Light induced changes in a-Si∶H films are investigated by transient photoconductivity.The transient photoconductivity decay data can neither be fit well by common power-law for transient photocurrent in amorphous sem...Light induced changes in a-Si∶H films are investigated by transient photoconductivity.The transient photoconductivity decay data can neither be fit well by common power-law for transient photocurrent in amorphous semiconductors,nor by stretched exponential rule for transient decay from the steady state in photoconductivity.Instead,the data are fit fairly well with a sum of two exponential functions.The results show that the long time decay is governed by deep traps rather than band tail states,and two different traps locating separately at 0.52 and 0.59eV below E _c are responsible for the two exponential functions.They are designated as negatively charged dangling bond D - centers.The light-induced changes in photoconductivity are attributed mainly to the decrease in electron lifetime caused by the increase of recombination centers after light soaking.展开更多
In this paper, a series of boron doped microcrystalline hydrogenated silicon-germanium (p-μc-Si1-xGex:H) was deposited by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) from SiH4 and G...In this paper, a series of boron doped microcrystalline hydrogenated silicon-germanium (p-μc-Si1-xGex:H) was deposited by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) from SiH4 and GeF4 mixtures. The effect of GeF4 concentration on films' composition, structure and electrical properties was studied. The results show that with the increase of GeF4 concentration, the Ge fraction x increases. The dark conductivity and crystalline volume fraction increase first, and then decrease. When the GC is 4%, p-μc-Si1-xGex:H material with high conductivity, low activation energy (σ= 1.68 S/cm, E8=0.047 eV), high crystalline volume fraction (60%) and with an average transmission coefficient over the long wave region reaching 0.9 at the thickness of 72 nm was achieved. The experimental results were discussed in detail.展开更多
With the continuous development of electronic industry, people’s demand for semiconductor materials is also increasing. How to prepare semiconductor materials with low cost, low energy consumption and high yield has ...With the continuous development of electronic industry, people’s demand for semiconductor materials is also increasing. How to prepare semiconductor materials with low cost, low energy consumption and high yield has become one of the hot spots of research. ZnTe is commonly used in the semiconductor industry due to its superior optoelectronic properties. Electrochemical deposition is one of the most frequently used methods to prepare ZnTe thin films. However,the traditional electrochemical deposition technology has many shortcomings, such as slow deposition rate and poor film quality. These hinder the large-scale promotion of zinc telluride electrochemical deposition technology. To solve the problems encountered in the preparation of semiconductor thin films by conventional electrochemical deposition, and based on the photoconductive properties of semiconductor materials themselves, the basic principles of photoelectrochemistry of semiconductor electrodes, and some characteristics of the electrochemical deposition process of semiconductor materials, the use of photoelectrochemical deposition method for the preparation of semiconductor materials was proposed. Firstly, the electrochemical behaviors(electrode reactions, nucleation growth and charge transport process) of the ZnTe electrodeposition under illumination and dark state conditions were studied. Then, the potentiostatic deposition of ZnTe was carried out under light and dark conditions. The phase structure, morphology and composition of the sediments were studied using X-ray diffractometer, scanning electron microscope and other testing methods. Finally, the photoelectrochemical deposition mechanisms were analyzed. Compared with conventional electrochemical deposition, photoelectrochemical deposition increases the current density during deposition and reduces the charge transfer impedance during ZnTe deposition process. In addition, since light illumination promotes the deposition of the difficult-to-deposit element Zn, the component ratio of ZnTe thin films prepared by photoelectrochemical deposition is closer to 1:1, making it a viable and reliable approach for ZnTe production.展开更多
A simple setup for the measurement of transmission loss in polymer thin film optical waveguides is described. A new electro-optic polymer film has been prepared. The transmission loss of the film is measured before an...A simple setup for the measurement of transmission loss in polymer thin film optical waveguides is described. A new electro-optic polymer film has been prepared. The transmission loss of the film is measured before and after corona poling. And the loss is determined to be 1.84 dB/cm and 2.14 dB/cm, respectively.展开更多
