最新刊期
卷 41 ， 期 8 ， 2020
- 摘要：Metal halide perovskite materials have great application potential in the next generation flat panel display and solid state lighting, due to their unique features such as low cost, high color saturation, high photoluminescence quantum yield, tunable emission and solution processing. Since the first observation of perovskite electroluminescence at room temperature in 2014, the external quantum efficiencies(EQEs) of green, red and near-infrared perovskite light-emitting diodes(PeLED) have rapidly exceeded 20% to date. Such rapid efficiency improvement can be ascribed to the continuous optimization of perovskite materials and device structures, as well as a deeper understanding of their luminescence mechanism. Compared with green, red and near-infrared PeLEDs, the development of blue PeLED is relatively slow, which seriously restricts the development of full-color PeLEDs. In the last year, the efficiency of blue PeLED has increased significantly, and the EQE has reached over 10%. In this review, we summarize the design and preparation of blue perovskite materials and the optimization strategies of device structure for high performance PeLEDs, and the development direction and problems of blue PeLED are discussed in the end.关键词：blue emission;perovskite;light-emitting diodes;material preparation;device optimization652|1096|5更新时间：2020-09-10
- 摘要：Ⅲ-Ⅴ compound semiconductors have wide band gap and high carrier mobility, making them suitable candidates for light-emitting diodes(LEDs), laser diodes(LDs), high electron mobility transistors(HEMTs) and other optoelectronics. For covalent epitaxy of Ⅲ-Ⅴ compounds on hetero-substrates, high quality epilayer can only be obtained when the lattice mismatch between the substrate and epilayer is negligible. However, van der Waals epitaxy(vdWE) has been proven to be a useful route to relax the requirements of lattice mismatch and thermal mismatch between the epilayer and the substrate. By using vdWE, the stress in epilayer can be sufficiently relaxed, and the epilayer can be easily exfoliated and transferred, which is useful for the Ⅲ-Ⅴ compound-based novel devices fabricating. In this paper, we reviewed and discussed the important progresses on the researches of nitrides vdWE. The potential applications of nitrides vdWE are also prospected.关键词：graphene;van der Waals epitaxy;Ⅲ-Ⅴ compound320|356|1更新时间：2020-09-10
- 摘要：Rare earth doped upconversion materials have been widely used in display, anti-counterfeiting and bio-imaging fields due to their high chemical stability and low biotoxicity. The host lattice and doped ions of the upconversion materials determined their luminescence intensity and colors. Photonic crystals(PCs) are periodically arranged structures of materials with different refractive index. The most notable feature of PCs is the existence of photonic band gap(PBG). Light with a wavelength within the PBG cannot pass through the PC and will be reflected back. Therefore, PCs have excellent ability to manipulate light. This paper reviewed the research progress about the luminescence manipulating of rare earth doped upconversion materials by one-dimensional, two-dimensional and three-dimensional PCs, and introduced the method of controlling the luminescence by adjusting the relative position of the PBG and the upconversion emission peaks. We mainly focused on the ability of three-dimensional PCs with inverse opal or opal structures to control upconversion luminescence. For inverse PCs, the use of upconversion materials or other materials to construct inverse opal PCs to control upconversion luminescence was discussed in detail. For opal PCs, three-dimensional PCs constructed by colloidal microspheres with different refractive index were introduced for the regulation of the upconversion luminescence. Finally, the development in the study about co-effect of plasmon resonance and PBG to enhance luminescence was summarized, and the future developing directions of upconversion luminescence regulation by PCs were prospected.关键词：upconversion;photonic crystals;photonic bandgap;luminescence regulation321|351|3更新时间：2020-09-10
- 摘要：In virtue of the high photoluminescence quantum yield(PLQY), tunable bandgap, facile synthesis, strong light-absorption ability and high defect tolerance, all inorganic perovskites CsPbX3(X=Cl, Br, I) hold a great promise in optoelectronic and photovoltaic fields, such as solid-state lighting, lasing, solar cell, and display etc. Despite the impressive achievements, the existing inorganic perovskites still receive strong criticism for the lack of thermal stability. This is because their poor thermal stability will observably reduce the durability, reliability, and long-term stability of optoelectronic devices. Herein, in this review, the influence of temperature on the stability of inorganic perovskites is discussed. The reasons behind the thermal decomposition of inorganic perovskites including the desorption of the surface ligands and phase transition under high temperatures are analyzed as well. Subsequently, the recent strategies towards enhancing the thermal stability of CsPbX3, such as ions doping, surface passivation, and composite structure, are emphatically reviewed. Furthermore, the performance parameters of optoelectronic perovskites-devices with high reliability reported so far are presented. Finally, we summarize and prospect the challenge and opportunity for future development of thermally stable inorganic perovskite CsPbX3.关键词：all inorganic perovskite;thermal stability;CsPbX3764|422|6更新时间：2020-09-10
