锂漂移四象限硅光电二极管的原理和特性

在联合研制激光制导装置的过程中,我们小组承担了激光探测器的研制任务,经过两年多努力,试制成功锂漂移四象限硅光电二极管。与主机联调实验,实现了预期目标,各项技术参数均达到设计要求,取得了满意的效果。下面对它的原理和特性作一简单介绍。 1 基本原理固体受光照射后,它的光学性质可从麦克斯韦方程出发,用唯像理论加以讨论。

The Influence of Rapid Thermal Annealing on SiGe/Si Multiple-Quantum Wells p_-i_-n Photodiodes

The influence of thermal treatment on Si 1-x Ge x/Si multiple-quantum wells (MQW) p-i-n photodiodes has been investigated by photocurrent spectroscopy combined with X-ray double crystal diffraction.The cutoff wavelength is significantly reduced due to the Si-Ge interdiffusion and partial relaxation of the strained SiGe alloy.The values of the blue shift increase slowly with the annealing temperatures in the range of 750℃ to 850℃.However,the nonlinear changes in photocurrent intensities of the samples annealed at different temperatures have been observed,which is mainly dominated by the generation of misfit dislocations and the reduction of the point defects in the heating process.

High-Responsivity ZnS Schottky Barrier Photodiode Array for Ultraviolet Imaging

A different approach,using the molecular beam epitaxy (MBE)-grown ZnS-based Schottky photodiode technology,is applied to fabricate an 8×8 photodiode array.The micro-processing procedures of this photodiode array including standard photolithography,a number of metallisation,wet-chemical etching and SiO_2 deposition for insulation are developed.The detector is characterized to have a cutoff wavelength at 340 nm and the photo-responsivity measurements on the pixels result an ultraviolet (UV) response as high as 0.15 A/W,corresponding to an external quantum efficiency of 55% in the visible-blind spectral ranging from 400 down to 250nm.Imaging tests indicate that this array is able to capture the intensity profile of a given UV light source with reasonably good capability.

Optical Rectification Induced by Al-Si Schottky Barrier Potential and Mechanism of Two-Photon Response

By observing two-photon response and anisotropy of the light-induced voltage in Al-Si Schottky barrier potential,it is certified from the experimental and theoretical analysis that the built-in electric field generated by the Schottky barrier potential will induce the phenomena of optical rectification in Si photodiode.Thus,it is deduced that there must be double-frequency absorption caused by phase-mismatch in the mechanism of two-photon response of Si photodiode.If the intensity of the built-in electric field is strong enough,the double-frequency absorption will be the main factor of the two-photon response,which is different from the conventional opinion that the two-photon response is just the two-photon absorption.

Single Photon Detection of InGaAs/InP APD Based on Gated-mode Operation at Telecom Wavelengths

Based on the commercially available avalanche photodiodes, the basic needs of gated-mode operation for single photon are discussed. Gated-mode technique based on the experimental data for detection of single photon is analyzed at communication wavelengths so that the basic operation parameters can decide properly for efficient detection of single photon. The bias voltage has related to the punch-through voltage in combining the cooling technique with synchronization to decrease the dark counts.

Simulating Experiment and Circuit Simulation of RTD/HPT Photo-Controlled MOBILE

The MOBILE is a logic element realizing the monostable-bistable transition of a circuit that consists of two resonant tunneling transistors—the resonant tunneling diodes (RTDs) connected in series. It has several advantages including multiple inputs and multiple functions. In this paper, by connecting a heterojunction phototransistor (HPT) with the MOBILE, a novel optoelectronic functional device can be got, which presents the function of both photocurrent switching and photocurrent latching. These behaviors have been demonstrated for the first time by simulating experiments and circuit simulations, with RTDs firstly manufactured in China. Research indicates that the novel photo-controlled MOBILE has the same logic functions as conventional electrical MOBILE except for with light as an input signal.

Efficient Organic Multi-quantum Well Electroluminescent Devices Using Aluminum as Cathodes

Organic green light emitting devices(LEDs) with multi-quantum well(MQW) structure were fabricated. Aromatic diamine(TPD) was used as hole-transporting layer and potential barrier layer; Tris(8-hydroxyquinoline) aluminum(Alq 3) was acted as electron-transporting emitter and MQW green emitter. Air-stable aluminum(Al) was used as electron-injection contact. The influence of the thickness of potential barrier layer and the number of quantum well on the electroluminescent(EL) efficiencies of the devices was investigated. The organic LEDs with two quantum wells showed enhanced EL efficiencies. Maximum external quantum efficiency and brightness were 1.04 % and 7 000 cd/m 2, respectively.