Laser processing provides highly-controlled modification and on-demand fabrication of plasmon metal nanostructures for light absorption and photothermal convention.We present the laser-induced forward tansfer(LIFT)fab...Laser processing provides highly-controlled modification and on-demand fabrication of plasmon metal nanostructures for light absorption and photothermal convention.We present the laser-induced forward tansfer(LIFT)fabrication of silver nanomembranes in control of light absorption.By varying the hatch distance,different morphologies of randomly distributed plasmon silver nanostructures were produced,leading to well-controlled light absorption levels from 11%to 81%over broadband.The anti-reflection features were maintained below 17%.Equilibrated and plain absorptions were obtained throughout all absorption levels with a maximum intensity fluctuation of±8.5%for the 225μJ cases.The 45μJ pulse energy can offer a highly equilibrated absorption at a 60%absorption level with an intensity fluctuation of±1%.Pattern transfer was also achieved on a thin tape surface.The laser-transferred characters and patterns demonstrate a localized temperature rise.A rapid temperature rising of roughly 15℃can be achieved within 1 s.The LIFT process is highly efficiently fabricated with a typical speed value of 10^(3)to 10^(5)cm^(2)/h.The results indicated that LIFT is a well-controlled and efficient method for the production of optical films with specific absorption levels.展开更多
The n-type semiconducting titanium oxide thin films are well-known as electron transporting interlayer in photovoltaic cells. The favorable characteristics of interlayers in photovoltaics are high optical transmittan...The n-type semiconducting titanium oxide thin films are well-known as electron transporting interlayer in photovoltaic cells. The favorable characteristics of interlayers in photovoltaics are high optical transmittance (T%), wide band gap energy (Eg) and high electrical conductivity (σ). Modifying titanium oxide films with metal nanoparticles would increase electrical conductivity but reduce optical band gap energy. We developed the sol-gel derived titanium suboxide (TiOx) films modified with silver (Ag) or gold (Au) or copper (Cu) nanoparticles (NPs). This study explores a tradeoff between narrowing optical band gap and enhancing electrical conductivity of nanostructured TiOx films by controlling the Au- or Ag- or Cu-NPs loading concentrations (mol%) in titania. The Au- and Cu-NPs loading concentration of 4 mol% should meet a tradeoff which yields the higher T%, wider Eg and higher compared to those of pure TiOx films. In addition, since the pure Cu is not thermodynamically stable in ambience as compared to Au and Ag, the stability of as-obtained colloidal CuNPs is also examined. A careful examination of the time evolution of surface plasmon resonance (SPR) bands of CuNPs indicates that their stability is only up to 4 h.展开更多
We report fabrication and characterization of metal-semiconductor-metal photoconductive detectors based on Al-doped ZnO thin films fabricated by radio frequency magnetron sputtering.Optical and structural properties o...We report fabrication and characterization of metal-semiconductor-metal photoconductive detectors based on Al-doped ZnO thin films fabricated by radio frequency magnetron sputtering.Optical and structural properties of the thin films were characterized using various techniques.At 6 V bias,a responsivity higher than 4 A/W in the wavelength shorter than 350 nm was obtained,and this responsibility dropped quickly and reached the noise floor in the visible region.Transient response measurement revealed that the detector had a fast photoresponse with a rise time of 9 ns and a fall time of 1.2 μs.展开更多
SnS:Ag thin films were deposited on ITO by pulse electro-deposition. They were characterized with X-ray diffraction spectroscopy and atomic force microscope. The as-deposited films have a new phase (Ag8SnS6) with g...SnS:Ag thin films were deposited on ITO by pulse electro-deposition. They were characterized with X-ray diffraction spectroscopy and atomic force microscope. The as-deposited films have a new phase (Ag8SnS6) with good crystallization and big grain size. The conductivity of the films was measured by photoelectrochemical test. It is proved that the SnS:Ag films are p-type of semiconductor. Hall measurement shows that the carrier concentration of the films increases, while their resistivity decreases after Ag-doping.展开更多
