structure was achieved. The correlation between the feature of the band structure and the Yb-B6 bonding in YbB6 was analyzed. On this basis, some optical constants of YbB6 such as reflectivity, dielectric function, optical conductivity, and energy-loss function were calculated. The results are in good agreement with the experiments. The real part of the optical conductivity spectrum and the energy-loss function spectrum were analyzed in detail. The assignments of the spectra were carried out to correlate the spectral peaks with the interband electronic transitions, which justify the reasonable part of previous empirical assignments and renew the missed or incorrect ones.
基金supported by University Grants Commission (UGC),Govt.of India under project 39-508/2010(SR)
文摘In this paper,we have reported the synthesis of FeS2 of higher band gap energy（2.75 eV） by using capping reagent and its successive application in organic-inorganic based hybrid solar cells.Hydrothermal route was adopted for preparing iron pyrite（FeS2） nanoparticles with capping reagent PEG-400.The quality of synthesized FeS2 material was confirmed by X-ray diffraction,field emission scanning electron microscopy,transmission electron microscopy,Fourier transform infrared,thermogravimetric analyzer,and Raman study.The optical band gap energy and electro-chemical band gap energy of the synthesized FeS2 were investigated by UV-vis spectrophotometry and cyclic voltammetry.Finally band gap engineered FeS2 has been successfully used in conjunction with conjugated polymer MEHPPV for harvesting solar energy.The energy conversion efficiency was obtained as 0.064%with a fill-factor of 0.52.
文摘Over the recent years, the global increase of electronic wastes from electrical and electronic devices (e-wastes) has been on an alarming trend in quantity and toxicity and e-waste<span style="font-family:Verdana;">s</span><span style="font-family:""><span style="font-family:Verdana;"> are non-biodegradable resulting in its cumulative increase over time. Changes in technology and unrestricted regional movement of electrical devices have facilitated the generation of more e-wastes leading to high levels of air, soil and water pollution. To address these challenges, biodegradable organic components such as chitosan have been used to replace their inorganic counterparts for optoelectronic device applications. However, in-depth knowledge on how such materials can be used to tune the optical properties of their hybrid semiconductors is unrivaled. Thus, systematic studies of the interplay between the preparation methods and optical </span><span style="font-family:Verdana;">band gap and Urbach energy of such organic components are vital. This study has thus been dedicated to map out the effect of acid concentrations</span><span style="font-family:Verdana;"> during chitosan extraction on the corresponding optical band gap and Urbach energy with a view to improving its applications in optoelectronic devices. The,</span></span><span style="font-family:""> </span><span style="font-family:Verdana;">1.0 to 2.5 molar hydrochloric acid (HCl) was used for 12 hours at room temperature during demineralization and 2.0 molar sodium hydroxide (NaOH) during deprotonation processes. The absorbance spectrum of the samples was collected by UV-Vis spectrophotometer and band gap energies were analyzed by performing Tauc’s plot. This study revealed that the energy band gap of chitosan extracted from 1 M HCl, 1.5 M HCl, 2.0 M HCl and 2.5 M HCl were 3.72 eV, 3.50 eV</span><span style="font-family:Verdana;">,</span><span style="font-family:Verdana;"> 3.45 eV and 3.36 eV respectively. Furthermore, the Urbach energy of chitosan extracted from
基金This work was supported by the National Natural Science Foundation of China (No. 90201015), Natural Science Foundation of Fujian Province (No. E0210028, and No. 2002F010) and State Key Laboratory of Structural Chemistry (No. 030060)
文摘The crystal of the title compound （InP3O9, Mr = 351.73） has been prepared and structurally determined by X-ray single-crystal diffraction. It crystallizes in the monoclinic system, space group Cc with a = 13.545（6）, b = 19.603（7）, c = 9.672（4）A, β= 127.196（4）°, V= 2045.6（14） ,A^3 and Z = 12. The compound, with a three-fold superstructure, has two kinds of infinite chains of PO4 tetrahedra along the c axis. The absorption and luminescence spectra of In（PO3）3 powder have been measured. The calculated results of crystal energy band structure by DFT indicate that the solid state is kind of insulator. What is more, the bonding and optical properties were also investigated with the CASTEP code.
文摘A series of zinc borotellurite glass co-doped with lanthanum and silver oxide with the chemical formula of [{[(TeO2)0.7(B2O3)0.3]0.7(ZnO)0.3}0.96(La2O3)0.04]1-x(Ag2O)x where the molar frac-tion of silver oxide, x = 0.02, 0.04, 0.06, 0.08 and 0.10 had been successfully prepared via the conventional melt-quenching technique. The structural properties of the glasses were unveiled through X-ray Diffraction (XRD) and Fourier Transform Infra-Red (FTIR) spectroscopy while optical properties of the glasses were investigated with Ultra Violet Visible (UV-Vis) spectropho-toscopy. The short range periodic atomic arrangement in the glass matrix that implies the amorphous nature of the glass was confirmed with the presence of a broad hump in the XRD pattern. On the other hand, the three absorption bands observable in the FTIR spectra had proven the existence of BO4, BO3 as well as TeO4 units in the glass network. The absorbance values retrieved from UV-Vis spectroscopy were utilized to calculate the indirect energy band gap and Urbach energy values of the fabricated glass. By employing the equations proposed by Mott and Davis, the obtained indirect energy band gap have val-ues ranging from 2.16 to 4.16 eV.The decreasing trend in indirect energy band gap and increasing Urbach energy values were related to the increasing num-ber of nonbridging oxygen (NBO) in the glass that is created from the breaking of Te-O-Te or B-O-B bonds after lanthanum as well as silver oxide are incor-porated into the zinc borotellurite glass network.
文摘Silver doped sodium borate glasses prepared by melt-quenching technique were checked by XRD technique for their amorphous nature. It is observed that the molar volume increases with increasing Ag2O content leading to open struc- ture. Fourier Transform Infrared spectroscopy (FTIR) reveals the formation of BO3 and BO4 groups upon addition of silver oxide as modifier. From the Ultraviolet-Visible (UV-VIS) absorption spectra it is seen that the optical band gap increases with the increase of Ag2O content. Urbach energy is observed between 0.55 - 0.77 eV. The results obtained from molar volume, Fourier Transform Infrared spectroscopy and band gap energy measurements are in agreement with each other and nearly give the similar information about the studied glasses.
文摘Glass system (80% B2O3 – (20 – y)% Na2CO3 – y% CdO, where y = 3, 6, 9, 12 and 15 mol%) prepared by meltquenching technique and checked by XRD technique reveals the amorphous nature of these glasses. Increases in density from 2.18 to 2.82 (g/cm3) were observed with an increase in CdO content. Ultraviolet-Visible (UV-VIS) absorption spectra of polished parallel surfaces glass samples showed a decrease in the optical band gap from 3.72 to 3.59 eV with increasing CdO content. The results suggest that CdO content in glass samples plays a role as a network modifier. In addition, a correlation between the results from density, UV-VIS and FTIR measurements indicates that change in the atomic structure is due to the formation of BO4 units.
