One of the methods to derive white light from light emitting diodes(LEDs)is the multi-chip white LED technology,which mixes the light from red,green and blue LEDs.Introduced is an optimal algorithm for the spectrum de...One of the methods to derive white light from light emitting diodes(LEDs)is the multi-chip white LED technology,which mixes the light from red,green and blue LEDs.Introduced is an optimal algorithm for the spectrum design of the multi-chip white LEDs in this paper.It optimizes the selection of single color LEDs and drive current controlling,so that the multi-chip white LED achieves the target correlated color temperature(CCT),as well as high luminous efficacy and good color rendering.A CCT tunable LED light source with four high-power LEDs is realized based on the above optimal design.Test results show that it maintains satisfactory color rendering and stable luminous efficacy across the whole CCT tuning range.Finally,discussed are the design improvement and the prospect of the future applications of the CCT tunable LED light source.展开更多
Improving daylighting strategy is a mandatory step to achieve visual enjoyment and energy saving in buildings. Psycho, physiological effects and energy performance have to be investigated in order to define a range of...Improving daylighting strategy is a mandatory step to achieve visual enjoyment and energy saving in buildings. Psycho, physiological effects and energy performance have to be investigated in order to define a range of different daylighting strategies, thanks to daylighting devices and climate based daylight modeling. Daylighting optimization ensures indoor healthier rooms, reduces electric light consumption and cuts the risk of glare. The best way to achieve these targets is to define users lighting needs, based on visual targets and to draw up some green measures to reduce electricity demands. Involving new climate-based daylight modeling metrics aims at defining proper illumination targets, in order to drastically reduce electrical lights, as well as reducing thermal loads deriving from cooling and HVAC （heating, ventilation and air conditioning） systems.展开更多
Hierarchically structured TiO2 microspheres were prepared at a low temperature by combining a sol-gel process with a solvothermal route and characterized by scanning electron microscopy, transmission electron microsco...Hierarchically structured TiO2 microspheres were prepared at a low temperature by combining a sol-gel process with a solvothermal route and characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. Results indicate that the phase structure of the as-prepared TiO2 products undergoes a transformation, which changes from amorphous microspheres with a smooth surface in the sol-gel process to hierarchical anatase ones consisting of nanocrystallines after the solvothermal treatment. The hierarchical anatase TiO2 microsphere shows large surface areas and good light scattering effects as the photoelectrodes for dye sensitized solar cells (DSSCs). DSSCs based on TiO2 microspheres exhibit an improvement power conversion efficiency of 6.58% and a high short current density of 13.83 mA/cm2 as compared to the commercial P25 based DSSCs with a power conversion efficiency of 4.94% and a high short current density of 10.28 mA/cm2.展开更多
The ternary blend films have been fabricated via adding 4,4'-N,N'-dicarbazole-biphenyl(CBP,a hole transport material widely used in organic light emitting diodes) into the poly(3-hexylthiophene):[6,6]-phenyl C...The ternary blend films have been fabricated via adding 4,4'-N,N'-dicarbazole-biphenyl(CBP,a hole transport material widely used in organic light emitting diodes) into the poly(3-hexylthiophene):[6,6]-phenyl C 61-butyric acid methyl ester(P3HT:PCBM).Despite the wide bandgap(3.1 eV) of the CBP,the solar cell utilizing the optimized P3HT:PCBM:CBP blend film showed an increase of 16% in power conversion efficiency and 25% in short-circuit current than the compared standard P3HT:PCBM blend film.This is attributed to the fact that the addition of the CBP could enhance the aggregation of the P3HT chains and thereby reduce the hole-electron recombination at the interface of P3HT and PCBM.We provide a simple,effective way to improve the performance of P3HT based bulk heterojunction solar cells.展开更多
Photoelectrochemical(PEC)hydrogen production is of great interest as an ideal avenue towards clean and renewable energy.However,the instability and low energy conversion efficiency of photoanodes hinder their practica...Photoelectrochemical(PEC)hydrogen production is of great interest as an ideal avenue towards clean and renewable energy.However,the instability and low energy conversion efficiency of photoanodes hinder their practical applications.Here we address these issues by introducing a hole extraction layer(HEL)which could rapidly transfer and consume photogenerated holes.The HEL is constructed by reduced graphene oxide(RGO)and other cocatalysts that enable rapid transfer and subsequent consumption of holes,respectively.Specifically,we showcase a high-stability photoanode composed of CdSeTe nanowires(CST NWs)and RGO/PdS nanoparticles(PdS NPs)based HEL.The photoanode achieves excellent photocorrosion resistance,which allows stable hydrogen evolution for>2 h at 0.5 VRHE.展开更多
