Semitransparent organic photovoltaics(ST-OPVs)for building integration represent a pivotal direction in the development of photovoltaic industry.Solution-processed silver nanowires(AgNWs)are considered promising candi...Semitransparent organic photovoltaics(ST-OPVs)for building integration represent a pivotal direction in the development of photovoltaic industry.Solution-processed silver nanowires(AgNWs)are considered promising candidates for transparent electrodes in semitransparent devices due to their high transparency-conductivity-efficiency merit,large-scale processability,and low cost.In this work,we develop two solution-processed organic–inorganic hybrid electrodes,named AgNWs-PD and AgNWsPC,utilizing AgNWs as the conductive framework and aliphatic amine-functionalized perylene-diimide(PDINN)as the sandwiched material,while AgNWs-PC exhibits significantly improved electrical conductivity and enhanced contact area with the underlying electron transport layer.The optimized device achieves a power conversion efficiency of 9.45%with an open circuit voltage of 0.846 V,a high filling factor of 75.4%,and an average visible transmittance(AVT)of 44.0%,delivering an outstanding light utilization efficiency(LUE)of 4.16%,which is the highest reported value for all solution-processed ST-OPVs.In addition,by coupling a 30-nm tellurium dioxide atop AgNWs-PC,the bifaciality factor of derivative devices improves from 73.7%to 99.4%,while maintaining a high bifacial LUE over 3.7%.Our results emphasize the superiority and effectiveness of PDINN-sandwiched AgNWs electrodes for highperformance and all solution-processed ST-OPVs.展开更多
Gross primary production(GPP)is a crucial indicator representing the absorption of atmospheric CO_(2) by vegetation.At present,the estimation of GPP by remote sensing is mainly based on leaf-related vegetation indexes...Gross primary production(GPP)is a crucial indicator representing the absorption of atmospheric CO_(2) by vegetation.At present,the estimation of GPP by remote sensing is mainly based on leaf-related vegetation indexes and leaf-related biophysical para-meter leaf area index(LAI),which are not completely synchronized in seasonality with GPP.In this study,we proposed chlorophyll content-based light use efficiency model(CC-LUE)to improve GPP estimates,as chlorophyll is the direct site of photosynthesis,and only the light absorbed by chlorophyll is used in the photosynthetic process.The CC-LUE model is constructed by establishing a linear correlation between satellite-derived canopy chlorophyll content(Chlcanopy)and FPAR.This method was calibrated and validated utiliz-ing 7-d averaged in-situ GPP data from 14 eddy covariance flux towers covering deciduous broadleaf forest ecosystems across five dif-ferent climate zones.Results showed a relatively robust seasonal consistency between Chlcanopy with GPP in deciduous broadleaf forests under different climatic conditions.The CC-LUE model explained 88% of the in-situ GPP seasonality for all validation site-year and 56.0% of in-situ GPP variations through the growing season,outperforming the three widely used LUE models(MODIS-GPP algorithm,Vegetation Photosynthesis Model(VPM),and the eddy covariance-light use efficiency model(EC-LUE)).Additionally,the CC-LUE model(RMSE=0.50 g C/(m^(2)·d))significantly improved the underestimation of GPP during the growing season in semi-arid region,re-markably decreasing the root mean square error of averaged growing season GPP simulation and in-situ GPP by 75.4%,73.4%,and 37.5%,compared with MOD17(RMSE=2.03 g C/(m^(2)·d)),VPM(RMSE=1.88 g C/(m^(2)·d)),and EC-LUE(RMSE=0.80 g C/(m^(2)·d))model.The chlorophyll-based method proved superior in capturing the seasonal variations of GPP in forest ecosystems,thereby provid-ing the possibility of a more precise depiction of forest seasonal carbon uptake.展开更多
We investigate the polarization-induced doping in the gradient variation of Al composition in the pAl_(0.75)Ga_(0.25)N/Al_xGa_(1-x)N hole injection layer(HIL)for deep ultraviolet light-emitting diodes(DUV-LEDs)with an...We investigate the polarization-induced doping in the gradient variation of Al composition in the pAl_(0.75)Ga_(0.25)N/Al_xGa_(1-x)N hole injection layer(HIL)for deep ultraviolet light-emitting diodes(DUV-LEDs)with an ultrathin p-GaN(4 nm)ohmic contact layer capable of emitting 277 nm.The experimental results show that the external quantum efficiency(EQE)and wall plug efficiency(WPE)of the structure graded from 0.75 to 0.55 in the HIL reach 5.49%and 5.04%,which are improved significantly by 182%and 209%,respectively,compared with the structure graded from 0.75 to 0.45,exhibiting a tremendous improvement.Both theoretical speculations and simulation results support that the larger the difference between 0.75 and x in the HIL,the higher the hole concentration that should be induced;thus,the DUV-LED has a higher internal quantum efficiency(IQE).Meanwhile,as the value of x decreases,the absorption of the DUV light emitted from the active region by the HIL is enhanced,reducing the light extraction efficiency(LEE).The IQE and LEE together affect the EQE performance of DUV-LEDs.To trade off the contradiction between the enhanced IQE and decreased LEE caused by the decrease in Al composition,the Al composition in the HIL was optimized through theoretical calculations and experiments.展开更多
By simulating with finite-difference time-domain(FDTD) method, it is proved that two kinds of new photonic crystal slab(PCS) structures could enhance the light extraction efficiency of OLED. By comparing the results, ...By simulating with finite-difference time-domain(FDTD) method, it is proved that two kinds of new photonic crystal slab(PCS) structures could enhance the light extraction efficiency of OLED. By comparing the results, the most effective PCS structure with maximum light extraction efficiency(E_ r =1.99) is got. The optimized geometric parameters and optimized performance parameters of the PCS structures are also obtained.展开更多
