最新刊期
卷 41 ， 期 3 ， 2020
- 摘要：Flexible information displays have the promising potential for the future optoelectronic application. However, achieving the highly efficient and stable flexible light-emitting diodes (LEDs) is still a big challenge due to the limited choices of electrode materials and flexible substrates. Herein, the flexible perovskite light-emitting diodes (Pe-LEDs) by combining the flexible substrate based on a photopolymer with the CsPbBr3 quantum dots (QDs) emitting layer were fabricated. In order to improve electrons injection and transport, Ag was used as the cathode. As a result, the green light emitting Pe-LEDs with high luminance of 10 325 cd·m-2 and high color purity with the full-width-at-half-maximum (FWHM) of 19 nm were obtained. In addition, the Pe-LEDs exhibit good flexibility and mechanical ductility, and the as-prepared flexible device still maintains its optoelectronic performance even after repeated bending 100 cycles under a bending angle of about 180°. The research presents a further step toward the future application of flexible displays.关键词：CsPbBr3 QDs;photopolymer;Ag electrode;flexible light-emitting diode278|208|0更新时间：2020-08-12
- 摘要：Aluminate glass composition is (100-x)(23.6Al2O3-53CaO-7.7BaO-2.1Na2O-10.3Ga2O3-3.1B2O-0.02Er2O3)-xYb2O3(x=0, 0.9, 1.9, 2.8, 3.6, 4.5), and it was prepared by conventional melting and quenching method. The effects of Yb2O3 content on the physical properties, thermal stability, spectral properties and structure of Yb3+/Er3+ co-doped aluminate glasses were systematically investigated by using differential scanning calorimetry (DSC), absorption spectrum, fluorescence spectrum, infrared spectrum and Raman spectra. The results show that the density and refractive index increased with the increasing content of Yb2O3. Increasing Yb2O3 content is beneficial to increase the absorption intensity of the Yb3+/Er3+ doped aluminate glass at 976 nm. DSC test indicates that resistance to crystallization of Yb3+/Er3+ co-doped aluminate glasses increases with the addition of Yb3+ ion content. The up-conversion emission at 527, 549, 666 nm corresponding to the 2H11/2→4I15/2, 4S3/2→4I15/2 and 4F9/2→4I15/2 transitions of Er3+ ions, the red to green luminescence intensity ratio and near-infrared fluorescence intensity at 1.53 μm corresponding to 4I13/2→4I15/2 are significantly enhanced as Yb2O3 content increasing. When Yb2O3 content reached 3.6%, the glass has the strongest near-infrared fluorescence intensity at 1.53 μm. Meanwhile, the forward energy transfer efficiency η1 of Yb3+→Er3+ is the maximum, about 82.9%. In this Yb/Er co-doped aluminum glass, the maximum emission cross section, the full width at half maximum (FWHM) of the fluorescence of 1.53 μm and maximum fluorescence lifetime of Er3+ are 0.77×10-20 cm2, 39.4 nm and 4.46 ms, respectively.关键词：aluminate glass;Yb3+/Er3+ co-doping;up-conversion emission;1.53 μm emission163|118|0更新时间：2020-08-12
- 摘要：Two-dimensional nano-array structures have been widely used in many optoelectronic devices due to their excellent optical performances. In this work, nano-pillar arrays were fabricated on GaAs substrate by self-assembled monolayer SiO2 nanospheres etching. Monolayer SiO2 nanospheres were self-assembled on GaAs substrate by rotary coating. The order of the nanosphere distribution was improved by improving the oxygen plasma hydrophilic treatment process of GaAs surface, and a large area of tightly arranged monolayer nanosphere was obtained under the power ratio of 100 W+80 W, the chamber pressure of 4 Pa, the oxygen flow rate of 20 mL/min and the etching time of 1 200 s. Taken this monolayer nanosphere as the etching mask, highly ordered GaAs nano-pillar array was then fabricated by inductively coupled plasma etching. The reflectivity of the GaAs nano-pillar array structure was found to be about 5% in a specific band by spectral analysis, which shows that light absorption can be enhanced effectively and can further match the requirements of actual optoelectronic devices.关键词：SiO2 nanospheres;oxygen plasma;ICP etch155|71|0更新时间：2020-08-12
- 摘要：NaGd(WO4)2 (NGW):Yb3+,Ho3+,Cr3+ micro-crystals were synthesized through a hydrothermal method. The effects of Cr3+ doping concentrations on the crystal structure, micro-morphology, upconversion luminescence and temperature sensing properties of the samples were investigated. Under the excitation of 980 nm laser, all of the samples show weak green (centred at 546 nm) and strong red (660 nm) emissions, which corresponding to the energy transition of 5F4, 5S2→5I8 and 5F5→5I8 of Ho3+, respectively. With the increase of Cr3+ contents, the intensity of green emission decreases gradually, while the red emission increases firstly and then decreases, reaching the maximum at 10%, and the color coordinates of the samples shift gradually towards the red region. The spectra of temperature dependence of luminescence indicate that NGW:Yb3+,Ho3+,10% Cr3+ micro-crystals exhibit excellent temperature characteristic, and the sensitivity reaches the maximum at 486 K with the value of 0.033 7 K-1, which is nearly doubled compared with that of NGW:Yb3+,Ho3+ micro-crystals.关键词：tungstate;hydrothermal method;up-conversion;temperature sensing186|123|1更新时间：2020-08-12