Solar-Powered Direct-Current Loads in Small Buildings

Traditional light bulbs （e.g., incandescent, fluorescent） use too much electricity, convert very little energy into light of sufficient quality and in their production use toxic contaminants. During the last few years, a new type of light source, LED （light emitting diode） bulb, has gained increasing popularity and its costs are set to plunge even further. LED bulbs offer many advantages over traditional sources, and they can be used as a direct replacement to existing lighting. This paper will use a spreadsheet-based analysis with hourly solar data supplied by Ecotect to show that, the efficiency of LED installations can be increased when used in conjunction with photovoltaic modules, as the two generate （and use） DC （direct-current） electricity, thereby eliminating intermediate-level losses in the electronic circuitry. If a storage battery is included, the solar panels generate electricity during the times when the occupants are not necessarily using the lighting, but the stored electricity can be used to power the lighting when the energy is required. The latest results demonstrate that, a slight reduction in the required floor area to be lit allows the solar-battery-LED system to be implemented in small buildings using a storage battery size that is within the range of present commercial devices.

原地踏步以见证时间

刚在三月底,闭馆装修一时的澳大利亚当代艺术馆重新揭幕。重开后推出的首个展览,就是这个共有十一位艺术家参与的盛大国际展"Marking Time"。"Marking Time"一言本来意指原地踏步,然而这里的意思却表达出凝留时间的渴望。此词,对于现今的世界来说,可谓是前所未有地切身。古有先人说岁月如梭,现代有人说出既荒诞却又令人迷思的2012年大限之说。

Appending triphenyltriazine to 1,10-phenanthroline: a robust electron-transport material for stable organic light-emitting diodes

There has been an increasing demand for high-performance and cost-effective organic electron-transport materials for organic light-emitting diodes （OLEDs）. In this contribution, we present a simple compound 3-（3-（4,6-diphenyl-l,3,5-triazin-2-yl）phenyl）-1,10-phenanthroline through the facile Pd-catalyzed coupling of a triphenyltriazine boronic ester with 3-hromo-1,10-phenanthroline. It shows a high Tg of 112℃. The ultraviolet photoelectron spectroscopy measurements reveal a deep HOMO level of -6.5 eV. The LUMO level is derived as -3.0 eV, based on the optical bandgap. The low-temperature solid-state phosphorescent spectrum gives a triplet energy of -2.36eV. n-Doping with 8-hydroxyquinolatolithium （Liq, 1：1） leads to considerably improved electron mobility of 5.2 × 10 -6 -5.8 × 10 -5 cm2 v-1 S-1 at E=（2-5） × 10 5Vcm -1, in contrast with the triarylphosphine oxide- phenantroline molecular conjugate we reported previously. It has been shown that through optimizing the device structure and hence suppressing polaron-exciton annihilation, introducing this single Liq-doped electron-transport layer could offer high-efficiency and stable phosphorescent OLEDs.

Hybrid energy cell for simultaneously harvesting wind, solar, and chemical energies

We report a hybrid energy cell that can simultaneously or individually harvest wind, solar, and chemical energies to power some electronic devices. By utilizing the wind driven relative rotations between a polytetrafluoroethylene film and an etched A1 film attached on two acrylic tubes, the fabricated triboelectric nanogenerator （TENG） can deliver an open-circuit voltage of about 90 V, a short-circuit current density of about 0.5 mA/m2, and a maximum power density of 16 mW/m2, which is capable of directly lighting up 20 blue light- emitting-diodes （LEDs）. By integrating a TENG, a solar cell, and an electrochemical cell, a hybrid energy cell has been fabricated to simultaneously scavenge three different types of energies. As compared with the individual energy units, the hybrid energy cell exhibited much better performance in charging a capacitor. Moreover, we also demonstrated that the hybrid energies generated can be stored in a Li-ion battery for powering a commercial wind speed sensor and a temperature sensor. This work represents significant progress toward practical applications of hybrid energy cells, providing potential solutions for simul- taneously scavenging wind, solar, and chemical energies.

