The anomalous photovohaic effect was studied in epitaxial La0.8Sr0.2MnO3 films by laser molecular beam epitaxy. It is demonstrated that the signal polarity is reversed when the films are irradiated through the substra...The anomalous photovohaic effect was studied in epitaxial La0.8Sr0.2MnO3 films by laser molecular beam epitaxy. It is demonstrated that the signal polarity is reversed when the films are irradiated through the substrate rather than the film. Electron microdiffration and high-resolution imaging reveal that La0.8Sr0.2MnO3 thin film is epitaxially grown on the substrate, and the oriented microdomains run through the thickness of film, forming a columnar structure. Detailed investigations of the distribution of electric potential in the film surface with respect to the location of laser spot suggest that the anomalous photovoltaic response is due to an asymmetry of oriented microdomains in thin film. Under ultraviolet laser irradiation, the electron-hole pairs are excited in the manganese oxide film. The asymmetry of microdomains generates a built-in electric field and induces an asymmetric transport of the excited carriers, and hence a a photo voltage signal is obtained.展开更多
We have investigated the transport and ultraviolet photovoltaic properties of Fe3O4 thin films grown on glass substrates by facing-target sputtering technique. The nonlinear dependence of current-density on voltage su...We have investigated the transport and ultraviolet photovoltaic properties of Fe3O4 thin films grown on glass substrates by facing-target sputtering technique. The nonlinear dependence of current-density on voltage suggests that the transport process is most likely the tunnelling process and grain boundaries act as barriers. Furthermore, nonequilibrium electron-hole pairs are excited in the grains and grain boundary regions for Fe3O4 film under ultraviolet laser, since the energy gap of Fe3O4 is smaller than the ultraviolet photon energy. And then the built-in electric field near the grain boundaries will separate carriers, leading to the appearance of an instant photovoltage.展开更多
The SnO_2/SnO with an orthorhombic structure is a material known to be stable at high pressures and temperatures and expected to have new optical and electrical properties. The authors report a new finding of the infr...The SnO_2/SnO with an orthorhombic structure is a material known to be stable at high pressures and temperatures and expected to have new optical and electrical properties. The authors report a new finding of the infrared laser induced a fast photovoltaic effect arising from orthorhombic tin oxide film with an indirect band gap（~2.4 e V） which is deposited by pulsed laser deposition. The rising time of the photovoltaic signal is about 3 ns with a peak value of 4.48 mV under the pulsed laser beam with energy density 0.015 m J/mm^2. The relation between the photovoltages and laser positions along the line between two electrodes of the film is also exhibited. A possible mechanism is put forward to explain this phenomenon.All data and analyses demonstrate that the orthorhombic tin oxide with an indirect band gap could be used as a candidate for an infrared photodetector which can be operated at high pressures and temperatures.展开更多
Fast photoelectric effects have been observed in MgB2 thin film fabricated by chemical vapour deposition. The rise time was -10 ns and the full width at half-maximum was -185ns for the photovoltaic pulse when the film...Fast photoelectric effects have been observed in MgB2 thin film fabricated by chemical vapour deposition. The rise time was -10 ns and the full width at half-maximum was -185ns for the photovoltaic pulse when the film was irradiated by a 308 nm laser pulse of 25 ns in duration. X-ray diffraction and the scanning electron microscope revealed that the film was polycrystalline with preferred c-axis orientation. We propose that nonequilibrium electron-hole pairs are excited in the grains and grain boundary regions for MgB2 film under ultraviolet laser and then the built-ln electric field near the grain boundaries separates carriers, which lead to the appearance of an instant photovoltage.展开更多
This paper reports that the transient laser-induced voltages have been observed in La2/3Ca1/3MnO3 thin films on MgO （001） in the absence of an applied current. A peak voltage of - 0.15 V was detected in response to ...This paper reports that the transient laser-induced voltages have been observed in La2/3Ca1/3MnO3 thin films on MgO （001） in the absence of an applied current. A peak voltage of - 0.15 V was detected in response to 0.015J pulse of 308 nm laser. It is demonstrated that the signal polarity is reversed when the films are irradiated through the substrate rather than at the air/film interface. Off-diagonal thermoelectricity may support the inversion of the signal when the irradiation direction is reversed.展开更多
We report the photovoltaic effects of n-type topological insulator （TI） Bi2Te3 films grown on p-type Si substrates by chemical vapor deposition （CVD）. The films containing large nanoplates with a smooth surface fo...We report the photovoltaic effects of n-type topological insulator （TI） Bi2Te3 films grown on p-type Si substrates by chemical vapor deposition （CVD）. The films containing large nanoplates with a smooth surface formed on p-Si exhibit good p-n diode characteristics under dark and light illumination conditions and display a good photovoltaic effect under the broadband range from ultraviolet （UV） to near infrared （N1R） wavelengths. Under the light illumination with a wavelength of 1,000 nm, a short circuit current （Isc） of 19.2 μA and an open circuit voltage （Voc） of 235 mV are achieved. The maximum fill factor （FF） increases with a decrease in the wavelength or light density, achieving a value of 35.6% under 600 nm illumination. The photoresponse of the n-Bi2TeB/p-Si device can be effectively switched between the on and off modes in millisecond time scale. These findings are important for both the fundamental understanding and solar cell device avDlications of TI materials.展开更多