A facile route is developed to fabricate BiOCI porous cotton-like nanostructure by using Bi203 and hydrochlo- ric acid as raw materials. The BiOCI nanomaterial is actually hierarchically structured by numerous ultrath...A facile route is developed to fabricate BiOCI porous cotton-like nanostructure by using Bi203 and hydrochlo- ric acid as raw materials. The BiOCI nanomaterial is actually hierarchically structured by numerous ultrathin nanosheets. The nanosheets are around 50-500 nm in lateral size and 2-12 nm in thickness. High-resolution trans- mission electron microscopy and selected-area electron diffraction analyses indicate that single-crystalline BiOCl nanosheets have the predominant growth direction along [110], the bottom and top surfaces are {001} facets, and four lateral surfaces are {110} facets. The BiOCl nanosheets are dominantly enclosed by {001} facets. From the diffuse reflectance spectroscopy spectrum, the light absorption edge and band gap energy （Eg） are estimated to be 416 nm and 2.98eV, respectively. The BiOCl photocatalyst possesses superior activity for methyl orange （MO） degradation under visible light irradiation and the photodegradation efficiency is up to 91.5%/180 min. The correlation between morphology and microstructure with enhanced MO-sensitized photodegradation performance under visible light is investigated.展开更多
The light extraction efficiency caused by total internal reflection is low. Based on the analysis of the existing technology, a new design scheme is proposed in this paper to improve the light extraction efficiency. T...The light extraction efficiency caused by total internal reflection is low. Based on the analysis of the existing technology, a new design scheme is proposed in this paper to improve the light extraction efficiency. The air gap photonic crystal is embedded on the GaN-based patterned sapphire substrate, which can reduce line misalignment and improve light extraction efficiency. The internal structure of the GaN-based LED epitaxial layer is composed of an electron emission layer, a quantum well in the light-emitting recombination region, and an electron blocking layer. Experimental results show that this method significantly improves the extraction efficiency of LED light.展开更多
Physiological indices related to the efficiency (F-v/F-m) of light energy conversion in PS II and the peroxidation of membrane lipid were measured in leaves of Oryza sativa L. sp. indica rice cv. 'Shanyou 63' ...Physiological indices related to the efficiency (F-v/F-m) of light energy conversion in PS II and the peroxidation of membrane lipid were measured in leaves of Oryza sativa L. sp. indica rice cv. 'Shanyou 63' and sp. japonica rice cv. '9516'' under different temperatures and fight intensities for 4 days. No changes in F-v/F-m and membrane lipid peroxidation product (MDA) were observed, so neither photoinhibition nor photooxidation happened in both rice cultivars under moderate temperature and medium light intensity. However, F-v/F-m dropped obviously with no change in MDA contents, and photoinhibition appeared in indica rice cv. 'Shanyou 63' under medium temperature and strong light intensity. Furthermore, both photoinhibition and photooxidation were observed in two rice cultivars under chilling temperature and strong light intensity. Experiments with inhibitors under chilling temperature and strong light intensity showed that indica rice had a decrease in DI protein content and SOD activity, and the extent of inhibition of xanthophyll. cycle and nonphotochemical quenching (qN) was larger, and a higher level of MDA was observed. The photoinhibition and photooxidation in indica rice were more distinct as compared with japonica rice. The authors suggested that PS II light energy conversion efficiency (F-v/F-m) and membrane lipid peroxidation were the key indices for the detection of photooxidation.展开更多
Understanding the photon number statistics of a quantum emitter(QE)interacting with complex photonic environments is fundamental to advances in quantum optics and nanophotonics.We introduce a general theoretical frame...Understanding the photon number statistics of a quantum emitter(QE)interacting with complex photonic environments is fundamental to advances in quantum optics and nanophotonics.We introduce a general theoretical framework for calculating the modal photon number density spectrum(MPNDS)in arbitrary dielectric structures with an embedded two-level QE.We validate our approach by investigating a system composed of a two-level QE and a photonic crystal(PhC)slab with an L3 cavity and a waveguide,finding that the MPNDS exhibits significant changes in both waveguide and background radiative channels as the interaction between the QE and modal field transitions from weak coupling to strong coupling.We observe that the number of photons guided along the waveguide shows a strong dependence on the QE’s transition frequency and transition dipole moment,but demonstrates robustness to the transition dipole moment when the transition frequency approaches the waveguide cutoff frequency.Our work allows for the determination and tailoring of light emission characteristics across diverse radiative channels in complex photonic environments.展开更多
Soil moisture is a major limiting factor for plant growth on shell ridge islands in the Yellow River Delta. However, it is difficult to carry out situ experiment to study dominant plant photosynthesis physiological on...Soil moisture is a major limiting factor for plant growth on shell ridge islands in the Yellow River Delta. However, it is difficult to carry out situ experiment to study dominant plant photosynthesis physiological on the shell ridge islands under extreme soil water stress. To evaluate the adaptability of plants to light and moisture variations under extreme soil moisture conditions present on these islands, we measured photosynthetic gas exchange process, chlorophyll fluorescence, and stem sap flow variables for 3-year-old trees of Tamarix chinensis Lour, a restoration species on these islands, subjected to three types of soil water levels： waterlogging stress （WS）, alternating dry-wet （WD）, and severe drought stress （SS） to inform decisions on its planting and management on shell ridge islands. Gas exchange, chlorophyll fluorescence, and stem sap flow in T. chinensis were then measured. Net photosynthetic rate （PN）, transpiration rate （E）, and water use efficiency （WUE） were similar under WS and alternating dry-wet conditions, but their mean E and WUE differed significantly （P 〈 0.05）. Under SS, the PN, E and WErE of T. chinensis leaves varied slightly, and mean PN, E and WUE were all low. Apparent quantum efficiency （AQY）, light compensation point （LCP）, light saturation point （LSP）, and maximum net photosynthetic rate （PNmax） of leaves were not significantly different （P 〉 0.05） under WS and dry-wet conditions; however, under extreme drought stress, compared with the dry-wet conditions, LCP was higher, Lsp was lower, and AQy and PNmax were both at the lowest level. Therefore, drought stress weakened light