Invited Review
- 摘要：Halide perovskite nano materials have received wide attention in recent years due to their excellent photoelectric properties. This paper reviews the highlight moment of perovskite quantum dots during the development from materials to multi-functional applications. We then discuss the current situation of the coexistence of opportunities and challenges in the process of rapid development, and emphasize the bottleneck of this field. It is hoped to promote the development of perovskite quantum dots.关键词：halide perovskite;quantum dots;multi-functional applications1064|1268|8更新时间：2020-09-10
40th Anniversary Special Column——Young Scientist on The Road
- 摘要：With an elaborate design, the silicate-based oxyfluoride glass ceramic with the composition of SiO2-Al2O3-Li2O-AlF3-LiF containing CsPbBr3 perovskite quantum dots was obtained by the re-heat treatment method. Impressively, controllable crystallization of the glass matrix and CsPbBr3 nanocrystal taking place in the glass ceramic were investigated by XRD. The microstructure characterizations of the CsPbBr3 nanocrystal were tested by TEM. The PL spectra, absorption spectra and CIE color coordinates were used to analyze the luminescence properties of CsPbBr3 quantum dots. As a result, the PL of the CsPbBr3 glass ceramic under optimum conditions shows robust green emission at 512 nm with narrow full width at half maximum(FWHM of 22.80 nm). The light emitting diode (LED) which was encapsulated by coupling the green-emitting CsPbBr3 glass ceramic with a 365 nm ultraviolet chip is expected to replace the traditional green phosphor as the key material in the field of new solid luminescent materials.关键词：CsPbBr3 perovskite quantum dots;glass ceramic;re-heat treatment;green LED303|296|1更新时间：2020-09-10
- 摘要：A two-steps sequential reaction with diaminouracil as precursor was implemented to produce two types carbon dots(CDs) with distinctive ligands. The structural information of ligands on CDs in each step was obtained by XPS and FT-IR. It revealed that the carbon dots(denoted as CDHB) directly produced in first stage beard uracil moiety with typical hydrogen bond donor -NH and acceptor -C[FY=, 1]O. CDHB displayed concentration dependent emission bathochromic shift. In addition, the dots' high affinity towards silver and mercury confirmed the presence of uracil receptor. In the second stage, it gradually converted to a form of dots with zwitterion symbol(denoted as CDZW). Under alkaline condition, uracil receptor converted to amine and carboxyl moieties in CDZW. The transformation of the receptor formed an aqueous solution of CDZW without any aggregate behavior. And no evident peak-shifted fluorescence was observed. When used as a fluorescent indicator, the CDZW displayed fluorescence turn-off upon the addition of nickel. Therefore, tailorable structures and binding properties of the two dots revealed the implement of one-pot sequential reactions, which provides a new access for controllable synthesis of carbon dots.关键词：carbon dots(CDs);aggregates;receptor;fluorescent indicator170|304|0更新时间：2020-09-10
- 摘要：The rutile-TiO2/ZnTiO3 composite photocatalysts were synthesized by a sol-gel method, and were heat treated at 650℃ for 1 h. The obtained samples were characterized by X-ray diffraction(XRD), scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and photoluminescence spectra(PL). The photocatalytic performance of samples was studied taking the degradation of methylene blue(MB) as the target reactant. The results show that the crystal structure of TiO2 is rutile phase and the grain size of TiO2 decreases with the increasing Zn/Ti molar ratio. ZnTiO3 forms when the Zn/Ti molar ratio reaches 2%. TiO2/ZnTiO3(Zn/Ti=8%) exhibits the highest photocatalytic activity, which can be attributed to the increase of surface hydroxyl content and the formation of TiO 2/ZnTiO3 semiconductor composite structure, accelerating the transfer of photogenerated electrons and holes. After 90 minutes of reaction, the degradation rate of MB by TiO2/ZnTiO3(Zn/Ti=8%) reaches 68.3% and the reaction rate constant k is 0.012 min-1, which are 1.85 times and 3 times higher than that of pure TiO2.关键词：rutile;ZnTiO3;photocatalytic performance;sol-gel164|136|1更新时间：2020-09-10
Synthesis and Properties of Materials
- 摘要：The current-voltage characteristics of an InGaAs/GaAs/InGaP quantum well laser at different temperatures have been investigated. A theoretical model has been developed to simulate the current-voltage characteristics of the laser. The length of the laser cavity utilized in the experiment is 0.3 mm, and the ridge width of the laser is 3 μm. Experimental voltage-temperature coefficients (dV/dT) of the laser are from 7.87 to 8.32 mV/K within 15-100 K, and are from 2.93 to 3.17 mV/K within 100-300 K. Theoretical voltage-temperature coefficients of the laser in the range of 15-100 K are 2.56 to 2.75 mV/K, and in the range of 100-300 K are 3.91 to 4.15 mV/K. Within 100-300 K, the theoretical voltage-temperature coefficients are close to the experimental coefficients. However, within 15-100 K, there are large differences between the theoretical coefficients and experimental ones, which need to be improved.关键词：quantum well laser;InGaAs/GaAs/InGaP;low temperature;voltage-temperature characteristics218|414|2更新时间：2020-09-10