Lead-free perovskites: growth, properties, and applications

Lead halide perovskites have attracted extensive attention in recent years because of their excellent photoelectronic properties, such as high absorption coefficients,carrier mobilities, defect tolerances, and photoluminescence efficiencies. However, a key issue hindering their commercial application is the toxicity of lead. Replacing lead with other nontoxic elements is a promising solution to this problem.Considering their atomic radii, relative atomic masses, and electron arrangements, perovskites based on Sn, Bi, Sb, and other elements instead of Pb have been widely synthesized.Here, we summarized the growth methods, photoelectric properties, and device applications of these lead-free perovskites. First, we introduced several common growth methods for lead-free perovskites, including solution methods,solid-state reaction, and chemical vapor deposition methods.Second, we discussed the photoelectric properties and methods for optimizing these properties of lead-free perovskites with different structure dimensions. Finally, the applications of lead-free perovskites in solar cells, light-emitting diodes,and X-ray detectors were examined. This review also provides suggestions for future research on lead-free perovskites.

Wafer-scale arrayed p-n junctions based on few-layer epitaxial GaTe

Two-dimensional （2D） materials have attracted substantial attention in electronic and optoelectronic applications with the superior advantages of being flexible, transparent, and highly tunable. Gapless graphene exhibits ultra-broadband and fast photoresponse while the 2D semiconducting MoS2 and GaTe exhibit high sensitivity and tunable responsivity to visible light. However, the device yield and repeatability call for further improvement to achieve large-scale uniformity. Here, we report a layer-by-layer growth of wafer-scale GaTe with a high hole mobility of 28.4 cm^2/（V.s） by molecular beam epitaxy. The arrayed p-n ）unctions were developed by growing few-layer GaTe directly on fhree-inch Si wafers. The resultant diodes reveal good rectifying characteristics and a high photovoltaic external quantum efficiency up to 62% at 4.8 μW under zero bias. The photocurrent reaches saturation fast enough to capture a time constant of 22 μs and shows no sign of device degradation after 1.37 million cycles of operation. Most strikingly, such high performance has been achieved across the entire wafer, making the volume production of devices accessible. Finally, several photoimages were acquired by the GaTe/Si photodiodes with reasonable contrast and spatial resolution, demonstrating the potential of integrating the 2D materials with silicon technology for novel optoelectronic devices.

CH_2,NH,and O heteroatom substitution effects on the electronic,optical,and charge transport properties of a 2,1,3-benzothiadiazole-based derivative:Insights from theory

A set of CH2-,NH-,and O-substituted 2,1,3-benzothiadiazole(BTD)-based derivatives have been investigated theoretically in order to explore their electronic,optical,and charge transport properties.The calculation results show that the electronic and optical properties of the pristine molecule can be easily tuned through changing the S substituent in the central aromatic ring.Based on the calculated maximum emission wavelength,we predict that CH2-,NH-,and O-substituted BTD-based derivatives could be used as red,green,and orange light-emitting materials,respectively.After CH2-,NH-or O-substitution,the oscillator strengths of the emission spectra are enhanced with respect to that of the pristine molecule,implying that these compounds have larger fluorescence intensity.Finally,it can be deduced that CH2-,NH-,and O-substituted BTD-based derivatives may act as hole transport materials in organic light-emitting diodes.

Laser beam induced current microscopy and photocurrent mapping for junction characterization of infrared photodetectors

For non-destructive optical characterization, laser beam induced current(LBIC) microscopy has been developed into as a quantitative tool to examine individual photodiodes within a large pixel array. Two-dimensional LBIC microscopy, also generally called photocurrent mapping(PC mapping), can provide spatially resolved information about local electrical properties and p-n junction formation in photovoltaic infrared(including visible light) photodetectors from which it is possible to extract material and device parameters such as junction area, junction depth, diffusion length, leakage current position and minority carrier diffusion length etc. This paper presents a comprehensive review of research background, operating principle, fundamental issues, and applications of LBIC or PC mapping.

A novel crosslinkable electron injection/transporting material for solution processed polymer light-emitting diodes

A novel crosslinkable water/alcohol soluble conjugated polymer PFN-C containing oxetane groups and aminoalkyl groups in the side chains has been developed and used as highly efficient electron injection and transporting material for polymer light-emitting diodes (PLEDs). The unique solubility in polar solvents and crosslinkable ability of PFN-C render it a good can- didate for solution processed multilayer PLEDs. It was found that PFN-C can greatly enhance the electron injection from high work-function metal cathode, due to its pendant amino groups. As a result, PLEDs with PFN-C/Al cathode exhibited compara- ble device performance to the devices with Ba/Al cathode. The resulting green light-emitting device showed promising perfor- mance with a maximum luminance efficiency of 13.53 cd A-1.