adaptability of leaves, and the efficiency of light transformation was poorer. （3） Maximum photochemical efficiency （Fv/Fm） and the actual photochemical efficiency （ΦPSII） were similar under waterlogged stress and dry-wet conditions, indicating a similar healthy photosynthetic apparatus and photosynthetic reaction cen- ter activity, respectively. Under SS, Fv/Fm was 0.631, and the coefficient of non-photochemical quenching （NpQ） was 0.814, which indicated that while the photosynthetic mechanism was damaged, the absorbed light energy was mainly dissipated in the form of heat, and the potential photosynthetic productivity was significantly reduced. The daily cumulants of sap flow of T. chinensis under drywet alternation and severe drought stress were. 22.25 and 63.97% higher, respectively, than under waterlogging stress. Daily changes in sap flow velocity for T. chinensis differed under the three soil water levels. Stem sap flow was weak at night under severe drought stress. Under drywet alternation, daytime average stem sap flow velocity was the highest, and night stem flow accounted for 10.26% of the day cumulants, while under waterlogged stress, the average nightly stem flow velocity was the highest, accounting for 31.82% of the day cumulants. These results provide important information for regional vegetation restoration and ecological reconstruction.展开更多
In this work,we design and fabricate a deep ultraviolet(DUV)light-emitting array consisting of 10×10 micro-LEDs(μ-LEDs)with each device having 20μm in diameter.Strikingly,the array demonstrates a significant en...In this work,we design and fabricate a deep ultraviolet(DUV)light-emitting array consisting of 10×10 micro-LEDs(μ-LEDs)with each device having 20μm in diameter.Strikingly,the array demonstrates a significant enhancement of total light output power by nearly 52%at the injection current of 100 mA,in comparison to a conventional large LED chip whose emitting area is the same as the array.A much higher(~22%)peak external quantum efficiency,as well as a smaller efficiency droop forμ-LED array,was also achieved.The numerical calculation reveals that the performance boost can be attributed to the higher light extraction efficiency at the edge of eachμ-LED.Additionally,the far-field pattern measurement shows that theμ-LED array possesses a better forward directionality of emission.These findings shed light on the enhancement of the DUV LEDs performance and provide new insights in controlling the light behavior of theμ-LEDs.展开更多
Counter beam lighting was introduced as well as transverse symmetrical lighting and longitudinal symmetrical lighting.Simulation experiments were carried out by using DIAlux lighting software for the above three light...Counter beam lighting was introduced as well as transverse symmetrical lighting and longitudinal symmetrical lighting.Simulation experiments were carried out by using DIAlux lighting software for the above three lighting methods.The results show that counter beam lighting is more reasonable to be adopted in the tunnel entrance zone because its threshold increment of disability glare is greater.Counter beam lighting can improve the background luminance of the obstacles and lighting efficiency compared with transverse symmetrical lighting and longitudinal symmetrical lighting.Therefore,tunnel lighting energy-saving can be achieved by reducing the road luminance demands and luminaries power.Longitudinal symmetrical lighting is conducive to the large luminaries spacing in the tunnel internal zone;so power consumption can be reduced by decreasing the number of luminaries used.Tunnel walls are unsuitable to pave with smooth or bright material.Installation height of the luminaries has less effect on counter beam lighting.展开更多
ABSTRACT Embedding submicrocavities is an effective approach to improve the light out-coupling efficiency(LOCE)for planar perovskite light-emitting diodes(PeLEDs).In this work,we employ phenethylammonium iodide(PEAI)t...ABSTRACT Embedding submicrocavities is an effective approach to improve the light out-coupling efficiency(LOCE)for planar perovskite light-emitting diodes(PeLEDs).In this work,we employ phenethylammonium iodide(PEAI)to trigger the Ostwald ripening for the downward recrystallization of perovskite,resulting in spontaneous formation of buried submicrocavities as light output coupler.The simulation suggests the buried submicrocavities can improve the LOCE from 26.8 to 36.2%for near-infrared light.Therefore,PeLED yields peak external quantum efficiency(EQE)increasing from 17.3%at current density of 114 mA cm^(−2)to 25.5%at current density of 109 mA cm^(−2)and a radiance increasing from 109 to 487 W sr^(−1)m^(−2)with low rolling-off.The turn-on voltage decreased from 1.25 to 1.15 V at 0.1 W sr^(−1)m^(−2).Besides,downward recrystallization process slightly reduces the trap density from 8.90×10^(15)to 7.27×10^(15)cm^(−3).This work provides a self-assembly method to integrate buried output coupler for boosting the performance of PeLEDs.展开更多
Available light under forest canopies includes two components, diffuse light and direct light (sunflecks), and is characterized as low and highly dynamic. Understory habitats under different forest types experience di...Available light under forest canopies includes two components, diffuse light and direct light (sunflecks), and is characterized as low and highly dynamic. Understory habitats under different forest types experience different light conditions. Sunflecks as a critical resource for understory plants have great importance on carbon gain of understory plants. Under the light-limiting habitat, understory plants exhibit a high light utilization efficiency attributed by a post-illumination CO2 uptake. Although different species have different photosynthetic responses, shade plants appear to be acclimated to respond more quickly and efficiently to sunflecks. This acclimation includes a faster induction, relatively lower rate of induction loss, lower photosynthetic compensation point, and higher water use efficiency. The process that shade plants harvest light energy is not well known. Studies of photosynthetic responses to sunflecks in natural conditions are rare. Little is known about constraints on sunfleck utilization, which may change seasonally. Extensive field studies in conjunction with laboratory investigations will be needed to further understand potential and actual constraints on sunfleck utilization. Most studies on photosynthetic responses to fluctuating light condition were done in the level of leaves. Fluctuating light utilization on the basis of whole plants and populations presents future challenges to ecologists.展开更多