Two new conjugated copolymers, PBDT-T6-TTF and PBDT-T12-TTF, were derived from a novel 4-fluorobenzoyl thienothi- ophene （TTF）. In addition, two types of benzodithiophene （BDT） units with 2,3-dihexylthienyl （T6）...Two new conjugated copolymers, PBDT-T6-TTF and PBDT-T12-TTF, were derived from a novel 4-fluorobenzoyl thienothi- ophene （TTF）. In addition, two types of benzodithiophene （BDT） units with 2,3-dihexylthienyl （T6） and 2,3-didodecylthienyl （T12） substituents, respectively, were successfully synthesized. The effect of the dual two-dimensional （2D） substitutions of the building blocks upon the optoelectronic properties of the polymers was investigated. Generally, the two polymers exhibited good solubility and broad absorption, showing similar optical band gaps of ~1.53 eV. However, PBDT-T6-TTF with its shorter alkyl chain length possessed a larger extinction coefficient in thin solid film. The highest occupied molecular orbital （HOMO） level of PBDT-T6-TTF was located at -5.38 eV while that of PBDT-T12-TTF was at -5.51 eV. In space charge-limited- current （SCLC） measurement, PBDT-T6-TTF and PBDT-T12-TTF displayed respective hole mobilities of 3.0~10-~ and 1.6x10 5 cm2 V-1 s-l. In polymer solar cells, PBDT-T6-TTF and PBDT-T12-TTF showed respective power conversion efficiencies （PCEs） of 2.86% and 1.67%. When 1,8-diiodooctane （DIO） was used as the solvent additive, the PCE of PBDT-T6-TTF was remarkably elevated to 4.85%, but the use of DIO for the PBDT-T12-TTF-blend film resulted in a lower PCE of 0.91%. Atomic force microscopy （AFM） indicated that the superior efficiency of PBDT-T6-TTF with 3% DIO （v/v） should be related to the better continuous phase separation of the blend film. Nevertheless, the morphology of the PBDT-T12-TTF deteriorated when the 3% DIO （v/v） was added. Our results suggest that the alkyl-chain length on the 2D BDT units play an important role in determining the optoelectronic properties of dual 2D BDT-TT-based polymers.展开更多
基金National High Technology Research and Development(863) Programof China(2006AA03A173)
文摘One of the methods to derive white light from light emitting diodes(LEDs)is the multi-chip white LED technology,which mixes the light from red,green and blue LEDs.Introduced is an optimal algorithm for the spectrum design of the multi-chip white LEDs in this paper.It optimizes the selection of single color LEDs and drive current controlling,so that the multi-chip white LED achieves the target correlated color temperature(CCT),as well as high luminous efficacy and good color rendering.A CCT tunable LED light source with four high-power LEDs is realized based on the above optimal design.Test results show that it maintains satisfactory color rendering and stable luminous efficacy across the whole CCT tuning range.Finally,discussed are the design improvement and the prospect of the future applications of the CCT tunable LED light source.
文摘Improving daylighting strategy is a mandatory step to achieve visual enjoyment and energy saving in buildings. Psycho, physiological effects and energy performance have to be investigated in order to define a range of different daylighting strategies, thanks to daylighting devices and climate based daylight modeling. Daylighting optimization ensures indoor healthier rooms, reduces electric light consumption and cuts the risk of glare. The best way to achieve these targets is to define users lighting needs, based on visual targets and to draw up some green measures to reduce electricity demands. Involving new climate-based daylight modeling metrics aims at defining proper illumination targets, in order to drastically reduce electrical lights, as well as reducing thermal loads deriving from cooling and HVAC （heating, ventilation and air conditioning） systems.
基金supported by the National High Technology Research and Development Program of China (Grant No. 2009AA03Z218)the National Natural Science Foundation of China (Grant No. 90923012)+1 种基金the Xi’an Applied Material Innovation Fund Project (Grant No. XA-AM-201006)the Fundamental Research Funds for the Central Universities of China
文摘Hierarchically structured TiO2 microspheres were prepared at a low temperature by combining a sol-gel process with a solvothermal route and characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction analysis. Results indicate that the phase structure of the as-prepared TiO2 products undergoes a transformation, which changes from amorphous microspheres with a smooth surface in the sol-gel process to hierarchical anatase ones consisting of nanocrystallines after the solvothermal treatment. The hierarchical anatase TiO2 microsphere shows large surface areas and good light scattering effects as the photoelectrodes for dye sensitized solar cells (DSSCs). DSSCs based on TiO2 microspheres exhibit an improvement power conversion efficiency of 6.58% and a high short current density of 13.83 mA/cm2 as compared to the commercial P25 based DSSCs with a power conversion efficiency of 4.94% and a high short current density of 10.28 mA/cm2.