Hydrogenated microcrystalline silicon-germanium(μc-SiGe:H) films are fabricated by radio-frequency plasma-enhanced chemical vapor deposition(RF-PECVD).The optical absorption coefficient and the photosensitivity of t...Hydrogenated microcrystalline silicon-germanium(μc-SiGe:H) films are fabricated by radio-frequency plasma-enhanced chemical vapor deposition(RF-PECVD).The optical absorption coefficient and the photosensitivity of the μc-SiGe:H films increase dramatically by increasing the plasma power and deposition pressure simultaneously.Additionally,the microstructural properties of the μc-SiGe:H films are also studied.By combining Raman,Fourier transform infrared(FTIR) and X-ray fluoroscopy(XRF) measurements,it is shown that the Ge-bonding configuration and compactability of the μc-SiGe:H thin films play a crucial role in enhancing the optical absorption and optimizing the quality of the films via a significant reduction in the defect density.展开更多
Reduction of graphene oxide (GO) is a promising low-cost synthetic approach to bulk graphene, which offers an accessible route to transparent conducting films and flexible electronics. Unfortunately, the release of ...Reduction of graphene oxide (GO) is a promising low-cost synthetic approach to bulk graphene, which offers an accessible route to transparent conducting films and flexible electronics. Unfortunately, the release of oxygen-containing functional groups inevitably leaves behind vacancies and topological defects on the reduced GO sheet, and its low electrical conductivity hinders the development of practical applications. Here, we present a strategy for real-time repair of the newborn vacancies with carbon radicals produced by thermal decomposition of a suitable precursor. The sheet conductivity of thus-obtained single-layer graphene was raised more than six-fold to 350-410 S/cm (whilst retaining 〉96% transparency). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy revealed that the conductivity enhancement can be attributed to the formation of additional sp2-C structures. This method provides a simple and efficient process for obtaining highly conductive transparent graphene films.展开更多
Dip-coating is a low-cost,high-throughput technique for the deposition of organic semiconductors over large area on various substrates.Tremendous studies have been done and many parameters such as withdrawal speed,sol...Dip-coating is a low-cost,high-throughput technique for the deposition of organic semiconductors over large area on various substrates.Tremendous studies have been done and many parameters such as withdrawal speed,solvent type and solution concentration have been investigated.However,most of the depositions were ribbons or dendritic crystals with low coverage of the substrate due to the ignorance of the critical role of dynamic solution-substrate interactions during dip-coating.In this study,meniscus angle(MA)was proposed to quantify the real-time in-situ solutionsubstrate interactions during dip-coating.By proper surface treatment of the substrate,the value of MA can be tuned and centimeter-sized,continuous and highly ordered organic semiconductor thin films were achieved.The charge transport properties of the continuous thin films were investigated by the construction of organic field-effect transistors.Maximum(average)hole mobility up to 11.9(5.1)cm2V-1s-1was obtained.The average mobility was 82%higher than that of ribbon crystals,indicating the high crystallinity of the thin films.Our work reveals the critical role of dynamic solutionsubstrate interactions during dip-coating.The ability to produce large-area,continuous and highly ordered organic semiconductor thin films by dip-coating could revival the old technique for the application in various optoelectronics.展开更多
In this study, a simple spraying method is used to prepare the transparent conductive films (TCFs) based on Ag nanowires (AgNWs). Polyvinylpyrrolidone (PVP) is introduced to modify the interface of substrate. Th...In this study, a simple spraying method is used to prepare the transparent conductive films (TCFs) based on Ag nanowires (AgNWs). Polyvinylpyrrolidone (PVP) is introduced to modify the interface of substrate. The transmittance and bending performance are improved by optimizing the number of spraying times and the solution concentration and controlling the annealing time. The spraying times of 20, the concentration of 2 mg/mL and the annealing time of 10 min are chosen to fabricate the PVP/AgNWs films. The transmittance of PVP/AgNWs films is 53.4%----67.9% at 380---780 nm, and the sheet resistance is 30 f~/n which is equivalent to that of commercial indium tin oxide (1TO). During cyclic bending tests to 500 cycles with bending radius of 5 ram, the changes of resistivity are negligible. The performance of PVP/AgNW transparent electrodes has little change after being exposed to the normal environment for 1 000 h. The adhesion to polymeric substrate and the ability to endure bending stress in AgNWs network films are both significantly improved by introducing PVP. Spraying method makes AgNWs form a stratified structure on large-area polymer substrates, and the vacuum annealing method is used to weld the AgNWs together at junctions and substrates, which can improve the electrical conductivity. The experimental results indicate that PVP/AgNW transpar- ent electrodes can be used as transparent conductive electrodes in flexible organic light emitting diodes (OLEDs).展开更多