- 摘要：The phosphors CaLuBO4:xTb3+ were synthesized through the solid-state reaction technique. The structure, photoluminescence properties of these phosphors were described. Upon excitation with UV light excitation, the photoluminescence emission spectra could be assigned to the transitions of Tb3+ from 5D3→7FJ (J=6, 5, 4) and 5D4→7FJ' (J'=6, 5, 4, 3). The two strong emissions peaked at 545 nm and 554 nm, which arose from the 5D4-7F5 of Tb3+, respectively. The photoluminescence excitation spectra show a broad 4f-5d band and f-f transitions in UV region. The dependence of photoluminescence intensities on Tb3+ concentration was studied. The luminescence lifetimes of 5D3 and 5D4 energy level were measured and analysed, respectively. The CaLuBO4:xTb3+ phosphor is a novel yellow-green emitting phosphor suitable for ultraviolet light excitation.关键词：phosphor;photoluminescence;fluorescence lifetime212|171|2更新时间：2020-08-12
- 摘要：Li+/La3+ co-doped Li0.06La0.06Ba0.84Si2O5:4% Eu2+ (LLBSO:Eu2+) green-emitting phosphors were prepared through a high-temperature solid state reaction. Compared with undoped Ba0.96Si2O5:4% Eu2+ (BSO:Eu2+) sample, it can be found that Li+/La3+ co-doping is an efficient strategy for synthesizing single-phased LLBSO:Eu2+ at lower temperature in less synthesis time. Our results indicate that this strategy can lead to not only the reduced cost but also the improved optical performances. The related tests suggest that, for Li+/La3+ co-doped BSO:Eu2+ phosphors, the particle size is in the range of 1.1-2.7 μm and no obvious aggregation can be found, suggesting that it meets the requirements for coating LED chips. Upon near-ultraviolet LED chip (365 nm) excitation, LLBSO:Eu2+ exhibits a strong broadband emission around 502 nm, which is attributed to the 5d-4f transition of Eu2+. Its luminescent intensity reaches 168% as strong as that of the undoped sample. Furthermore, for LLBSO:Eu2+ phosphor, the luminescent intensity measured at 150℃ is~98% as strong as that measured at room temperature, suggesting it has good thermal stability. The CIE coordinate of LLBSO:Eu2+ phosphors is (0.217, 0.410), which locates in the green light region. White LEDs with different color temperatures ranging from 2 918 K to 4 037 K, were fabricated using blend strategies. These LEDs exhibit high color rendering index (Ra>85) and good thermal stability. Our studies suggest that LLBSO:Eu2+ green-emitting phosphor is one kind of candidates for fabricating near-ultraviolet excited white LEDs.关键词：rare earth;phosphor;photoluminescence;white LED185|110|2更新时间：2020-08-12
- 摘要：To obtain high-quality β-Ga2O3 thin film, GaN thin film grown on c-plane sapphire is made into Ga2O3/GaN/sapphire template by thermal oxidation, and the β-Ga2O3 thin film is grown on the template by metal-organic chemical vapor deposition(MOCVD). The crystal structure and surface morphology of the samples are measured and analyzed by X-ray diffraction, atomic force microscope and field emission scanning electron microscope. The results show that the crystal quality of the β-Ga2O3 films is affected by GaN film oxidation effect and MOCVD process conditions greatly. By optimizing the experimental conditions, the high-quality β-Ga2O3 thin films are obtained. By comparing with the films grown on sapphire or GaN films, the crystal quality of the β-Ga2O3 films is found improved obviously. We find that this method successfully transforms the heteroepitaxy of the β-Ga2O3 film on sapphire substrate or GaN/sapphire template into the homoepitaxy of that on Ga2O3/GaN/sapphire template, effectively reduces the large lattice mismatch and thermal mismatch between β-Ga2O3 film, sapphire and GaN, and is beneficial to improve the crystal quality of β-Ga2O3 film.关键词：gallium oxide;high temperature oxidation;metal-organic chemical vapor deposition210|74|1更新时间：2020-08-12
- 摘要：Dye sensitizers are the key photoelectric conversion materials in dye-sensitized solar cells (DSSCs). The electrons in sensitizers transfer from the low level of ground state to the high level of excited state and generate effective potential difference when sensitizers are excited by light. Designing and screening sensitizer with excellent properties is beneficial to promote their photoelectric conversion efficiency. A series of tetrathiafulvalene (TTF)-based metal-free dye sensitizers with different π-bridge were designed based on the relevant experimental study, and their photoelectric conversion and the intramolecular electron transfer characteristics were systematically investigated by using density functional theory (DFT) and time-dependent DFT. Results show that the overall performance of TTF-based metal-free dye sensitizer with cyclopentathiophene and its derivatives as π-bridge was significantly improved in terms of the better charge separation state, broadened spectral absorption coverage rage, improved light-harvesting efficiency and enhanced intramolecular electron transfer performance.关键词：tetrathiafulvalene-based metal-free dye sensitizers;density functional theory;photoelectric conversion;intramolecular electron transfer169|423|0更新时间：2020-08-12