Because of its very low light extraction efficiency(LEE),LED is limited to be widely used under the condition of the internal quantum efficiency which up to 90%.In order to fullfill the design of a more efficient GaN-...Because of its very low light extraction efficiency(LEE),LED is limited to be widely used under the condition of the internal quantum efficiency which up to 90%.In order to fullfill the design of a more efficient GaN-based blue light LED,the model including deeply etched surface photonic crystals(PhCs)LED is discussed using mode analysis method from light waveguide theory.The distributions of all order modes in GaN layer are obtained by the effective index approximation.The light extraction efficiencies are also calculated by finite-difference time-domain method(FDTD).The emulated results fully coincide with the former analysis.Because the manufacture of the surface photonic crystal is feasible,the work can be very meaningful to design and manufacture the high efficiency GaN-based blue light LED in factory for a large amount.展开更多
Currently, daylighting ducts system is widely used as a daylighting device. Generally, daylighting duct system efficiently takes light from outside during the day, and conveys daylight to required location through lig...Currently, daylighting ducts system is widely used as a daylighting device. Generally, daylighting duct system efficiently takes light from outside during the day, and conveys daylight to required location through light duct manufactured by high reflectance mirror. Daylighting duct system can convey daylight to underground space that has no windows opening to external space. Daylighting system is composed of light collection part, light guide part and light emission part. Efficiency of daylighting system is depending on type of each part used in the system. However, it is very difficult to estimate exact light flow in the system considering type of the parts. Authors performed measurement experiments to make clear the light flow with real-size model and miniature model of daylighting duct system. We discussed effect of type of the parts on efficiency of daylighting duct system.展开更多
Highly efficient and stable hybrid white organic light-emitting diodes （HWOLEDs） with a mixed bipolar interlayer between fluorescent blue and phosphorescent yellow emitting layers are demonstrated. The bipolar inter...Highly efficient and stable hybrid white organic light-emitting diodes （HWOLEDs） with a mixed bipolar interlayer between fluorescent blue and phosphorescent yellow emitting layers are demonstrated. The bipolar interlayer is a mixture of p-type diphenyl （l0-phenyl-lOH-spiro [acridine-9,9＇-fluoren]-3Lyl） phosphine oxide and n-type 2＇,2- （1,3,5-benzinetriyl）-tris（1-phenyl-l-H-benzimidazole）. The electroluminance and Commission Internationale de l＇Eclairage （CIE1931） coordinates＇ characteristics can be modulated easily by adjusting the ratio of the hole- predominated material to the electron-predominated material in the interlayer. The hybrid WOLED with a p-type：n-type ratio of 1：3 shows a maximum current efficiency and power efficiency of 61.1 ed/A and 55.8 lm/W, respectively, with warm white CIE coordinates of （0.34, 0.43）. The excellent efficiency and adaptive CIE coordi- nates are attributed to the mixed interlayer with improved charge carrier balance, optimized exciton distribution, and enhanced harvesting of singlet and triplet excitons.展开更多
240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated.Then,the external quantum efficiency(EQE)and light extraction efficiency(LEE)are systematically investigated by comparing size and edge ef...240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated.Then,the external quantum efficiency(EQE)and light extraction efficiency(LEE)are systematically investigated by comparing size and edge effects.Here,it is revealed that the peak optical output power increases by 81.83%with the size shrinking from 50.0 to 25.0μm.Thereinto,the LEE increases by 26.21%and the LEE enhancement mainly comes from the sidewall light extraction.Most notably,transversemagnetic(TM)mode light intensifies faster as the size shrinks due to the tilted mesa side-wall and Al reflector design.However,when it turns to 12.5μm sized micro-LEDs,the output power is lower than 25.0μm sized ones.The underlying mechanism is that even though protected by SiO2 passivation,the edge effect which leads to current leakage and Shockley-Read-Hall(SRH)recombination deteriorates rapidly with the size further shrinking.Moreover,the ratio of the p-contact area to mesa area is much lower,which deteriorates the p-type current spreading at the mesa edge.These findings show a role of thumb for the design of high efficiency micro-LEDs with wavelength below 250 nm,which will pave the way for wide applications of deep ultraviolet(DUV)micro-LEDs.展开更多
Semitransparent organic solar cells(ST-OSCs)have garnered considerable attention as promising renewable energy technology for integrating photovoltaics into buildings.However,there is a trade-off between power convers...Semitransparent organic solar cells(ST-OSCs)have garnered considerable attention as promising renewable energy technology for integrating photovoltaics into buildings.However,there is a trade-off between power conversion efficiency(PCE)and average visible transmittance(AVT),which hinders the achievement of a high light utilization efficiency(LUE).In this study,we propose a valuable method to address this challenge by replacing the transparent top electrode,Ag,with a 20 nm layer of Au.The ST-OSCs based on the 20 nm Au electrode demonstrate superior exciton extraction,more efficient charge collection,and higher color-rendering index(CRI)due to their smoother surface,higher conductivity,and enhanced visible light transmittance,resulting in a significantly higher PCE of 13.67%and an enhanced AVT of 30.17%,contributing to a high LUE of 4.15%.Additionally,optically transparent dielectric layers,applied on the front and back sides of the ST-OSCs to further boost performance,delivered an impressive LUE of 4.93%,with PCE and AVT values reaching 14.44%and 34.12%,respectively.Notably,the champion ST-OSCs also exhibited a favorable CRI value of 93.37.These achievements represent the bestperforming ST-OSCs to date with both high LUE and CRI and hold significant implications for the prospective commercialization of ST-OSCs.展开更多
