By using scanning tunneling microscope induced luminescence(STML)technique,we investigate systematically the bias-polarity dependent electroluminescence behavior of a single platinum phthalocyanine(PtPc)molecule and t...By using scanning tunneling microscope induced luminescence(STML)technique,we investigate systematically the bias-polarity dependent electroluminescence behavior of a single platinum phthalocyanine(PtPc)molecule and the electron excitation mechanisms behind.The molecule is found to emit light at both bias polarities but with different emission energies.At negative excitation bias,only the fluorescence at 637 nm is observed,which originates from the LUMOtHOMO transition of the neutral PtPc molecule and exhibits stepwise-like increase in emission intensities over three different excitation-voltage regions.Strong fluorescence in region(I)is excited by the carrier injection mechanism with holes injected into the HOMO state first;moderate fluorescence in region(II)is excited by the inelastic electron scattering mechanism;and weak fluorescence in region(III)is associated with an up-conversion process and excited by a combined carrier injection and inelastic electron scattering mechanism involving a spintriplet relay state.At positive excitation bias,more-than-one emission peaks are observed and the excitation and emission mechanisms become complicated.The sharp moleculespecific emission peak at〜911 nm is attributed to the anionic emission of PtPc-originated from the LUMO+1 tLUMO transition,whose excitation is dominated by a carrier injection mechanism with electrons first injected into the LUMO+1 or higher-lying empty orbitals.展开更多
The bilayer organic light emitting devices （OLEDs） using two common aromatic diamines as hole transporting materials （HTMs） and BBOT （2,5-bis（5-tert-butyl-2-benzoxazolyl）thiophene） as electron transporting mat...The bilayer organic light emitting devices （OLEDs） using two common aromatic diamines as hole transporting materials （HTMs） and BBOT （2,5-bis（5-tert-butyl-2-benzoxazolyl）thiophene） as electron transporting material have been prepared, in which the electroluminescent spectra are different from the fluorescent spectra of each of the constituent materials. The electroluminescence is mainly attributed to exciplex confirmed by photoluminescence and electroluminescence measurements, and the type of exicplex is deternfined in terms of the energy level diagram of the bilayer devices, By comparing the molecular structures and energy levels of TPD and NPB, it is demonstrated that the structure of a molecule as well as its energy level has an effect on the exciplex formation.展开更多
The ground and excited state properties of the [60]fullerene, diphenylbenzothiadiazole-triphenylamine （PBTDP-TPA） dyad and fullerene-diphenylbenzothiadiazole-triphenylamine （fullerene-PBTDP-TPA） triad were investi...The ground and excited state properties of the [60]fullerene, diphenylbenzothiadiazole-triphenylamine （PBTDP-TPA） dyad and fullerene-diphenylbenzothiadiazole-triphenylamine （fullerene-PBTDP-TPA） triad were investigated theoretically using density functional theory with B3LYP functional and 3-21G basis set and time-dependent density functional theory with B3LYP functional and STO-3G basis set as well as 2D and 3D real space analysis methods. The 2D site representation reveals the electron-hole coherence on excitation. The 3D transition density shows the orientation and strength of the transition dipole moment, and the 3D charge difference density gives the orientation and result of the intramolecular charge transfer. Also photoinduced intermolecular charge transfer （ICT） in PBTDP-TPA-fullerene triad are identified with 2D and 3D representations, which reveals the mechanisms of ICT in donor-bridge-acceptor triad on excitation. Besides that we also found that the direct superexchange ICT from donor to acceptor （tunneling through the bridge） strongly promotes the ICT in the donor-bridge-acceptor triad.展开更多
Un-hydrogenated Diamond-like Carbon （DLC） films were prepared by pulsed laser deposition technique at different substrate temperature. The Raman spectra, the absorption and the photoluminescence spectra were measure...Un-hydrogenated Diamond-like Carbon （DLC） films were prepared by pulsed laser deposition technique at different substrate temperature. The Raman spectra, the absorption and the photoluminescence spectra were measured. The dependence of structure and phetoluminescence properties on deposition temperature were studied in detail. The experimental results indicate that the sp^2 sites form small clus ters that consist of both olefinic chains and aromatic ring groups within the sp^3 matrix. With raising deposition temperature,the optical band gaps increase from 1.87 to 2.85 eV. The main band of photoluminescence centered at around 700nm shifts to short wavelength, and the intensity of this band increases. The photoluminescence can be attributed to carrier localization within an increasing sp^2 clusters. It was clarified that the DLC films are ordered with increasing deposition temperature.展开更多