基金supported by the National Natural Science Foundation of China (Grant No. 50803014)the Open Research Fund of State Key Laboratory of Polymer Physics and Chemistry,Changchun Institute of Applied Chemistry,Chinese Academy of Sciences
文摘The ternary blend films have been fabricated via adding 4,4'-N,N'-dicarbazole-biphenyl(CBP,a hole transport material widely used in organic light emitting diodes) into the poly(3-hexylthiophene):[6,6]-phenyl C 61-butyric acid methyl ester(P3HT:PCBM).Despite the wide bandgap(3.1 eV) of the CBP,the solar cell utilizing the optimized P3HT:PCBM:CBP blend film showed an increase of 16% in power conversion efficiency and 25% in short-circuit current than the compared standard P3HT:PCBM blend film.This is attributed to the fact that the addition of the CBP could enhance the aggregation of the P3HT chains and thereby reduce the hole-electron recombination at the interface of P3HT and PCBM.We provide a simple,effective way to improve the performance of P3HT based bulk heterojunction solar cells.
基金This work was supported by the National Natural Science Foundation of China(51732011,21431006,21761132008,81788101 and 11227901)the Foundation for the Innovative Research Groups of the National Natural Science Foundation of China(21521001)+2 种基金the Key Research Program of Frontier Sciences,CAS(QYZDJ-SSW-SLH036)the National Basic Research Program of China(2014CB931800)the Users with Excellence and Scientific Research Grant of Hefei Science Center of CAS(2015HSC-UE007).This work was partially carried out at the USTC Center for Micro and Nanoscale Research and Fabrication.
文摘Photoelectrochemical(PEC)hydrogen production is of great interest as an ideal avenue towards clean and renewable energy.However,the instability and low energy conversion efficiency of photoanodes hinder their practical applications.Here we address these issues by introducing a hole extraction layer(HEL)which could rapidly transfer and consume photogenerated holes.The HEL is constructed by reduced graphene oxide(RGO)and other cocatalysts that enable rapid transfer and subsequent consumption of holes,respectively.Specifically,we showcase a high-stability photoanode composed of CdSeTe nanowires(CST NWs)and RGO/PdS nanoparticles(PdS NPs)based HEL.The photoanode achieves excellent photocorrosion resistance,which allows stable hydrogen evolution for>2 h at 0.5 VRHE.
基金financially supported by the National Natural Science Foundation of China(21225418 and 51173048)the National Basic Research Program of China(2013CB834705 and 2014CB643505)GDUPS(2013)
文摘Two new conjugated copolymers, PBDT-T6-TTF and PBDT-T12-TTF, were derived from a novel 4-fluorobenzoyl thienothi- ophene （TTF）. In addition, two types of benzodithiophene （BDT） units with 2,3-dihexylthienyl （T6） and 2,3-didodecylthienyl （T12） substituents, respectively, were successfully synthesized. The effect of the dual two-dimensional （2D） substitutions of the building blocks upon the optoelectronic properties of the polymers was investigated. Generally, the two polymers exhibited good solubility and broad absorption, showing similar optical band gaps of ~1.53 eV. However, PBDT-T6-TTF with its shorter alkyl chain length possessed a larger extinction coefficient in thin solid film. The highest occupied molecular orbital （HOMO） level of PBDT-T6-TTF was located at -5.38 eV while that of PBDT-T12-TTF was at -5.51 eV. In space charge-limited- current （SCLC） measurement, PBDT-T6-TTF and PBDT-T12-TTF displayed respective hole mobilities of 3.0~10-~ and 1.6x10 5 cm2 V-1 s-l. In polymer solar cells, PBDT-T6-TTF and PBDT-T12-TTF showed respective power conversion efficiencies （PCEs） of 2.86% and 1.67%. When 1,8-diiodooctane （DIO） was used as the solvent additive, the PCE of PBDT-T6-TTF was remarkably elevated to 4.85%, but the use of DIO for the PBDT-T12-TTF-blend film resulted in a lower PCE of 0.91%. Atomic force microscopy （AFM） indicated that the superior efficiency of PBDT-T6-TTF with 3% DIO （v/v） should be related to the better continuous phase separation of the blend film. Nevertheless, the morphology of the PBDT-T12-TTF deteriorated when the 3% DIO （v/v） was added. Our results suggest that the alkyl-chain length on the 2D BDT units play an important role in determining the optoelectronic properties of dual 2D BDT-TT-based polymers.