Based on the dual-phase-lagging(DPL)heat conduction model,the Cattaneo-Vernotte(CV)model and the improved CV model we investigate the one-dimensional heat conduction in gold films with nano-scale thickness exposed to ...Based on the dual-phase-lagging(DPL)heat conduction model,the Cattaneo-Vernotte(CV)model and the improved CV model we investigate the one-dimensional heat conduction in gold films with nano-scale thickness exposed to an ultra-fast laser heating.The influence of system parameters on the temperature field is explored.We find that for all the non-Fourier heat conduction models considered in this work,a larger Knudsen number normally leads to a higher temperature.For the DPL model,the large ratio of the phase lag of temperature gradient to the phase lag of heat flux reduces the maximum temperature and shortens the time for the system to reach its steady state.The CV model and the improved CV model lead to the similar thermal wave behavior of the temperature field,but the thermal wave speeds for these two models are different,especially for large Knudsen numbers.When the phase lag of temperature gradient is smaller,the difference between the DPL model and the improved CV model is not significant,but for the large phase lag of temperature gradient the difference becomes quite significant,especially for the large Knudsen number.In addition,the effect of the surface accommodation coefficient,which is a parameter in the slip boundary condition,on the temperature field of the gold film heated by ultra-fast laser pulses is investigated based on the DPL model.展开更多
The characteristic modifications are reported on the surface of polymeric waveguide film in the process of vol- ume-grating fabrication. The light from a mode-locked 76 MHz femtosecond laser with pulse duration of 200...The characteristic modifications are reported on the surface of polymeric waveguide film in the process of vol- ume-grating fabrication. The light from a mode-locked 76 MHz femtosecond laser with pulse duration of 200 fs and wavelength of 800 nm is focused normal to the surface of the sample. The surface morphology modifications are as- cribed to a fact that surface swelling occurs during the process. Periodic micro-structure is inscribed with increasing incident power. The laser-induced swelling threshold on the grating, which is higher than that of two-photon initiated photo-polymerization (TPIP) (8 mW), is verified to be about 20 mW. It is feasible to enhance the surface smoothness of integrated optics devices for further encapsulation. The variation of modulation depth is studied for different values of incident power and scan spacing. Ablation accompanied with surface swelling appears when the power is higher. By ootimizing the laser carvinR oararneters, hizhly efficient grating devices can be fabricated.展开更多
文摘Light induced changes in a-Si∶H films are investigated by transient photoconductivity.The transient photoconductivity decay data can neither be fit well by common power-law for transient photocurrent in amorphous semiconductors,nor by stretched exponential rule for transient decay from the steady state in photoconductivity.Instead,the data are fit fairly well with a sum of two exponential functions.The results show that the long time decay is governed by deep traps rather than band tail states,and two different traps locating separately at 0.52 and 0.59eV below E _c are responsible for the two exponential functions.They are designated as negatively charged dangling bond D - centers.The light-induced changes in photoconductivity are attributed mainly to the decrease in electron lifetime caused by the increase of recombination centers after light soaking.
基金National Basic Research Program of China ("973" Project, No.2006CB202602, 2006CB202603)the National Natural Science Foundation of China (No. 60437030)the Scientific Research Foundation for the Returned Overseas Chinese Scholars of the State Education Ministry.
文摘In this paper, a series of boron doped microcrystalline hydrogenated silicon-germanium (p-μc-Si1-xGex:H) was deposited by very high frequency plasma-enhanced chemical vapor deposition (VHF-PECVD) from SiH4 and GeF4 mixtures. The effect of GeF4 concentration on films' composition, structure and electrical properties was studied. The results show that with the increase of GeF4 concentration, the Ge fraction x increases. The dark conductivity and crystalline volume fraction increase first, and then decrease. When the GC is 4%, p-μc-Si1-xGex:H material with high conductivity, low activation energy (σ= 1.68 S/cm, E8=0.047 eV), high crystalline volume fraction (60%) and with an average transmission coefficient over the long wave region reaching 0.9 at the thickness of 72 nm was achieved. The experimental results were discussed in detail.