A novel photothermal drive method was proposed. A novel photothermal micro-actuator （PTA） was developed with this method. We introduced the deflection mechanism of the asymmetric expansive arms with different widths...A novel photothermal drive method was proposed. A novel photothermal micro-actuator （PTA） was developed with this method. We introduced the deflection mechanism of the asymmetric expansive arms with different widths. When a beam of infrared laser irradiates the arms, the different increase temperature and photothermal expansion controlled by the different rates of specific surface area cause a magnified lateral deflection. A prototyping micro-actuator of 1000 μm length was manufactured by using anexcimer laser micromachining system, and using polypropylene material. Experiments have been carded out to check the feasibility of deflection, with a laser diode （650 nm） as the external power source to activate the micro-actuator. The results show that the actuator can practically generate an obvious lateral deflection without considering the size or the location of the irradiated light spot strictly. The deflection status of the micro-actuator could be controlled remotely from 0 μm to 14.33 μm by changing the laser power from 0 mW to 10 mW. This kind of novel PTA is quite simple and convenient for operation. It will be quite useful for the applications in the fields of micro/nano-technology and with large displacement/actuation force and remote controlling.展开更多
ZnS films were deposited on porous Si(PS) substrates with different porosities by pulsed laser deposition. The photolumi-nescence spectra of the samples were measured to study the effect of substrate porosity on lumin...ZnS films were deposited on porous Si(PS) substrates with different porosities by pulsed laser deposition. The photolumi-nescence spectra of the samples were measured to study the effect of substrate porosity on luminescence properties of ZnS/porous Si composites. After deposition of ZnS films,the red photoluminescence peak of porous Si shows a slight blueshift compared with as-prepared porous Si samples. With an increase of the porosity,a green emission at about 550 nm was observed which may be ascribed to the defect-center luminescence of ZnS films,and the photoluminescence of ZnS/porous Si composites is very close to white light. Good crystal structures of the samples were observed by x-ray diffraction,showing that ZnS films were grown in preferred orientation. Due to the roughness of porous Si surface,some cracks appear in ZnS films,which could be seen from scanning electron microscope images.展开更多
The major features of the display technologies for 3G cellular phone are reviewed. The comparison between their potential candidates for 3G cellular phone is given, and a detailed discussion is made on passive matrix ...The major features of the display technologies for 3G cellular phone are reviewed. The comparison between their potential candidates for 3G cellular phone is given, and a detailed discussion is made on passive matrix organic electroluminescent display technology. A novel method to improve display contrast ratio is presented. Finally several 3G phone set prototypes with OLED display panels are given as well as the market forecast.展开更多
We have investigated individual bulk-like wires of wurtzite InP using photoluminescence, photoluminescence excitation spectroscopy and transmission electron microscopy. Using two different methods we find that the top...We have investigated individual bulk-like wires of wurtzite InP using photoluminescence, photoluminescence excitation spectroscopy and transmission electron microscopy. Using two different methods we find that the top of the valence band is split, as expected theoretically. This splitting of the valence band is peculiar to wurtzite InP and does not occur in zinc blende InP. We find the energy difference between the two bands to be 40 meV.展开更多
ZnO nanorods prepared by a solution-phase method are annealed at different temperatures in oxygen ambient.The luminescence properties of the samples are investigated.In the same excitation condition,the photoluminesce...ZnO nanorods prepared by a solution-phase method are annealed at different temperatures in oxygen ambient.The luminescence properties of the samples are investigated.In the same excitation condition,the photoluminescence(PL) spectra of all samples show an ultraviolet(UV) emission and a broad strong visible emission band.The asymmetric visible emis-sion band of annealed samples has a red-shift as the annealing temperature increasing from 200 ℃ to 600 ℃ and it can be deconvoluted into two subband emissions centered at 535 nm(green emission) and 611 nm(orange-red emission) by Gaussian-fitting analysis.Analyses of PL excitation(PLE) spectra and PL spectra at different excitation wavelengths reveal that the green emission and the orange-red emission have a uniform initial state,which can be attributed to the electron transition from Zn interstitial(Zni) to oxygen vacancy(Vo) and oxygen interstitial(Oi),respectively.展开更多
基金This work is supported by the National Key R&D Program of China(No.2016YFA0200600 and No.2017YFA0303500)the National Natural Science Foundation of China,the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDB36000000)Anhui Initiative in Quantum Information Technologies.