A lateral photovoltaic effect （LPE） is discovered in an LaTiO3＋8 film epitaxially grown on a （100） SrTiO3 substrate. Under the illumination of a continuous 808 nm laser beam that is focused on the LaTiO3＋δ film...A lateral photovoltaic effect （LPE） is discovered in an LaTiO3＋8 film epitaxially grown on a （100） SrTiO3 substrate. Under the illumination of a continuous 808 nm laser beam that is focused on the LaTiO3＋δ film through the SrTiO3 substrate, the open-circuit photovoltage depends linearly on the illuminated position. The sensitivity of the LPE can be modified by the bias current. The LaTiO3＋δ film shows a stable photoelectric property under the high pressure, up to 9 MPa. These results indicate that the LaTiO3＋δ films can give rise to a potentially photoelectronic device for near-infrared position-sensitive detection in high-pressure environments.展开更多
Coupled nanogenerators have been a research hotspot due to their ability to harvest a variety of forms of energy such as light,mechanical and thermal energy and achieve a stable direct current output.Ferroelectric fil...Coupled nanogenerators have been a research hotspot due to their ability to harvest a variety of forms of energy such as light,mechanical and thermal energy and achieve a stable direct current output.Ferroelectric films are frequently investigated for photovoltaic applications due to their unique photovoltaic properties and bandgap-independent photovoltage,while the flexoelectric effect is an electromechanical property commonly found in solid dielectrics.Here,we effectively construct a new form of coupled nanogenerator based on a flexible BiFeO_(3) ferroelectric film that combines both flexoelectric and photovoltaic effects to successfully harvest both light and vibration energies.This device converts an alternating current into a direct current and achieves a 6.2% charge enhancement and a 19.3%energy enhancement to achieve a multi-dimensional"1+1>2"coupling enhancement in terms of current,charge and energy.This work proposes a new approach to the coupling of multiple energy harvesting mechanisms in ferroelectric nanogenerators and provides a new strategy to enhance the transduction efficiency of flexible functional devices.展开更多
The current study presents the characterization of three types of materials after exposure to solar UV radiation. The selection of the materials is related to socio-economic aspects and rural activities in the northwe...The current study presents the characterization of three types of materials after exposure to solar UV radiation. The selection of the materials is related to socio-economic aspects and rural activities in the northwest of Argentina (a.k.a. NOA). The objective was to establish a time parameter that allows estimating the durability of the materials according to their use. One of the materials is used as a protective cover (polyethylene film) of greenhouses, which are used for crop cultivation in the area. Another material is used in photovoltaic modules (PVMs), which are used to supply energy in isolated areas and the third material is sunscreen used by people that are exposed to UV radiation during rural activities. Degradation or deterioration of the materials was monitored using different spectroscopic assays: infrared was used to detect any structural changes in the material, X-rays were used for possible changes in the crystalline structure of the material, and spectral transmittance as this property is likely to be affected by changes in the structure of the material. The results showed that degradation of polyethylene seems to be related to the diminution in transparency and the loss of mechanical resistance with increasing exposure time. The decrease in transparency of one of the layers of a PVM caused a considerable decrease in the energy generated, whereas the sunscreens with a low sun protection factor (SPF) rapidly lost their protective properties and changed their photostability properties. Our results revealed a relationship between relative transmittance loss and exposure timse, which allows estimating the stability of different materials.展开更多
In this work,we successfully prepared vertically aligned NaNbO_(3)nanotube(NN-NT)with trapezoidal shapes,in which the orthorhombic and monoclinic phases coexisted.According to the structure analysis,the NN-NT/epoxy co...In this work,we successfully prepared vertically aligned NaNbO_(3)nanotube(NN-NT)with trapezoidal shapes,in which the orthorhombic and monoclinic phases coexisted.According to the structure analysis,the NN-NT/epoxy composite film had excellent flexoelectric properties due to the lattice distortion caused by defects and irregular shape.The flexoelectric effect is the greatest in the vertical direction in the flexible NN-NT/epoxy composite film,and the flexoelectric coefficient()is 2.77×10^(−8)C·m^(−1),which is approximately 5-fold higher than that of the pure epoxy film.The photovoltaic current of the NN-NT/epoxy composite film increased from 39.9 to 71.8 nA·cm^(−2)in the direction of spontaneous polarization when the sample was bent upward due to the flexoelectricity-enhanced photovoltaic(FPV)effect.The flexoelectric effect of the NN-NT/epoxy composite film could modulate the photovoltaic response by increasing it by 80%or reducing it to 65%of the original value.This work provides a new idea for further exploration in efficient and lossless ferroelectric memory devices.展开更多