基金Project(51774341) supported by the National Natural Science Foundation of ChinaProject(2018GK4001) supported by the Science and Technology Tackling and Transformation of Major Scientific and Technological Achievements Project of Hunan Province,China。
文摘With the continuous development of electronic industry, people’s demand for semiconductor materials is also increasing. How to prepare semiconductor materials with low cost, low energy consumption and high yield has become one of the hot spots of research. ZnTe is commonly used in the semiconductor industry due to its superior optoelectronic properties. Electrochemical deposition is one of the most frequently used methods to prepare ZnTe thin films. However,the traditional electrochemical deposition technology has many shortcomings, such as slow deposition rate and poor film quality. These hinder the large-scale promotion of zinc telluride electrochemical deposition technology. To solve the problems encountered in the preparation of semiconductor thin films by conventional electrochemical deposition, and based on the photoconductive properties of semiconductor materials themselves, the basic principles of photoelectrochemistry of semiconductor electrodes, and some characteristics of the electrochemical deposition process of semiconductor materials, the use of photoelectrochemical deposition method for the preparation of semiconductor materials was proposed. Firstly, the electrochemical behaviors(electrode reactions, nucleation growth and charge transport process) of the ZnTe electrodeposition under illumination and dark state conditions were studied. Then, the potentiostatic deposition of ZnTe was carried out under light and dark conditions. The phase structure, morphology and composition of the sediments were studied using X-ray diffractometer, scanning electron microscope and other testing methods. Finally, the photoelectrochemical deposition mechanisms were analyzed. Compared with conventional electrochemical deposition, photoelectrochemical deposition increases the current density during deposition and reduces the charge transfer impedance during ZnTe deposition process. In addition, since light illumination promotes the deposition of the difficult-to-deposit element Zn, the component ratio of ZnTe thin films prepared by photoelectrochemical deposition is closer to 1:1, making it a viable and reliable approach for ZnTe production.
文摘A simple setup for the measurement of transmission loss in polymer thin film optical waveguides is described. A new electro-optic polymer film has been prepared. The transmission loss of the film is measured before and after corona poling. And the loss is determined to be 1.84 dB/cm and 2.14 dB/cm, respectively.
基金Projects(61704090, 11904177) supported by the National Natural Science Foundation of ChinaProject(KFJJ20210205) supported by the National and Local Joint Engineering Laboratory of RF Integration and Micro-Assembly Technology,Nanjing University of Posts and Telecommunications,China。
文摘Laser processing provides highly-controlled modification and on-demand fabrication of plasmon metal nanostructures for light absorption and photothermal convention.We present the laser-induced forward tansfer(LIFT)fabrication of silver nanomembranes in control of light absorption.By varying the hatch distance,different morphologies of randomly distributed plasmon silver nanostructures were produced,leading to well-controlled light absorption levels from 11%to 81%over broadband.The anti-reflection features were maintained below 17%.Equilibrated and plain absorptions were obtained throughout all absorption levels with a maximum intensity fluctuation of±8.5%for the 225μJ cases.The 45μJ pulse energy can offer a highly equilibrated absorption at a 60%absorption level with an intensity fluctuation of±1%.Pattern transfer was also achieved on a thin tape surface.The laser-transferred characters and patterns demonstrate a localized temperature rise.A rapid temperature rising of roughly 15℃can be achieved within 1 s.The LIFT process is highly efficiently fabricated with a typical speed value of 10^(3)to 10^(5)cm^(2)/h.The results indicated that LIFT is a well-controlled and efficient method for the production of optical films with specific absorption levels.
文摘The n-type semiconducting titanium oxide thin films are well-known as electron transporting interlayer in photovoltaic cells. The favorable characteristics of interlayers in photovoltaics are high optical transmittance (T%), wide band gap energy (Eg) and high electrical conductivity (σ). Modifying titanium oxide films with metal nanoparticles would increase electrical conductivity but reduce optical band gap energy. We developed the sol-gel derived titanium suboxide (TiOx) films modified with silver (Ag) or gold (Au) or copper (Cu) nanoparticles (NPs). This study explores a tradeoff between narrowing optical band gap and enhancing electrical conductivity of nanostructured TiOx films by controlling the Au- or Ag- or Cu-NPs loading concentrations (mol%) in titania. The Au- and Cu-NPs loading concentration of 4 mol% should meet a tradeoff which yields the higher T%, wider Eg and higher compared to those of pure TiOx films. In addition, since the pure Cu is not thermodynamically stable in ambience as compared to Au and Ag, the stability of as-obtained colloidal CuNPs is also examined. A careful examination of the time evolution of surface plasmon resonance (SPR) bands of CuNPs indicates that their stability is only up to 4 h.
