The strain and electron energy levels of InAs/GaAs（001） quantum dots （QDs） with a GaNAs strain compensation layer （SCL） are investigated. The results show that both the hydrostatic and biaxiai strain inside the ...The strain and electron energy levels of InAs/GaAs（001） quantum dots （QDs） with a GaNAs strain compensation layer （SCL） are investigated. The results show that both the hydrostatic and biaxiai strain inside the QDs with a GaNAs SCL are reduced compared with those with GaAs capping layers. Moreover, most of the compressive strain in the growth surface is compensated by the tensile strain of the GaNAs SCL, which implies that the influence of the strain environment of underlying QDs upon the next-layer QDs＇ growth surface is weak and suggests that the homogeneity and density of QDs can be improved. Our results are consistent with the published experimental literature. A GaNAs SCL is shown to influence the strain and band edge. As is known, the strain and the band offset affect the electronic structure, which shows that the SCL is proved to be useful to tailor the emission wavelength of QDs. Our research helps to better understand how the strain compensation technology can be applied to the growth of stacked QDs, which are useful in solar cells and laser devices.展开更多
Spherical layer quantum dots (SLQDs) attract a great deal of importance, and have various optoelectronics applications due to their outstanding optical and electrical properties. The photoluminescence (PL) and the ele...Spherical layer quantum dots (SLQDs) attract a great deal of importance, and have various optoelectronics applications due to their outstanding optical and electrical properties. The photoluminescence (PL) and the electroluminescence (EL) spectra of InAs (SLQDs) were investigated theoretically under the presence of external parameters (pressure, temperature, electric field). Existing of both the temperature and the applied electric field lead to a significant decrease in photoluminescence peak energy (red-shift), while an increase existed in presence of applied hydrostatic pressure (blue-shift). Also with increasing the quantum azimuthal number the photoluminescence peak energy increase. In addition, we found no effect on the band shape of the luminescence as a result of existing such parameters. The study indicates the importance of such parameters as fitting parameters for photoluminescence spectra.展开更多
Comparing with hot researches in absorber layer,window layer has attracted less attention in PbS quantum dot solar cells(QD SCs). Actually, the window layer plays a key role in exciton separation, charge drifting, and...Comparing with hot researches in absorber layer,window layer has attracted less attention in PbS quantum dot solar cells(QD SCs). Actually, the window layer plays a key role in exciton separation, charge drifting, and so on.Herein, ZnO window layer was systematically investigated for its roles in QD SCs performance. The physical mechanism of improved performance was also explored. It was found that the optimized ZnO films with appropriate thickness and doping concentration can balance the optical and electrical properties, and its energy band align well with the absorber layer for efficient charge extraction. Further characterizations demonstrated that the window layer optimization can help to reduce the surface defects, improve the heterojunction quality, as well as extend the depletion width. Compared with the control devices, the optimized devices have obtained an efficiency of 6.7% with an enhanced V_(oc) of 18%, J_(sc) of 21%, FF of 10%, and power conversion efficiency of 58%. The present work suggests a useful strategy to improve the device performance by optimizing the window layer besides the absorber layer.展开更多
Effects of deposition layer position film are systematically investigated. Because the and number/density on local bending of a thin deposition layer interacts with the thin film at the interface and there is an offse...Effects of deposition layer position film are systematically investigated. Because the and number/density on local bending of a thin deposition layer interacts with the thin film at the interface and there is an offset between the thin film neutral surface and the interface, the deposition layer generates not only axial stress but also bending moment. The bending moment induces an instant out-of-plane deflection of the thin film, which may or may not cause the socalled local bending. The deposition layer is modeled as a local stressor, whose location and density are demonstrated to be vital to the occurrence of local bending. The thin film rests on a viscous layer, which is governed by the Navier-Stokes equation and behaves like an elastic foundation to exert transverse forces on the thin film. The unknown feature of the axial constraint force makes the governing equation highly nonlinear even for the small deflection chse. The constraint force and film transverse deflection are solved iteratively through the governing equation and the displacement constraint equation of immovable edges. This research shows that in some special cases, the deposition density increase does not necessarily reduce the local bending. By comparing the thin film deflections of different deposition numbers and positions, we also present the guideline of strengthening or suppressing the local bending.展开更多