文摘The anomalous photovohaic effect was studied in epitaxial La0.8Sr0.2MnO3 films by laser molecular beam epitaxy. It is demonstrated that the signal polarity is reversed when the films are irradiated through the substrate rather than the film. Electron microdiffration and high-resolution imaging reveal that La0.8Sr0.2MnO3 thin film is epitaxially grown on the substrate, and the oriented microdomains run through the thickness of film, forming a columnar structure. Detailed investigations of the distribution of electric potential in the film surface with respect to the location of laser spot suggest that the anomalous photovoltaic response is due to an asymmetry of oriented microdomains in thin film. Under ultraviolet laser irradiation, the electron-hole pairs are excited in the manganese oxide film. The asymmetry of microdomains generates a built-in electric field and induces an asymmetric transport of the excited carriers, and hence a a photo voltage signal is obtained.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10334070 and 50371102） and China Postdoctoral Science Foundation.
文摘We have investigated the transport and ultraviolet photovoltaic properties of Fe3O4 thin films grown on glass substrates by facing-target sputtering technique. The nonlinear dependence of current-density on voltage suggests that the transport process is most likely the tunnelling process and grain boundaries act as barriers. Furthermore, nonequilibrium electron-hole pairs are excited in the grains and grain boundary regions for Fe3O4 film under ultraviolet laser, since the energy gap of Fe3O4 is smaller than the ultraviolet photon energy. And then the built-in electric field near the grain boundaries will separate carriers, leading to the appearance of an instant photovoltage.
基金Project supported by the National Natural Science Foundation of China(Grant No.60877038)
文摘The SnO_2/SnO with an orthorhombic structure is a material known to be stable at high pressures and temperatures and expected to have new optical and electrical properties. The authors report a new finding of the infrared laser induced a fast photovoltaic effect arising from orthorhombic tin oxide film with an indirect band gap（~2.4 e V） which is deposited by pulsed laser deposition. The rising time of the photovoltaic signal is about 3 ns with a peak value of 4.48 mV under the pulsed laser beam with energy density 0.015 m J/mm^2. The relation between the photovoltages and laser positions along the line between two electrodes of the film is also exhibited. A possible mechanism is put forward to explain this phenomenon.All data and analyses demonstrate that the orthorhombic tin oxide with an indirect band gap could be used as a candidate for an infrared photodetector which can be operated at high pressures and temperatures.
文摘Fast photoelectric effects have been observed in MgB2 thin film fabricated by chemical vapour deposition. The rise time was -10 ns and the full width at half-maximum was -185ns for the photovoltaic pulse when the film was irradiated by a 308 nm laser pulse of 25 ns in duration. X-ray diffraction and the scanning electron microscope revealed that the film was polycrystalline with preferred c-axis orientation. We propose that nonequilibrium electron-hole pairs are excited in the grains and grain boundary regions for MgB2 film under ultraviolet laser and then the built-ln electric field near the grain boundaries separates carriers, which lead to the appearance of an instant photovoltage.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 60576015 and 50672132）.
文摘This paper reports that the transient laser-induced voltages have been observed in La2/3Ca1/3MnO3 thin films on MgO （001） in the absence of an applied current. A peak voltage of - 0.15 V was detected in response to 0.015J pulse of 308 nm laser. It is demonstrated that the signal polarity is reversed when the films are irradiated through the substrate rather than at the air/film interface. Off-diagonal thermoelectricity may support the inversion of the signal when the irradiation direction is reversed.
文摘We report the photovoltaic effects of n-type topological insulator （TI） Bi2Te3 films grown on p-type Si substrates by chemical vapor deposition （CVD）. The films containing large nanoplates with a smooth surface formed on p-Si exhibit good p-n diode characteristics under dark and light illumination conditions and display a good photovoltaic effect under the broadband range from ultraviolet （UV） to near infrared （N1R） wavelengths. Under the light illumination with a wavelength of 1,000 nm, a short circuit current （Isc） of 19.2 μA and an open circuit voltage （Voc） of 235 mV are achieved. The maximum fill factor （FF） increases with a decrease in the wavelength or light density, achieving a value of 35.6% under 600 nm illumination. The photoresponse of the n-Bi2TeB/p-Si device can be effectively switched between the on and off modes in millisecond time scale. These findings are important for both the fundamental understanding and solar cell device avDlications of TI materials.