基金supported by the National Natural Science Foundation of China (Grant No.50972007)the Beijing Municipal Natural Science Foundation (Grant No.4092035)+3 种基金the State Key Program for Basic Research of the Ministry of Science and Technology of China (Grant No.2011CB932703)the Special Items Fund of Beijing Municipal Commission of Educationthe Opened Fund of State Key Laboratory on Integrated Optoelectronicsthe National Science Fund for Distinguished Young Scholars (Grant No.60825407)
文摘We report fabrication and characterization of metal-semiconductor-metal photoconductive detectors based on Al-doped ZnO thin films fabricated by radio frequency magnetron sputtering.Optical and structural properties of the thin films were characterized using various techniques.At 6 V bias,a responsivity higher than 4 A/W in the wavelength shorter than 350 nm was obtained,and this responsibility dropped quickly and reached the noise floor in the visible region.Transient response measurement revealed that the detector had a fast photoresponse with a rise time of 9 ns and a fall time of 1.2 μs.
基金supported by the Depart ment of Science & Technology of Fujian Province(Nos.2008I0019,2006F5062,2006J0032)the Fuzhou University(Nos.K-081005,XRC-0736)~~
文摘SnS:Ag thin films were deposited on ITO by pulse electro-deposition. They were characterized with X-ray diffraction spectroscopy and atomic force microscope. The as-deposited films have a new phase (Ag8SnS6) with good crystallization and big grain size. The conductivity of the films was measured by photoelectrochemical test. It is proved that the SnS:Ag films are p-type of semiconductor. Hall measurement shows that the carrier concentration of the films increases, while their resistivity decreases after Ag-doping.
基金supported by the National Basic Research Program of China(Nos.2011CBA00705,2011CBA00706 and 2011CBA00707)the National Natural Science Foundation of China(No.61377031)+1 种基金the Natural Science Foundation of Tianjin(No.12JCQNJC01000)the Fundamental Research Funds for the Central Universities
文摘Hydrogenated microcrystalline silicon-germanium(μc-SiGe:H) films are fabricated by radio-frequency plasma-enhanced chemical vapor deposition(RF-PECVD).The optical absorption coefficient and the photosensitivity of the μc-SiGe:H films increase dramatically by increasing the plasma power and deposition pressure simultaneously.Additionally,the microstructural properties of the μc-SiGe:H films are also studied.By combining Raman,Fourier transform infrared(FTIR) and X-ray fluoroscopy(XRF) measurements,it is shown that the Ge-bonding configuration and compactability of the μc-SiGe:H thin films play a crucial role in enhancing the optical absorption and optimizing the quality of the films via a significant reduction in the defect density.
基金This work was supported by the National Natural Science Foundation of China (Grants Nos. 50802003, 20973013, 51072004, 50821061, and 20973006) and Ministry of Science and Technology of the people's Republic of China (Grants Nos. 2007CB936203, 2006CBP32602, and 2009CB929403).
文摘Reduction of graphene oxide (GO) is a promising low-cost synthetic approach to bulk graphene, which offers an accessible route to transparent conducting films and flexible electronics. Unfortunately, the release of oxygen-containing functional groups inevitably leaves behind vacancies and topological defects on the reduced GO sheet, and its low electrical conductivity hinders the development of practical applications. Here, we present a strategy for real-time repair of the newborn vacancies with carbon radicals produced by thermal decomposition of a suitable precursor. The sheet conductivity of thus-obtained single-layer graphene was raised more than six-fold to 350-410 S/cm (whilst retaining 〉96% transparency). X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy revealed that the conductivity enhancement can be attributed to the formation of additional sp2-C structures. This method provides a simple and efficient process for obtaining highly conductive transparent graphene films.
基金financial support from the National Natural Science Foundation of China(51873148,61674116 and 51633006)the Ministry of Science and Technology of China(2016YFA0202302)the Natural Science Foundation of Tianjin(18JC-YBJC18400)。
文摘Dip-coating is a low-cost,high-throughput technique for the deposition of organic semiconductors over large area on various substrates.Tremendous studies have been done and many parameters such as withdrawal speed,solvent type and solution concentration have been investigated.However,most of the depositions were ribbons or dendritic crystals with low coverage of the substrate due to the ignorance of the critical role of dynamic solution-substrate interactions during dip-coating.In this study,meniscus angle(MA)was proposed to quantify the real-time in-situ solutionsubstrate interactions during dip-coating.By proper surface treatment of the substrate,the value of MA can be tuned and centimeter-sized,continuous and highly ordered organic semiconductor thin films were achieved.The charge transport properties of the continuous thin films were investigated by the construction of organic field-effect transistors.Maximum(average)hole mobility up to 11.9(5.1)cm2V-1s-1was obtained.The average mobility was 82%higher than that of ribbon crystals,indicating the high crystallinity of the thin films.Our work reveals the critical role of dynamic solutionsubstrate interactions during dip-coating.The ability to produce large-area,continuous and highly ordered organic semiconductor thin films by dip-coating could revival the old technique for the application in various optoelectronics.