- 摘要：Research on advanced methods of graphene nano-trimming is very important for graphene-based electronic and optical devices. In this paper, the inverse opal structure is fabricated by the template method, and the inverse opal nanonet structure is used to perform nano-cutting of graphene by photocatalytic reduction of graphene oxide. Scanning electron microscopy and infrared spectroscopy characterization are applied to study the electrical properties of graphene after cutting. Experiments show that the reaction time and the size of the colloidal particles will affect the period and neck width of the graphene oxide after cutting, thereby affecting the electrical properties of the graphene oxide after reduction. It is a feasible method to use nano-network structure to cut graphene nano-cuts. The properties of the cuts can be controlled by controlling the template size and reaction conditions.关键词：graphene;inverse-opal structures;photocatalytic method152|408|0更新时间：2020-08-12
Synthesis and Properties of Materials
- 摘要：Employing graphene oxide as a saturable absorber, we experimentally demonstrated a passively Q-switched mode-locked (QML) operation of a Tm,Ho:CaYAlO4 bulk laser. In this case, the absorbed threshold power of Tm,Ho:CaYAlO4 bulk laser was measured as 293 mW by using a 3% output coupler. When the absorption pumping power reached 1 859 mW, it entered a stable Q-switched mode-locked operation state. And when the pumping power reached 3 W, the corresponding maximum output power is 213 mW, corresponding to a slope efficiency of 10.1%, the central wavelength of 2 089 nm, the repetition frequency of 100 MHz, and the modulation depth being close to 100%.关键词：Tm;Ho:CaYAlO4 laser;passively Q-switched mode-locked;graphene oxide;saturable absorber143|252|4更新时间：2020-08-12
- 摘要：Four chip-scale packaged light-emitting diode (CSP-LED) modules with different pitches were mounted on an aluminum substrate. The EL spectrum, lumen efficiency, luminous flux, correlated color temperature and other photoelectric parameters of CSP-LED modules with different patch pitches are measured. The results show that under low current (20~400 mA), with the increase of the injection current, the photoelectric properties of blue and white light samples with different arrangement intervals basically show the same change law. It is like that the luminous flux and optical power increase linearly, and the optical efficiency is basically stable. Under high current (1~1.5 A), as the arrangement spacing between chips decreases, the integrated intensity of the EL spectrum decreases, the color temperature increases, the red ratio decreases, and the luminous flux with an arrangement spacing of 0.2 mm attenuated by 84.58%. In contrast, the attenuation of luminous flux at 3 mm and 5 mm arrangement spacing is significantly slowed down, 8.96% and 3.58%, respectively. These phenomena are related to factors such as the forbidden band width, thermal stress, and non-radiative recombination. The results show that the main reason for the attenuation of CSP white LED light flux is the degradation of phosphors. Considering the actual production cost, when the spacing is 3 mm, it is conducive to heat dissipation, thereby improving the LED photoelectric performance characteristics and its own service life.关键词：chip-scale packaged(CSP);light-emitting diode(LED);thermal congestion;layout structure168|200|3更新时间：2020-08-12
- 摘要：Organic phototransistor(OPT) is made by introducing a light-controlled ‘gate’ into the structure of an organic field-effect transistor(OFET), which is a new type of photodetector. The performance parameters of OPTs, including photosensitivity(P) and photoresponsivity(R), are closely related to the contact between source/drain electrodes and the active layer. In this paper, a single layer of pentacene and CuPc based OPT with Au and Al electrodes were prepared by vacuum evaporation respectively. Their output and transfer characteristics in dark and under illumination were studied. The results showed that Au electrodes were more suitable for high mobility pentacene active layer with better contact characteristics. The pentacene-based OPT with Au electrodes gained the same level of P as that with Al electrodes at around 3×104, but the R of the former was 13 times higher than that of the latter. While for low mobility CuPc-based OPT, Schottky contact was formed between the Al electrode and the active layer, which was beneficial for suppressing dark current, enhancing exciton dissociation efficiency and improving photocurrent. Furthermore, the CuPc-based OPT with Al electrode obtained the same order of magnitude R as the device with Au electrode, but the P of the former was 102 times higher than the latter. The energy band variations of the electrodes/active layer Schottky contacts under illumination were discussed in this paper. And the preliminary screening rules of the electrode materials and active layer materials for OPTs were summarized.关键词：organic phototransistor;photosensitivity;photoresponsivity;Schottky contact151|484|0更新时间：2020-08-12