基金supported by the National 973 Program of China (No. 2014CB744302)the Specially Founded Program on National Key Scientific Instruments and Equipment Development (No. 2012YQ140005)
文摘A lateral photovoltaic effect （LPE） is discovered in an LaTiO3＋8 film epitaxially grown on a （100） SrTiO3 substrate. Under the illumination of a continuous 808 nm laser beam that is focused on the LaTiO3＋δ film through the SrTiO3 substrate, the open-circuit photovoltage depends linearly on the illuminated position. The sensitivity of the LPE can be modified by the bias current. The LaTiO3＋δ film shows a stable photoelectric property under the high pressure, up to 9 MPa. These results indicate that the LaTiO3＋δ films can give rise to a potentially photoelectronic device for near-infrared position-sensitive detection in high-pressure environments.
基金This work was supported by the National Natural Science Foundation of China(No.52072041)the Beijing Natural Science Foundation(No.JQ21007)the University of Chinese Academy of Sciences(No.Y8540XX2D2).
文摘Coupled nanogenerators have been a research hotspot due to their ability to harvest a variety of forms of energy such as light,mechanical and thermal energy and achieve a stable direct current output.Ferroelectric films are frequently investigated for photovoltaic applications due to their unique photovoltaic properties and bandgap-independent photovoltage,while the flexoelectric effect is an electromechanical property commonly found in solid dielectrics.Here,we effectively construct a new form of coupled nanogenerator based on a flexible BiFeO_(3) ferroelectric film that combines both flexoelectric and photovoltaic effects to successfully harvest both light and vibration energies.This device converts an alternating current into a direct current and achieves a 6.2% charge enhancement and a 19.3%energy enhancement to achieve a multi-dimensional"1+1>2"coupling enhancement in terms of current,charge and energy.This work proposes a new approach to the coupling of multiple energy harvesting mechanisms in ferroelectric nanogenerators and provides a new strategy to enhance the transduction efficiency of flexible functional devices.
文摘The current study presents the characterization of three types of materials after exposure to solar UV radiation. The selection of the materials is related to socio-economic aspects and rural activities in the northwest of Argentina (a.k.a. NOA). The objective was to establish a time parameter that allows estimating the durability of the materials according to their use. One of the materials is used as a protective cover (polyethylene film) of greenhouses, which are used for crop cultivation in the area. Another material is used in photovoltaic modules (PVMs), which are used to supply energy in isolated areas and the third material is sunscreen used by people that are exposed to UV radiation during rural activities. Degradation or deterioration of the materials was monitored using different spectroscopic assays: infrared was used to detect any structural changes in the material, X-rays were used for possible changes in the crystalline structure of the material, and spectral transmittance as this property is likely to be affected by changes in the structure of the material. The results showed that degradation of polyethylene seems to be related to the diminution in transparency and the loss of mechanical resistance with increasing exposure time. The decrease in transparency of one of the layers of a PVM caused a considerable decrease in the energy generated, whereas the sunscreens with a low sun protection factor (SPF) rapidly lost their protective properties and changed their photostability properties. Our results revealed a relationship between relative transmittance loss and exposure timse, which allows estimating the stability of different materials.
基金supported by the National Key Research&Development project from the Ministry of Science and Technology in China(No.2021YFB3200303)It was also partially supported by the National Natural Science Foundation of China(No.52172082).
文摘In this work,we successfully prepared vertically aligned NaNbO_(3)nanotube(NN-NT)with trapezoidal shapes,in which the orthorhombic and monoclinic phases coexisted.According to the structure analysis,the NN-NT/epoxy composite film had excellent flexoelectric properties due to the lattice distortion caused by defects and irregular shape.The flexoelectric effect is the greatest in the vertical direction in the flexible NN-NT/epoxy composite film,and the flexoelectric coefficient()is 2.77×10^(−8)C·m^(−1),which is approximately 5-fold higher than that of the pure epoxy film.The photovoltaic current of the NN-NT/epoxy composite film increased from 39.9 to 71.8 nA·cm^(−2)in the direction of spontaneous polarization when the sample was bent upward due to the flexoelectricity-enhanced photovoltaic(FPV)effect.The flexoelectric effect of the NN-NT/epoxy composite film could modulate the photovoltaic response by increasing it by 80%or reducing it to 65%of the original value.This work provides a new idea for further exploration in efficient and lossless ferroelectric memory devices.