In this paper, a new illumination system with ultra high performance (UHP) lamp is proposed for projection display. Parabolic reflector (PR) and compound parabolic retro-reflector (CPR) were jointly used to collect an...In this paper, a new illumination system with ultra high performance (UHP) lamp is proposed for projection display. Parabolic reflector (PR) and compound parabolic retro-reflector (CPR) were jointly used to collect and collimate the light generated from UHP lamp. A polarization converter system (PCS) was used to increase the light efficiency of the projection display system. A beam transformer between PCS and 2f imaging systems was directly used to make the illumination meet the requirement of projection display system. With the consideration of the loss of reflection, the light efficiency in this projection display system was estimated to be 15.6%.展开更多
基金financially supported by the National Natural Science Foundation of China(21905137)the Research Grants Council of Hong Kong(15307922,C5037-18G,C4005-22Y)+1 种基金RGC Senior Research Fellowship Scheme(SRFS2223-5S01)the Hong Kong Polytechnic University:Sir Sze-yuen Chung Endowed Professorship Fund(8-8480)。
文摘Semitransparent organic photovoltaics(ST-OPVs)for building integration represent a pivotal direction in the development of photovoltaic industry.Solution-processed silver nanowires(AgNWs)are considered promising candidates for transparent electrodes in semitransparent devices due to their high transparency-conductivity-efficiency merit,large-scale processability,and low cost.In this work,we develop two solution-processed organic–inorganic hybrid electrodes,named AgNWs-PD and AgNWsPC,utilizing AgNWs as the conductive framework and aliphatic amine-functionalized perylene-diimide(PDINN)as the sandwiched material,while AgNWs-PC exhibits significantly improved electrical conductivity and enhanced contact area with the underlying electron transport layer.The optimized device achieves a power conversion efficiency of 9.45%with an open circuit voltage of 0.846 V,a high filling factor of 75.4%,and an average visible transmittance(AVT)of 44.0%,delivering an outstanding light utilization efficiency(LUE)of 4.16%,which is the highest reported value for all solution-processed ST-OPVs.In addition,by coupling a 30-nm tellurium dioxide atop AgNWs-PC,the bifaciality factor of derivative devices improves from 73.7%to 99.4%,while maintaining a high bifacial LUE over 3.7%.Our results emphasize the superiority and effectiveness of PDINN-sandwiched AgNWs electrodes for highperformance and all solution-processed ST-OPVs.
基金Under the auspices of the National Key Research and Development Program of China(No.2019YFA0606603)。
文摘Gross primary production(GPP)is a crucial indicator representing the absorption of atmospheric CO_(2) by vegetation.At present,the estimation of GPP by remote sensing is mainly based on leaf-related vegetation indexes and leaf-related biophysical para-meter leaf area index(LAI),which are not completely synchronized in seasonality with GPP.In this study,we proposed chlorophyll content-based light use efficiency model(CC-LUE)to improve GPP estimates,as chlorophyll is the direct site of photosynthesis,and only the light absorbed by chlorophyll is used in the photosynthetic process.The CC-LUE model is constructed by establishing a linear correlation between satellite-derived canopy chlorophyll content(Chlcanopy)and FPAR.This method was calibrated and validated utiliz-ing 7-d averaged in-situ GPP data from 14 eddy covariance flux towers covering deciduous broadleaf forest ecosystems across five dif-ferent climate zones.Results showed a relatively robust seasonal consistency between Chlcanopy with GPP in deciduous broadleaf forests under different climatic conditions.The CC-LUE model explained 88% of the in-situ GPP seasonality for all validation site-year and 56.0% of in-situ GPP variations through the growing season,outperforming the three widely used LUE models(MODIS-GPP algorithm,Vegetation Photosynthesis Model(VPM),and the eddy covariance-light use efficiency model(EC-LUE)).Additionally,the CC-LUE model(RMSE=0.50 g C/(m^(2)·d))significantly improved the underestimation of GPP during the growing season in semi-arid region,re-markably decreasing the root mean square error of averaged growing season GPP simulation and in-situ GPP by 75.4%,73.4%,and 37.5%,compared with MOD17(RMSE=2.03 g C/(m^(2)·d)),VPM(RMSE=1.88 g C/(m^(2)·d)),and EC-LUE(RMSE=0.80 g C/(m^(2)·d))model.The chlorophyll-based method proved superior in capturing the seasonal variations of GPP in forest ecosystems,thereby provid-ing the possibility of a more precise depiction of forest seasonal carbon uptake.
基金the National Natural Science Foundation of China(Grant No.62104085)the Innovation/Entrepreneurship Program of Jiangsu Province,China(Grant No.JSSCTD202146)。
文摘We investigate the polarization-induced doping in the gradient variation of Al composition in the pAl_(0.75)Ga_(0.25)N/Al_xGa_(1-x)N hole injection layer(HIL)for deep ultraviolet light-emitting diodes(DUV-LEDs)with an ultrathin p-GaN(4 nm)ohmic contact layer capable of emitting 277 nm.The experimental results show that the external quantum efficiency(EQE)and wall plug efficiency(WPE)of the structure graded from 0.75 to 0.55 in the HIL reach 5.49%and 5.04%,which are improved significantly by 182%and 209%,respectively,compared with the structure graded from 0.75 to 0.45,exhibiting a tremendous improvement.Both theoretical speculations and simulation results support that the larger the difference between 0.75 and x in the HIL,the higher the hole concentration that should be induced;thus,the DUV-LED has a higher internal quantum efficiency(IQE).Meanwhile,as the value of x decreases,the absorption of the DUV light emitted from the active region by the HIL is enhanced,reducing the light extraction efficiency(LEE).The IQE and LEE together affect the EQE performance of DUV-LEDs.To trade off the contradiction between the enhanced IQE and decreased LEE caused by the decrease in Al composition,the Al composition in the HIL was optimized through theoretical calculations and experiments.
文摘By simulating with finite-difference time-domain(FDTD) method, it is proved that two kinds of new photonic crystal slab(PCS) structures could enhance the light extraction efficiency of OLED. By comparing the results, the most effective PCS structure with maximum light extraction efficiency(E_ r =1.99) is got. The optimized geometric parameters and optimized performance parameters of the PCS structures are also obtained.