文摘By using scanning tunneling microscope induced luminescence(STML)technique,we investigate systematically the bias-polarity dependent electroluminescence behavior of a single platinum phthalocyanine(PtPc)molecule and the electron excitation mechanisms behind.The molecule is found to emit light at both bias polarities but with different emission energies.At negative excitation bias,only the fluorescence at 637 nm is observed,which originates from the LUMOtHOMO transition of the neutral PtPc molecule and exhibits stepwise-like increase in emission intensities over three different excitation-voltage regions.Strong fluorescence in region(I)is excited by the carrier injection mechanism with holes injected into the HOMO state first;moderate fluorescence in region(II)is excited by the inelastic electron scattering mechanism;and weak fluorescence in region(III)is associated with an up-conversion process and excited by a combined carrier injection and inelastic electron scattering mechanism involving a spintriplet relay state.At positive excitation bias,more-than-one emission peaks are observed and the excitation and emission mechanisms become complicated.The sharp moleculespecific emission peak at〜911 nm is attributed to the anionic emission of PtPc-originated from the LUMO+1 tLUMO transition,whose excitation is dominated by a carrier injection mechanism with electrons first injected into the LUMO+1 or higher-lying empty orbitals.
文摘The bilayer organic light emitting devices （OLEDs） using two common aromatic diamines as hole transporting materials （HTMs） and BBOT （2,5-bis（5-tert-butyl-2-benzoxazolyl）thiophene） as electron transporting material have been prepared, in which the electroluminescent spectra are different from the fluorescent spectra of each of the constituent materials. The electroluminescence is mainly attributed to exciplex confirmed by photoluminescence and electroluminescence measurements, and the type of exicplex is deternfined in terms of the energy level diagram of the bilayer devices, By comparing the molecular structures and energy levels of TPD and NPB, it is demonstrated that the structure of a molecule as well as its energy level has an effect on the exciplex formation.
基金This work was supported by the National Natural Science Foundation of China （No.10374040, No.20703064, and No.10505001） and the Postdoctoral Science Foundation of China （No.20060390017）.
文摘The ground and excited state properties of the [60]fullerene, diphenylbenzothiadiazole-triphenylamine （PBTDP-TPA） dyad and fullerene-diphenylbenzothiadiazole-triphenylamine （fullerene-PBTDP-TPA） triad were investigated theoretically using density functional theory with B3LYP functional and 3-21G basis set and time-dependent density functional theory with B3LYP functional and STO-3G basis set as well as 2D and 3D real space analysis methods. The 2D site representation reveals the electron-hole coherence on excitation. The 3D transition density shows the orientation and strength of the transition dipole moment, and the 3D charge difference density gives the orientation and result of the intramolecular charge transfer. Also photoinduced intermolecular charge transfer （ICT） in PBTDP-TPA-fullerene triad are identified with 2D and 3D representations, which reveals the mechanisms of ICT in donor-bridge-acceptor triad on excitation. Besides that we also found that the direct superexchange ICT from donor to acceptor （tunneling through the bridge） strongly promotes the ICT in the donor-bridge-acceptor triad.
文摘Un-hydrogenated Diamond-like Carbon （DLC） films were prepared by pulsed laser deposition technique at different substrate temperature. The Raman spectra, the absorption and the photoluminescence spectra were measured. The dependence of structure and phetoluminescence properties on deposition temperature were studied in detail. The experimental results indicate that the sp^2 sites form small clus ters that consist of both olefinic chains and aromatic ring groups within the sp^3 matrix. With raising deposition temperature,the optical band gaps increase from 1.87 to 2.85 eV. The main band of photoluminescence centered at around 700nm shifts to short wavelength, and the intensity of this band increases. The photoluminescence can be attributed to carrier localization within an increasing sp^2 clusters. It was clarified that the DLC films are ordered with increasing deposition temperature.