The effcts of various InGaAs layers on the structural and optical properties of InAs self-assembled quantum dots（ QDs ） grown by molecular-beam epitaxy （MBE） were investigated. The emission wavelength of 1317 nm ...The effcts of various InGaAs layers on the structural and optical properties of InAs self-assembled quantum dots（ QDs ） grown by molecular-beam epitaxy （MBE） were investigated. The emission wavelength of 1317 nm was obtained by embedding InAs QDs in InGaAs / GaAs quantum well. The temperature-dependent and time-resolved photoluminescence （ TDPL and TRPL ） were used to study the dynomic characteristics of carriers. InGaAs cap layer may improve the quality of quantum dots for the strain relaxation around QDs, which results in a stronger PL inteasity and an increase of PL peak lifetime up to 170 K. We found that InGaAs buffer layer may reduce the PL peak lifetime of InAs QDs, which is due to the buffer layer accelerating the carrier migration. The results also show that InGaAs cap layer can increase the temperature point when the thermal reemission and nonradiative recombination contribute significantly to the carrier dynamics.展开更多
Ink layer thickness on the printing plate greatly influences uniformity of ink transferred to the substrates,which is an important indicator of printing quality,so the study of ink layer and its thickness is important...Ink layer thickness on the printing plate greatly influences uniformity of ink transferred to the substrates,which is an important indicator of printing quality,so the study of ink layer and its thickness is important for improving the quality of printing products. Ansys CFX is used here to build a model of ink fluid adhering to lower vibrator roller,form inking roller,and printing plate for analyzing ink transferring in inking process. Ink layer thickness on each position of the model is acquired to analyze the forming mechanism of ink layer on printing plate,as well as the influence of oscillation speed of lower vibrator roller and dot area percentage of plate on ink layer thickness of printing plate. It can be concluded that,in the case of fixed ink supplying amount,ink layer thickness increases along with the increasing of oscillation speed,and decreases when the dot area percentage is getting larger and the minimum is got when the dot area percentage is 100%. At last,experiment of plate inking on print ability tester verifies the correctness of the simulation analysis.展开更多
CdS quantum dots（QDs） sensitized TiO2 nanotube arrays photoelectrodes were investigated for their photovoltaic performance of quantum dots-sensitized solar cells. The highly ordered TiO2 nanotube arrays（TNAs） were...CdS quantum dots（QDs） sensitized TiO2 nanotube arrays photoelectrodes were investigated for their photovoltaic performance of quantum dots-sensitized solar cells. The highly ordered TiO2 nanotube arrays（TNAs） were synthesized on Ti foils by anodic oxidation method. Then CdS quantum dots were deposited onto the TiO2 nanotube arrays by successive ionic layer absorption and reaction（SILAR） method to serve as the sensitizers. Cd（NO3）2 and Na2S were used as the precursor materials of Cd＋ and S2- ions, respectively. It is found that the CdS QDs sensitizer may significantly increase the light response of TiO2 nanotube arrays. With increasing CdS QDs deposition cycles, the visible light response increases. Maximum photocurrent was obtained for the QDs that have an absorption peak at about 500 nm. Under AM 1.5 G illuminations（100 mW cm^-2）, a 4.85 mA/cm^2 short circuit current density was achieved, and the maximium energy conversion efficiency of the asprepared CdS QDs-sensitized TNAs solar cells was obtained as high as 0.81% at five SILAR cycles.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60908028, 60971068, 10979065, and 61275201)the Fundamental Research Funds for the Central Universities of Ministry of Education of China (Grant No. 2011RC0402)the Program for New Century Excellent Talents in University of Ministry of Education of China (Grant No. NCET-10-0261)
文摘The strain and electron energy levels of InAs/GaAs（001） quantum dots （QDs） with a GaNAs strain compensation layer （SCL） are investigated. The results show that both the hydrostatic and biaxiai strain inside the QDs with a GaNAs SCL are reduced compared with those with GaAs capping layers. Moreover, most of the compressive strain in the growth surface is compensated by the tensile strain of the GaNAs SCL, which implies that the influence of the strain environment of underlying QDs upon the next-layer QDs＇ growth surface is weak and suggests that the homogeneity and density of QDs can be improved. Our results are consistent with the published experimental literature. A GaNAs SCL is shown to influence the strain and band edge. As is known, the strain and the band offset affect the electronic structure, which shows that the SCL is proved to be useful to tailor the emission wavelength of QDs. Our research helps to better understand how the strain compensation technology can be applied to the growth of stacked QDs, which are useful in solar cells and laser devices.
文摘Spherical layer quantum dots (SLQDs) attract a great deal of importance, and have various optoelectronics applications due to their outstanding optical and electrical properties. The photoluminescence (PL) and the electroluminescence (EL) spectra of InAs (SLQDs) were investigated theoretically under the presence of external parameters (pressure, temperature, electric field). Existing of both the temperature and the applied electric field lead to a significant decrease in photoluminescence peak energy (red-shift), while an increase existed in presence of applied hydrostatic pressure (blue-shift). Also with increasing the quantum azimuthal number the photoluminescence peak energy increase. In addition, we found no effect on the band shape of the luminescence as a result of existing such parameters. The study indicates the importance of such parameters as fitting parameters for photoluminescence spectra.