基金Supported by the International Science and Technology Cooperation Program of China under Grant No 2014DFA60150the National Natural Science Foundation of China under Grant Nos 51172113 and 51373086the Taishan Scholar Overseas Distinguished Professorship Program from the Shandong Provincial Government
文摘A facile route is developed to fabricate BiOCI porous cotton-like nanostructure by using Bi203 and hydrochlo- ric acid as raw materials. The BiOCI nanomaterial is actually hierarchically structured by numerous ultrathin nanosheets. The nanosheets are around 50-500 nm in lateral size and 2-12 nm in thickness. High-resolution trans- mission electron microscopy and selected-area electron diffraction analyses indicate that single-crystalline BiOCl nanosheets have the predominant growth direction along [110], the bottom and top surfaces are {001} facets, and four lateral surfaces are {110} facets. The BiOCl nanosheets are dominantly enclosed by {001} facets. From the diffuse reflectance spectroscopy spectrum, the light absorption edge and band gap energy （Eg） are estimated to be 416 nm and 2.98eV, respectively. The BiOCl photocatalyst possesses superior activity for methyl orange （MO） degradation under visible light irradiation and the photodegradation efficiency is up to 91.5%/180 min. The correlation between morphology and microstructure with enhanced MO-sensitized photodegradation performance under visible light is investigated.
文摘The light extraction efficiency caused by total internal reflection is low. Based on the analysis of the existing technology, a new design scheme is proposed in this paper to improve the light extraction efficiency. The air gap photonic crystal is embedded on the GaN-based patterned sapphire substrate, which can reduce line misalignment and improve light extraction efficiency. The internal structure of the GaN-based LED epitaxial layer is composed of an electron emission layer, a quantum well in the light-emitting recombination region, and an electron blocking layer. Experimental results show that this method significantly improves the extraction efficiency of LED light.
文摘Physiological indices related to the efficiency (F-v/F-m) of light energy conversion in PS II and the peroxidation of membrane lipid were measured in leaves of Oryza sativa L. sp. indica rice cv. 'Shanyou 63' and sp. japonica rice cv. '9516'' under different temperatures and fight intensities for 4 days. No changes in F-v/F-m and membrane lipid peroxidation product (MDA) were observed, so neither photoinhibition nor photooxidation happened in both rice cultivars under moderate temperature and medium light intensity. However, F-v/F-m dropped obviously with no change in MDA contents, and photoinhibition appeared in indica rice cv. 'Shanyou 63' under medium temperature and strong light intensity. Furthermore, both photoinhibition and photooxidation were observed in two rice cultivars under chilling temperature and strong light intensity. Experiments with inhibitors under chilling temperature and strong light intensity showed that indica rice had a decrease in DI protein content and SOD activity, and the extent of inhibition of xanthophyll. cycle and nonphotochemical quenching (qN) was larger, and a higher level of MDA was observed. The photoinhibition and photooxidation in indica rice were more distinct as compared with japonica rice. The authors suggested that PS II light energy conversion efficiency (F-v/F-m) and membrane lipid peroxidation were the key indices for the detection of photooxidation.
基金Project supported by the Basic and Applied Basic Research Project,Guangzhou Basic Research Plan(Grant No.202201011444).
文摘Understanding the photon number statistics of a quantum emitter(QE)interacting with complex photonic environments is fundamental to advances in quantum optics and nanophotonics.We introduce a general theoretical framework for calculating the modal photon number density spectrum(MPNDS)in arbitrary dielectric structures with an embedded two-level QE.We validate our approach by investigating a system composed of a two-level QE and a photonic crystal(PhC)slab with an L3 cavity and a waveguide,finding that the MPNDS exhibits significant changes in both waveguide and background radiative channels as the interaction between the QE and modal field transitions from weak coupling to strong coupling.We observe that the number of photons guided along the waveguide shows a strong dependence on the QE’s transition frequency and transition dipole moment,but demonstrates robustness to the transition dipole moment when the transition frequency approaches the waveguide cutoff frequency.Our work allows for the determination and tailoring of light emission characteristics across diverse radiative channels in complex photonic environments.
基金supported by the National Natural Science Foundation of China(No.31370702)the Key Project of Natural Science Foundation of Shandong Province(No.ZR2015JL014)+2 种基金the Key Research and Development Project of Shandong Province(No.2015GNC111022)Science and Technology Plan of Universities in Shandong Province(No.J13LC03)Natural Science Foundation of Shandong Province(No.ZR2015CL044)
文摘Soil moisture is a major limiting factor for plant growth on shell ridge islands in the Yellow River Delta. However, it is difficult to carry out situ experiment to study dominant plant photosynthesis physiological on the shell ridge islands under extreme soil water stress. To evaluate the adaptability of plants to light and moisture variations under extreme soil moisture conditions present on these islands, we measured photosynthetic gas exchange process, chlorophyll fluorescence, and stem sap flow variables for 3-year-old trees of Tamarix chinensis Lour, a restoration species on these islands, subjected to three types of soil water levels： waterlogging stress （WS）, alternating dry-wet （WD）, and severe drought stress （SS） to inform decisions on its planting and management on shell ridge islands. Gas exchange, chlorophyll fluorescence, and stem sap flow in T. chinensis were then measured. Net photosynthetic rate （PN）, transpiration rate （E）, and water use efficiency （WUE） were similar under WS and alternating dry-wet conditions, but their mean E and WUE differed significantly （P 〈 0.05）. Under SS, the PN, E and WErE of T. chinensis leaves varied slightly, and mean PN, E and WUE were all low. Apparent quantum efficiency （AQY）, light compensation point （LCP）, light saturation point （LSP）, and maximum net photosynthetic rate （PNmax） of leaves were not significantly different （P 〉 0.05） under WS and dry-wet conditions; however, under extreme drought stress, compared with the dry-wet conditions, LCP was higher, Lsp was lower, and AQy and PNmax were both at the lowest level. Therefore, drought stress weakened light adaptability of leaves, and the efficiency of light transformation was poorer. （3） Maximum photochemical efficiency （Fv/Fm） and the actual photochemical efficiency （ΦPSII） were similar under waterlogged stress and dry-wet conditions, indicating a similar healthy photosynthetic apparatus and photosynthetic reaction cen- ter activity, respectively. Under SS, Fv/Fm was 0.631, and the coefficient of non-photochemical quenching （NpQ） was 0.814, which indicated that while the photosynthetic mechanism was damaged, the absorbed light energy was mainly dissipated in the form of heat, and the potential photosynthetic productivity was significantly reduced. The daily cumulants of sap flow of T. chinensis under drywet alternation and severe drought stress were. 22.25 and 63.97% higher, respectively, than under waterlogging stress. Daily changes in sap flow velocity for T. chinensis differed under the three soil water levels. Stem sap flow was weak at night under severe drought stress. Under drywet alternation, daytime average stem sap flow velocity was the highest, and night stem flow accounted for 10.26% of the day cumulants, while under waterlogged stress, the average nightly stem flow velocity was the highest, accounting for 31.82% of the day cumulants. These results provide important information for regional vegetation restoration and ecological reconstruction.