Progress in small-molecule luminescent materials for organic light-emitting diodes

Organic light-emitting diodes （OLEDs） have been extensively studied since the first efficient device based on small molecular luminescent materials was reported by Tang. Organic electroluminescent material, one of the centerpieces of OLEDs, has been the focus of studies by many material scientists. To obtain high luminosity and to keep material costs low, a few remarkable design concepts have been developed. Aggregation-induced emission （AIE） materials were invented to overcome the common fluorescence-quenching problem, and cross-dipole stacking of fluorescent molecules was shown to be an effective method to get high solid-state luminescence. To exceed the limit of internal quantum efficiency of conventional fluorescent materials, phosphorescent materials were successfully applied in highly efficient electroluminescent devices. Most recently, delayed flu- orescent materials via reverse-intersystem crossing （RISC） from triplet to singlet and the ＂hot exciton＂ materials based on hy- bridized local and charge-transfer （HLCT） states were developed to he a new generation of low-cost luminescent materials as efficient as phosphorescent materials. In terms of the device-fabrication process, solution-processible small molecular lumi- nescent materials possess the advantages of high purity （vs. polymers） and low procession cost （vs. vacuum deposition）, which are garnering them increasing attention. Herein, we review the progress of the development of small-molecule luminescent materials with different design concepts and features, and also briefly examine future development tendencies of luminescent materials.

Experimental study of GaN based blue light emitting diodes with a thin AlInN layer in front of the electron blocking layer

The Ga N based blue light emitting diodes(LEDs) with a thin Al In N layer inserted in front of the electron blocking layer(EBL) are experimentally studied.It is found that inserting a thin EBL can improve the light output power and reduce the efficiency droop compared with the conventional Al Ga N counterparts.Based on numerical simulation and analysis,the improvement on the electrical and optical characteristics is mainly attributed to the reduction of the electron leakage current,which increases the concentration of carriers in the quantum well(QW) when the thin Al In N layer is used.

Stabilizing electroluminescence color of blue perovskite LEDs via amine group doping

Voltage loading-induced change in the electroluminescence(EL)wavelength of mixed halide perovskite light-emitting diodes(PeLEDs),so-called color-shift,has become an inevitable phenomenon,which is seriously unfavorable to their applications in lighting and display.Here,we achieve color-stable blue PeLEDs via a hydrogen-bonded amine-group doping strategy.Selecting guanidine(GA)or formamidinium(FA)as amine-group(-NH_(2))doping source for CsPbBr_(x)Cl_(3-x)quantum dots(QDs),experimental and theoretical results reveal that the strong N-H…X(X=Br/Cl)bonding can be produced between-NH_(2)dopants and Pb-X lattices,thereby increasing the migration barrier of halide anions.Resultantly,color-stable sky-blue devices were realized with emission peaks fixed at 490.5(GA)and 492.5(FA)nm without any obvious shift as the voltage increases,in sharp contrast devices without N-H…X producing a 15 nm red-shift from 487 to 502 nm.Not only that,maximum external quantum efficiency is improved to 3.02%and 4.14%from the initial 1.3%.This finding offers a convenient boulevard to achieve color-stable PeLEDs with high efficiency.

Thermally activated delayed fluorescence materialsensitized helicene enantiomer-based OLEDs:a new strategy for improving the efficiency of circularly polarized electroluminescence

A new strategy of thermally activated delayed fluorescence(TADF)material-sensitized circularly polarized luminescence(CPL)has been proposed for improving the efficiencies of fluorescent circularly polarized organic lightemitting diodes(OLEDs)(CP-OLEDs).Consequently,a pair of helicene enantiomers,(P)-HAI and(M)-HAI,were synthesized.The helicene enantiomers with the rigid helicalπ-skeleton had highly thermal and enantiomeric stabilities,and they also showed excellent photophysical properties,especially,intense mirror-image CPL activities with large luminescence dissymmetry factor(|g_(lum)|)values of about 6×10^(-3).Notably,the CP-OLEDs with the helicene enantiomers as emitters and a TADF molecule as sensitizer not only displayed better performance of lower turn-on voltage(V_(T))of 2.6 V,four-fold maxmium-external quantum efficiency(EQE_(max))of 5.3%,and lower efficiencies roll-off of 1.9%at 1000 cd m^(-2),than those of the devices without TADF sensitizer,but also exhibited intense circularly polarized electroluminescence(CPEL)with the electroluminescence dissymmetry factor(g_(EL))values of-2.3×10^(-3)and+3.0×10^(-3).Meanwhile,this study also represents the first thermally activated sensitized fluorescent CP-OLEDs with markedly enhanced efficiencies and intense CPEL.