基金the National High Technology Research and Development Program of China (Grant No.2006AA04Z237)
文摘A novel photothermal drive method was proposed. A novel photothermal micro-actuator （PTA） was developed with this method. We introduced the deflection mechanism of the asymmetric expansive arms with different widths. When a beam of infrared laser irradiates the arms, the different increase temperature and photothermal expansion controlled by the different rates of specific surface area cause a magnified lateral deflection. A prototyping micro-actuator of 1000 μm length was manufactured by using anexcimer laser micromachining system, and using polypropylene material. Experiments have been carded out to check the feasibility of deflection, with a laser diode （650 nm） as the external power source to activate the micro-actuator. The results show that the actuator can practically generate an obvious lateral deflection without considering the size or the location of the irradiated light spot strictly. The deflection status of the micro-actuator could be controlled remotely from 0 μm to 14.33 μm by changing the laser power from 0 mW to 10 mW. This kind of novel PTA is quite simple and convenient for operation. It will be quite useful for the applications in the fields of micro/nano-technology and with large displacement/actuation force and remote controlling.
基金This work was supported by the Natural Science Foundation ofShandong Province (Grant No.Y2002A09)
文摘ZnS films were deposited on porous Si(PS) substrates with different porosities by pulsed laser deposition. The photolumi-nescence spectra of the samples were measured to study the effect of substrate porosity on luminescence properties of ZnS/porous Si composites. After deposition of ZnS films,the red photoluminescence peak of porous Si shows a slight blueshift compared with as-prepared porous Si samples. With an increase of the porosity,a green emission at about 550 nm was observed which may be ascribed to the defect-center luminescence of ZnS films,and the photoluminescence of ZnS/porous Si composites is very close to white light. Good crystal structures of the samples were observed by x-ray diffraction,showing that ZnS films were grown in preferred orientation. Due to the roughness of porous Si surface,some cracks appear in ZnS films,which could be seen from scanning electron microscope images.
文摘The major features of the display technologies for 3G cellular phone are reviewed. The comparison between their potential candidates for 3G cellular phone is given, and a detailed discussion is made on passive matrix organic electroluminescent display technology. A novel method to improve display contrast ratio is presented. Finally several 3G phone set prototypes with OLED display panels are given as well as the market forecast.
文摘We have investigated individual bulk-like wires of wurtzite InP using photoluminescence, photoluminescence excitation spectroscopy and transmission electron microscopy. Using two different methods we find that the top of the valence band is split, as expected theoretically. This splitting of the valence band is peculiar to wurtzite InP and does not occur in zinc blende InP. We find the energy difference between the two bands to be 40 meV.
基金supported by the National Natural Science Foundation of China(Nos.60877029,10904109,60977035 and 60907021)the Natural Science Foundation of Tianjin(Nos.09JCYBJC01400 and 10SYSYJC28100)+1 种基金the Key Subject for Materials Physics and Chemistry of Tianjinthe Open Foundation of Key Laboratory of Luminescence and Optical Information of Ministry of Education(Nos.2010LOI02 and 2010LOI11)
文摘ZnO nanorods prepared by a solution-phase method are annealed at different temperatures in oxygen ambient.The luminescence properties of the samples are investigated.In the same excitation condition,the photoluminescence(PL) spectra of all samples show an ultraviolet(UV) emission and a broad strong visible emission band.The asymmetric visible emis-sion band of annealed samples has a red-shift as the annealing temperature increasing from 200 ℃ to 600 ℃ and it can be deconvoluted into two subband emissions centered at 535 nm(green emission) and 611 nm(orange-red emission) by Gaussian-fitting analysis.Analyses of PL excitation(PLE) spectra and PL spectra at different excitation wavelengths reveal that the green emission and the orange-red emission have a uniform initial state,which can be attributed to the electron transition from Zn interstitial(Zni) to oxygen vacancy(Vo) and oxygen interstitial(Oi),respectively.