基金supported by the National Natural Science Foundation of China(No.21174036)the National High Technology Research and Development Program of China(No.2012AA011901)the National Basic Research Program of China(No.2012CB723406)
文摘In this study, a simple spraying method is used to prepare the transparent conductive films (TCFs) based on Ag nanowires (AgNWs). Polyvinylpyrrolidone (PVP) is introduced to modify the interface of substrate. The transmittance and bending performance are improved by optimizing the number of spraying times and the solution concentration and controlling the annealing time. The spraying times of 20, the concentration of 2 mg/mL and the annealing time of 10 min are chosen to fabricate the PVP/AgNWs films. The transmittance of PVP/AgNWs films is 53.4%----67.9% at 380---780 nm, and the sheet resistance is 30 f~/n which is equivalent to that of commercial indium tin oxide (1TO). During cyclic bending tests to 500 cycles with bending radius of 5 ram, the changes of resistivity are negligible. The performance of PVP/AgNW transparent electrodes has little change after being exposed to the normal environment for 1 000 h. The adhesion to polymeric substrate and the ability to endure bending stress in AgNWs network films are both significantly improved by introducing PVP. Spraying method makes AgNWs form a stratified structure on large-area polymer substrates, and the vacuum annealing method is used to weld the AgNWs together at junctions and substrates, which can improve the electrical conductivity. The experimental results indicate that PVP/AgNW transpar- ent electrodes can be used as transparent conductive electrodes in flexible organic light emitting diodes (OLEDs).
基金The National Natural Science Foundation of China(Grant No.50876054)
文摘Based on the dual-phase-lagging(DPL)heat conduction model,the Cattaneo-Vernotte(CV)model and the improved CV model we investigate the one-dimensional heat conduction in gold films with nano-scale thickness exposed to an ultra-fast laser heating.The influence of system parameters on the temperature field is explored.We find that for all the non-Fourier heat conduction models considered in this work,a larger Knudsen number normally leads to a higher temperature.For the DPL model,the large ratio of the phase lag of temperature gradient to the phase lag of heat flux reduces the maximum temperature and shortens the time for the system to reach its steady state.The CV model and the improved CV model lead to the similar thermal wave behavior of the temperature field,but the thermal wave speeds for these two models are different,especially for large Knudsen numbers.When the phase lag of temperature gradient is smaller,the difference between the DPL model and the improved CV model is not significant,but for the large phase lag of temperature gradient the difference becomes quite significant,especially for the large Knudsen number.In addition,the effect of the surface accommodation coefficient,which is a parameter in the slip boundary condition,on the temperature field of the gold film heated by ultra-fast laser pulses is investigated based on the DPL model.
基金supported by the National Natural Science Foundation of China/the Research Grants Council of Hong Kong Joint Research Scheme a grant for NSFC/RGC(No.50218001)the National Science Foundation of China(No.50173015)
文摘The characteristic modifications are reported on the surface of polymeric waveguide film in the process of vol- ume-grating fabrication. The light from a mode-locked 76 MHz femtosecond laser with pulse duration of 200 fs and wavelength of 800 nm is focused normal to the surface of the sample. The surface morphology modifications are as- cribed to a fact that surface swelling occurs during the process. Periodic micro-structure is inscribed with increasing incident power. The laser-induced swelling threshold on the grating, which is higher than that of two-photon initiated photo-polymerization (TPIP) (8 mW), is verified to be about 20 mW. It is feasible to enhance the surface smoothness of integrated optics devices for further encapsulation. The variation of modulation depth is studied for different values of incident power and scan spacing. Ablation accompanied with surface swelling appears when the power is higher. By ootimizing the laser carvinR oararneters, hizhly efficient grating devices can be fabricated.