基金funded by the National Natural Science Foundation of China (Grant Nos. 52161145404, 61905236, 51961145110)the Fundamental Research Funds for the Central Universities (Grant No. WK2100230020)USTC Research Funds of the Double First-Class Initiative (Grant No. YD3480002002)
文摘In this work,we design and fabricate a deep ultraviolet(DUV)light-emitting array consisting of 10×10 micro-LEDs(μ-LEDs)with each device having 20μm in diameter.Strikingly,the array demonstrates a significant enhancement of total light output power by nearly 52%at the injection current of 100 mA,in comparison to a conventional large LED chip whose emitting area is the same as the array.A much higher(~22%)peak external quantum efficiency,as well as a smaller efficiency droop forμ-LED array,was also achieved.The numerical calculation reveals that the performance boost can be attributed to the higher light extraction efficiency at the edge of eachμ-LED.Additionally,the far-field pattern measurement shows that theμ-LED array possesses a better forward directionality of emission.These findings shed light on the enhancement of the DUV LEDs performance and provide new insights in controlling the light behavior of theμ-LEDs.
基金Funded by Key Laboratory of Ministry of Education for Conveyance and Equipment,East China Jiaotong University(No. 09JD09)
文摘Counter beam lighting was introduced as well as transverse symmetrical lighting and longitudinal symmetrical lighting.Simulation experiments were carried out by using DIAlux lighting software for the above three lighting methods.The results show that counter beam lighting is more reasonable to be adopted in the tunnel entrance zone because its threshold increment of disability glare is greater.Counter beam lighting can improve the background luminance of the obstacles and lighting efficiency compared with transverse symmetrical lighting and longitudinal symmetrical lighting.Therefore,tunnel lighting energy-saving can be achieved by reducing the road luminance demands and luminaries power.Longitudinal symmetrical lighting is conducive to the large luminaries spacing in the tunnel internal zone;so power consumption can be reduced by decreasing the number of luminaries used.Tunnel walls are unsuitable to pave with smooth or bright material.Installation height of the luminaries has less effect on counter beam lighting.
基金supported by Startup Funds from the Central Organization Department and the South China University of Technology(SCUT),as well as funds from the national natural science foundation of China(Grant No:U2001217)the Guangdong Science and Technology Program(2020B121201003,2019ZT08L075,2019QN01L118,2021A1515012545)the Fundamental Research Fund for the Central Universities,SCUT(2020ZYGXZR095).
文摘ABSTRACT Embedding submicrocavities is an effective approach to improve the light out-coupling efficiency(LOCE)for planar perovskite light-emitting diodes(PeLEDs).In this work,we employ phenethylammonium iodide(PEAI)to trigger the Ostwald ripening for the downward recrystallization of perovskite,resulting in spontaneous formation of buried submicrocavities as light output coupler.The simulation suggests the buried submicrocavities can improve the LOCE from 26.8 to 36.2%for near-infrared light.Therefore,PeLED yields peak external quantum efficiency(EQE)increasing from 17.3%at current density of 114 mA cm^(−2)to 25.5%at current density of 109 mA cm^(−2)and a radiance increasing from 109 to 487 W sr^(−1)m^(−2)with low rolling-off.The turn-on voltage decreased from 1.25 to 1.15 V at 0.1 W sr^(−1)m^(−2).Besides,downward recrystallization process slightly reduces the trap density from 8.90×10^(15)to 7.27×10^(15)cm^(−3).This work provides a self-assembly method to integrate buried output coupler for boosting the performance of PeLEDs.
文摘Available light under forest canopies includes two components, diffuse light and direct light (sunflecks), and is characterized as low and highly dynamic. Understory habitats under different forest types experience different light conditions. Sunflecks as a critical resource for understory plants have great importance on carbon gain of understory plants. Under the light-limiting habitat, understory plants exhibit a high light utilization efficiency attributed by a post-illumination CO2 uptake. Although different species have different photosynthetic responses, shade plants appear to be acclimated to respond more quickly and efficiently to sunflecks. This acclimation includes a faster induction, relatively lower rate of induction loss, lower photosynthetic compensation point, and higher water use efficiency. The process that shade plants harvest light energy is not well known. Studies of photosynthetic responses to sunflecks in natural conditions are rare. Little is known about constraints on sunfleck utilization, which may change seasonally. Extensive field studies in conjunction with laboratory investigations will be needed to further understand potential and actual constraints on sunfleck utilization. Most studies on photosynthetic responses to fluctuating light condition were done in the level of leaves. Fluctuating light utilization on the basis of whole plants and populations presents future challenges to ecologists.