- 摘要：For the comparative study of the reliability of the low color temperature light source made by phosphor-free LEDs and conventional phosphor-converted LEDs, 85℃ accelerated aging and temperature step-stress tests were carried out. The variation of each photoelectric parameters during the aging process was recorded, and the aging mechanism of the two different kinds light sources was analyzed. The results show that both types of light sources exhibit good stability under the accelerated aging at 85℃ with a current density of 20 A/cm2. However, as the current density increases, more obvious attenuation of luminous flux appears in phosphor-converted light sources. As the temperature increases, the phosphor-free light source still shows good stability up to about 200℃. However, the phosphor-converted light sources exhibit significant luminous flux attenuation and color temperature increase after 175℃. These results indicate that the phosphor-free light source shows excellent reliability when current stress or temperature stress increases.关键词：low color temperature;phosphor-free;LED light source;reliability;aging192|249|3更新时间：2020-08-12
Device Fabrication and Physics
- 摘要：Green fluorescent castor carbon quantum dots(CO-CQDs) with excellent fluorescence properties were synthesized by one-step hydrothermal method with natural biomass peeled castor. By combining the as-synthesized CO-CQDs with eosin Y(EY), a novel ratiometric fluorescence probe CO-CQDs/EY was formed. In the Na2HPO4-citric acid buffer solution of pH=4.00, under the excitation wavelength of 320 nm, the CO-CQDs/EY complex showed two independent fluorescence emission peaks at 405 nm and 540 nm. The fluorescence signals of 405 nm and 540 nm could be both quenched by Cr(Ⅵ). In the presence of L-ascorbic acid, the fluorescence signal at 540 nm was significantly increased, while the fluorescence intensity at 405 nm still remained unchanged. Therefore, a novel method for L-ascorbic acid analysis was developed based on this fluorescence ratiometric probe CO-CQDs/EY. This ratiometric method showed excellent specificity, sensitivity and accuracy. The optimum conditions of experiment were investigated and the mechanism of interaction was discussed. Under the optimized experimental conditions, the linear range of this method was 5.0×10-8-4.0×10-6 mol/L, and the detection limit was calculated to be 3.7×10-8 mol/L. Moreover, this method has been successfully applied to L-ascorbic acid analysis in drugs, vegetables and fruits, showing great potential in real sample analysis.关键词：carbon quantum dots;eosin Y;Cr(Ⅵ);ratiometric fluorescence probe;L-ascorbic acid211|402|3更新时间：2020-08-12
- 摘要：Aiming at the present situation of the uneven agricultural product quality which is caused by the poor illuminance uniformity and the poor mixed color uniformity in plant growing shelf adopted by existing plant factory plant cultivation, we put forward a kind of design scheme of plant growing shelf with high light mixed evenness and high color mixed uniformity. Different from the design scheme whose light source is above the planting plane, red and blue LEDs were arranged at regular intervasl installed in the boss club of planting plane, and a diffuse surface was designed on the top of the plant growing shelf. The import of the reflection surface plays the role of increasing mixed light distance, improves the ray coupling degree, so as to achieve high light mixed uniformity and high color mixed uniformity. Photosynthetic photon flux density uniformity and color mixed uniformity were further introduced as examining index. The Taguchi method was used to design and conduct experimental exploration to study the influence of different levels of factors on the uniformity of light source in plant planting area, and ANOVA theory was used to analyze the influence degree of each factor on the quality. After multiple optimizations, we finally obtained the best system design scheme whose intensity of illumination uniformity is 94.58%, the color mixed uniformity is 90% and the energy utilization rate is 41.42%. Then, the effects of different light distribution curves on the uniformity of the culture frame were studied. Finally, by measuring the illuminance and spectral distribution of the plant surface at different heights, it is detected whether the growth of the plant will block the light. The results show that the plant lighting system can provide uniform illumination during the growth of the plant, and the occlusion problem is almost negligible.关键词：plant growing shelf;plant light source;optical design;light distribution curve;Taguchi197|176|2更新时间：2020-08-12
Luminescence Applications and Interdisciplinary Fields
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