- 摘要：V-cavity tunable semiconductor laser has great potential in optical network because of its advantages of simplicity, compactness and high performance. However, because the thermal conductivity of epitaxial structure is similar, most of the heat for wavelength tuning is lost directly, and so the tuning efficiency of laser is low. In this paper, a V-cavity laser with high tuning efficiency is designed by adding a heat insulation structure in the tuning region of the laser. Through the temperature model of V-cavity laser built by COMSOL Multiphysics, the effect of adding thermal insulation structure on the temperature of each part of the laser is analyzed. Through the optical field distribution established by Rsoft, the proper half wave coupler parameters are selected, so that the laser has the best mode selectivity.The results show that threshold gain difference between the lowest threshold mode and the next lowest threshold mode is 6.07 cm-1, and the tuning efficiency increases from 0.165 nm/mW to 0.3 nm/mW. Meanwhile, the addition of thermal insulation structure will not cause obvious temperature rise in other areas of the laser, and the negative impact on the device performance can be ignored.关键词：semiconductor lasers;wavelength tunable;thermal effects;thermal insulation196|576|1更新时间：2020-09-10
- 摘要：In this paper, we discuss the influence of different microcavity structures of the organic light-emitting devices(OLEDs) in order to improve the luminescence performance. We use the transfer matrix method to simulate and calculate the electroluminescence spectrum(EL)of the OLED, the microcavity organic light-emitting devices(MOLED) and the coupling microcavity organic light-emitting devices(CMC). And then we compare their EL characteristics. The structures of OLED, MOLED and CMC are glass/ITO(134 nm)/NPB(74 nm)/Alq3(62 nm)/Al, glass/DBR/ITO(134 nm)/NPB(74 nm)/Alq3(62 nm)/Al, and glass/DBR1/filler/DBR2/ITO(134 nm)/NPB(74 nm)/Alq3 (62 nm)/Al, respectively. The simulation results show that, the EL spectrum shape of the OLED has a broad spectrum band with the main peak at 561 nm and the shoulder peak at 495 nm, the MOLED has a narrow EL spectrum with single peak at 534 nm, the CMC has a twin narrow EL spectrum with the peaks at 520 nm and 556 nm respectively. The MOLED has the purest color. The integrated area of the OLED and the MOLED are basically the same. The CMC has the largest integrated area, which is 1.1 times of the former two devices. The simulation results show that CMC structure can be used to improve the luminescence efficiency and the color purity of the OLED.关键词：organic light emitting device;microcavity;coupled optical microcavity;spectrum simulation212|235|0更新时间：2020-09-10
Device Fabrication and Physics
- 摘要：The ground-state and excited-state energy and wave function of polaron in donor-center quantum dot with asymmetric Gaussian potential are derived by Lee-Low-Pines transformation and Pekar-type variational method, and then the two-level structure for a qubit is constructed. The measure of qubit decoherence time of quantum dots quantified by ground state decay time of two-state polaron is established, which is compared with the measure of qubit decoherence time of quantum dots quantified by polaron excited state decay time. And their physical mechanism is revealed. By studying the influence of dielectric constant ratio, electron-phonons coupling constant, temperature and electric field on the ground-state lifetime of bound polaron in the donor-center quantum dot with asymmetric Gaussian potential, the influence of material properties, temperature, electric field and other environmental factors on qubit decoherence of quantum dots is revealed.关键词：donor-center quantum dot;asymmetric Gaussian potential;bound polaron;ground-state lifetime178|205|0更新时间：2020-09-10
- 摘要：With resonance excitation and field ionization detection technology, the samarium atom odd-parity Rydberg states 4f66snp(J=1) near the first ionization limit were studied via the excitation path of the total angular momentum quantum number 0→1→0→1. Firstly, a total of 94 odd-parity Rydberg levels were found in the energy range of 45 200~45 500 cm-1. Secondly, 68 of these levels were assigned to three bound Rydberg series through the analysis of effective quantum number and structural characteristics of Rydberg energy levels, and energies of other 26 levels were given. Then, using the Rydberg-Ritz formula, the three series were fitted respectively, and the ionization limit of the samarium atom was (45 519.61±0.79) cm-1. Finally, six kinds of polarization combination were used to excite the samarium atom, and the polarization selection rule further verified that the total angular momentum quantum number of the Rydberg states was 1. The results confirm the applicability of the field ionization detection technology to the highly excited Rydberg states of the samarium atom. Meanwhile, ionization limit of the samarium atom obtained by fitting from the odd-parity Rydberg series is corresponded to the value (45 519.64±1.39) cm-1 obtained by fitting from the even-parity Rydberg series from the reference.关键词：samarium atom;odd-parity;Rydberg state;field ionization;polarization spectra200|134|0更新时间：2020-09-10
Theoretical Calculation and Spectral Analysis
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