基金financially supported by the National Natural Science Foundation of China(61306137,51602114)the Research Fund for the Doctoral Program of Higher Education(20130142120075)+2 种基金the Fundamental Research Funds for the Central Universities(HUST:2016YXMS032)the Guangdong-Hong Kong joint innovation project(Grant No.2016A050503012)the Guangdong Natural Science Funds for Distinguished Young Scholars(Grant No.2015A030306044)
文摘Comparing with hot researches in absorber layer,window layer has attracted less attention in PbS quantum dot solar cells(QD SCs). Actually, the window layer plays a key role in exciton separation, charge drifting, and so on.Herein, ZnO window layer was systematically investigated for its roles in QD SCs performance. The physical mechanism of improved performance was also explored. It was found that the optimized ZnO films with appropriate thickness and doping concentration can balance the optical and electrical properties, and its energy band align well with the absorber layer for efficient charge extraction. Further characterizations demonstrated that the window layer optimization can help to reduce the surface defects, improve the heterojunction quality, as well as extend the depletion width. Compared with the control devices, the optimized devices have obtained an efficiency of 6.7% with an enhanced V_(oc) of 18%, J_(sc) of 21%, FF of 10%, and power conversion efficiency of 58%. The present work suggests a useful strategy to improve the device performance by optimizing the window layer besides the absorber layer.
基金supported by the National Natural Science Foundation of China (No.10721202)the LNM Initial Funding for Young Investigators
文摘Effects of deposition layer position film are systematically investigated. Because the and number/density on local bending of a thin deposition layer interacts with the thin film at the interface and there is an offset between the thin film neutral surface and the interface, the deposition layer generates not only axial stress but also bending moment. The bending moment induces an instant out-of-plane deflection of the thin film, which may or may not cause the socalled local bending. The deposition layer is modeled as a local stressor, whose location and density are demonstrated to be vital to the occurrence of local bending. The thin film rests on a viscous layer, which is governed by the Navier-Stokes equation and behaves like an elastic foundation to exert transverse forces on the thin film. The unknown feature of the axial constraint force makes the governing equation highly nonlinear even for the small deflection chse. The constraint force and film transverse deflection are solved iteratively through the governing equation and the displacement constraint equation of immovable edges. This research shows that in some special cases, the deposition density increase does not necessarily reduce the local bending. By comparing the thin film deflections of different deposition numbers and positions, we also present the guideline of strengthening or suppressing the local bending.
文摘The effcts of various InGaAs layers on the structural and optical properties of InAs self-assembled quantum dots（ QDs ） grown by molecular-beam epitaxy （MBE） were investigated. The emission wavelength of 1317 nm was obtained by embedding InAs QDs in InGaAs / GaAs quantum well. The temperature-dependent and time-resolved photoluminescence （ TDPL and TRPL ） were used to study the dynomic characteristics of carriers. InGaAs cap layer may improve the quality of quantum dots for the strain relaxation around QDs, which results in a stronger PL inteasity and an increase of PL peak lifetime up to 170 K. We found that InGaAs buffer layer may reduce the PL peak lifetime of InAs QDs, which is due to the buffer layer accelerating the carrier migration. The results also show that InGaAs cap layer can increase the temperature point when the thermal reemission and nonradiative recombination contribute significantly to the carrier dynamics.
基金Supported by the National Key Technology Research and Development Program of China(No.2012BAF13B05-1)National Natural Science Foundation of China(No.51105009)
文摘Ink layer thickness on the printing plate greatly influences uniformity of ink transferred to the substrates,which is an important indicator of printing quality,so the study of ink layer and its thickness is important for improving the quality of printing products. Ansys CFX is used here to build a model of ink fluid adhering to lower vibrator roller,form inking roller,and printing plate for analyzing ink transferring in inking process. Ink layer thickness on each position of the model is acquired to analyze the forming mechanism of ink layer on printing plate,as well as the influence of oscillation speed of lower vibrator roller and dot area percentage of plate on ink layer thickness of printing plate. It can be concluded that,in the case of fixed ink supplying amount,ink layer thickness increases along with the increasing of oscillation speed,and decreases when the dot area percentage is getting larger and the minimum is got when the dot area percentage is 100%. At last,experiment of plate inking on print ability tester verifies the correctness of the simulation analysis.
基金Funded by Major State Basic Research Development Program of China (973 Program) (No.2009CB939704)Key Project of Chinese Ministry of Education (No.309021)
文摘CdS quantum dots（QDs） sensitized TiO2 nanotube arrays photoelectrodes were investigated for their photovoltaic performance of quantum dots-sensitized solar cells. The highly ordered TiO2 nanotube arrays（TNAs） were synthesized on Ti foils by anodic oxidation method. Then CdS quantum dots were deposited onto the TiO2 nanotube arrays by successive ionic layer absorption and reaction（SILAR） method to serve as the sensitizers. Cd（NO3）2 and Na2S were used as the precursor materials of Cd＋ and S2- ions, respectively. It is found that the CdS QDs sensitizer may significantly increase the light response of TiO2 nanotube arrays. With increasing CdS QDs deposition cycles, the visible light response increases. Maximum photocurrent was obtained for the QDs that have an absorption peak at about 500 nm. Under AM 1.5 G illuminations（100 mW cm^-2）, a 4.85 mA/cm^2 short circuit current density was achieved, and the maximium energy conversion efficiency of the asprepared CdS QDs-sensitized TNAs solar cells was obtained as high as 0.81% at five SILAR cycles.