基金National Natural Science Foundation of China(No.61071087)Reward Fund of Outstanding Youth and Middle Age Scientist of Shandong Province(No.BS2009N5002)
文摘Because of its very low light extraction efficiency(LEE),LED is limited to be widely used under the condition of the internal quantum efficiency which up to 90%.In order to fullfill the design of a more efficient GaN-based blue light LED,the model including deeply etched surface photonic crystals(PhCs)LED is discussed using mode analysis method from light waveguide theory.The distributions of all order modes in GaN layer are obtained by the effective index approximation.The light extraction efficiencies are also calculated by finite-difference time-domain method(FDTD).The emulated results fully coincide with the former analysis.Because the manufacture of the surface photonic crystal is feasible,the work can be very meaningful to design and manufacture the high efficiency GaN-based blue light LED in factory for a large amount.
文摘Currently, daylighting ducts system is widely used as a daylighting device. Generally, daylighting duct system efficiently takes light from outside during the day, and conveys daylight to required location through light duct manufactured by high reflectance mirror. Daylighting duct system can convey daylight to underground space that has no windows opening to external space. Daylighting system is composed of light collection part, light guide part and light emission part. Efficiency of daylighting system is depending on type of each part used in the system. However, it is very difficult to estimate exact light flow in the system considering type of the parts. Authors performed measurement experiments to make clear the light flow with real-size model and miniature model of daylighting duct system. We discussed effect of type of the parts on efficiency of daylighting duct system.
基金Supported by the National Natural Science Foundation of China under Grant No 91441201
文摘Highly efficient and stable hybrid white organic light-emitting diodes （HWOLEDs） with a mixed bipolar interlayer between fluorescent blue and phosphorescent yellow emitting layers are demonstrated. The bipolar interlayer is a mixture of p-type diphenyl （l0-phenyl-lOH-spiro [acridine-9,9＇-fluoren]-3Lyl） phosphine oxide and n-type 2＇,2- （1,3,5-benzinetriyl）-tris（1-phenyl-l-H-benzimidazole）. The electroluminance and Commission Internationale de l＇Eclairage （CIE1931） coordinates＇ characteristics can be modulated easily by adjusting the ratio of the hole- predominated material to the electron-predominated material in the interlayer. The hybrid WOLED with a p-type：n-type ratio of 1：3 shows a maximum current efficiency and power efficiency of 61.1 ed/A and 55.8 lm/W, respectively, with warm white CIE coordinates of （0.34, 0.43）. The excellent efficiency and adaptive CIE coordi- nates are attributed to the mixed interlayer with improved charge carrier balance, optimized exciton distribution, and enhanced harvesting of singlet and triplet excitons.
基金This work was supported by National Key R&D Program of China(2022YFB3605103)the National Natural Science Foundation of China(62204241,U22A2084,62121005,and 61827813)+3 种基金the Natural Science Foundation of Jilin Province(20230101345JC,20230101360JC,and 20230101107JC)the Youth Innovation Promotion Association of CAS(2023223)the Young Elite Scientist Sponsorship Program By CAST(YESS20200182)the CAS Talents Program(E30122E4M0).
文摘240 nm AlGaN-based micro-LEDs with different sizes are designed and fabricated.Then,the external quantum efficiency(EQE)and light extraction efficiency(LEE)are systematically investigated by comparing size and edge effects.Here,it is revealed that the peak optical output power increases by 81.83%with the size shrinking from 50.0 to 25.0μm.Thereinto,the LEE increases by 26.21%and the LEE enhancement mainly comes from the sidewall light extraction.Most notably,transversemagnetic(TM)mode light intensifies faster as the size shrinks due to the tilted mesa side-wall and Al reflector design.However,when it turns to 12.5μm sized micro-LEDs,the output power is lower than 25.0μm sized ones.The underlying mechanism is that even though protected by SiO2 passivation,the edge effect which leads to current leakage and Shockley-Read-Hall(SRH)recombination deteriorates rapidly with the size further shrinking.Moreover,the ratio of the p-contact area to mesa area is much lower,which deteriorates the p-type current spreading at the mesa edge.These findings show a role of thumb for the design of high efficiency micro-LEDs with wavelength below 250 nm,which will pave the way for wide applications of deep ultraviolet(DUV)micro-LEDs.
基金financially supported from the National Natural Science Foundation of China(5220235)academic funding supported by Soochow University(NH10900123)+1 种基金the Gusu Innovation and Entrepreneurship Leading Talents Program(ZXL2023184)the Natural Science Foundation of Jiangsu Higher Education Institutions of China(22KJB150033)。
文摘Semitransparent organic solar cells(ST-OSCs)have garnered considerable attention as promising renewable energy technology for integrating photovoltaics into buildings.However,there is a trade-off between power conversion efficiency(PCE)and average visible transmittance(AVT),which hinders the achievement of a high light utilization efficiency(LUE).In this study,we propose a valuable method to address this challenge by replacing the transparent top electrode,Ag,with a 20 nm layer of Au.The ST-OSCs based on the 20 nm Au electrode demonstrate superior exciton extraction,more efficient charge collection,and higher color-rendering index(CRI)due to their smoother surface,higher conductivity,and enhanced visible light transmittance,resulting in a significantly higher PCE of 13.67%and an enhanced AVT of 30.17%,contributing to a high LUE of 4.15%.Additionally,optically transparent dielectric layers,applied on the front and back sides of the ST-OSCs to further boost performance,delivered an impressive LUE of 4.93%,with PCE and AVT values reaching 14.44%and 34.12%,respectively.Notably,the champion ST-OSCs also exhibited a favorable CRI value of 93.37.These achievements represent the bestperforming ST-OSCs to date with both high LUE and CRI and hold significant implications for the prospective commercialization of ST-OSCs.
文摘In this paper, a new illumination system with ultra high performance (UHP) lamp is proposed for projection display. Parabolic reflector (PR) and compound parabolic retro-reflector (CPR) were jointly used to collect and collimate the light generated from UHP lamp. A polarization converter system (PCS) was used to increase the light efficiency of the projection display system. A beam transformer between PCS and 2f imaging systems was directly used to make the illumination meet the requirement of projection display system. With the consideration of the loss of reflection, the light efficiency in this projection display system was estimated to be 15.6%.
