Colour sensitive devices based on double p-i-n-i-p stacked photodiodes

In this work, we report on an amorphous silicon based image sensor with a bias voltage controllable spectral response characteristics. This multilayered device is composed by two stacked p-i-n-i-p structures produced by plasma enhanced chemical vapour deposition on a glass substrate and sandwiched between two transparent conductive oxide electrodes with a patterned molybdenum layer between the sensing and switching structures. Optical readout technique is used for image readout. Device performances have been evaluated from the current-voltage characteristics and spectral response measurements performed for the p-i-n-i-p test structures and stacked device. It is demonstrated that the device is sensitive to blue-green or red light depending on polarity of the bias voltage enabling the detection of colour images. Device design is discussed and supported by a numerical simulation.     

Stability of perovskite materials and devices

Due to the excellent optoelectronic properties, organic–inorganic perovskites have drawn much attention and have been applied in different electronics with remarkable performance. However, the poor stability creates a massive barrier for the commercialization of perovskite electronic devices. In this review, we discuss intrinsic and extrinsic factors causing instabilities of perovskites and perovskite devices such as solar cells, liquid crystal displays (LCDs), light emitting diodes (LEDs), ionizing radiation detectors, transistors, memristors and sensors. We further review the stabilization approaches, including composition engineering, adoption of lower dimensional compositions, quantum dots, interface engineering, defects engineering and so on.     

The effect of helium plasma etching on polymer-based optoelectronic devices

In this paper the optoelectronic performance of selectively patterned conjugated polymers in light emitting diodes (LEDs) and photodetectors was examined. Polymers were patterned via a dry, non-reactive ion etching process using helium plasma. The polymers studied were the light-emitting poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and poly[9,9-di-(2′-ethylhexyl)fluorenyl-2,7-diyl], and the conducting poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate). The electroluminescent spectra of etched and unetched LEDs are almost identical. There is no correlation between He-ion etching times and LED emission spectra changes. The MEH-PPV-based photodetectors show no decrease in external quantum efficiencies due to increased etch times. Results show that using helium plasma is effective at etching these polymers at predictable rates from selected areas without damaging the working device.     

Pure red organic electroluminescent devices using a novel europium(III) complex as emitting layer

Stable vacuum deposition of a new europium(III) complex, Eu(DBM)₃(L) {DBM=dibenzoylmethanato, L=3-ethyl-2-(4′-dimethylaminophenyl)imidazo[4,5-f]1,10-phenanthroline}, were verified by ultraviolet–visible and infrared spectroscopy. By using the vacuum deposited film of the Eu(III) complex as the emitting layer, aluminum tris(8-hydroxyquinolinate) (AlQ) as electron-transporting layer, 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) as hole-blocking layer, N,N′-diphenyl-N,N′-bis(3-methylphenyl)-1,1′-diphenyl-4,4′-diamine (TPD) as hole-transporting layer, a four-layer electroluminescent device of (+)indium–tin oxide/TPD(40 nm)/Eu(DBM)₃(L)(40 nm)/BCP(10 nm)/AlQ(40 nm)/Mg:Ag(110 nm)/Ag(60 nm)(−) gave high efficient and pure red light emission with a luminance of 230 cd/m². A comparison of the electroluminescence properties of the four-layer device with those of a two-layer and a three-layer device was made.     

Electrochromic materials and devices: Brief survey and new data on optical absorption in tungsten oxide and nickel oxide films

Current work on inorganic electrochromic materials and devices is reviewed briefly, and the emphasis on thin films of W oxide and Ni oxide is pointed out. New results are presented on the optical properties for sputter-deposited thin films of these two materials: for Li⁺ intercalated sub-stoichiometric W oxide, it is shown that the absorption can be reconciled with an extended “site saturation” model accounting for electronic transitions between W ions in 6+, 5+, and 4+ states, and for H⁺ deintercalated Ni oxide, it is found that the coloration efficiency is higher than in prior work presumably as a consequence of the nanocrystalline structure ensuing from the deposition conditions.     

高分辨率光电尺寸检测系统研究

论述了高分辨率光电尺寸检测系统的工作原理和系统总体结构，并给出了设计要点和提高系统分辨率的途径，本系统具有高速，高精度，非接触在线检测，测量结果直接数字显示和打印等特点。     

Optoelectronic and nonlinear optical processes in low dimensional semiconductors

Spatial confinement of quantum excitations on their characteristic wavelength scale in low dimensional materials offers unique possibilities to engineer the electronic structure and thereby control their physical properties by way of simple manipulation of geometrical parameters. This has led to an overwhelming interest in quasi-zero dimensional semiconductors or quantum dots as tunable materials for multitude of exciting applications in optoelectronic and nonlinear optical devices and quantum information processing. Large nonlinear optical response and high luminescence quantum yield expected in these systems is a consequence of huge enhancement of transition probabilities ensuing from quantum confinement. High quantum efficiency of photoluminescence, however, is not usually realized in the case of bare semiconductor nanoparticles owing to the presence of surface states. In this talk, I will focus on the role of quantum confinement and surface states in ascertaining nonlinear optical and optoelectronic properties of II–VI semiconductor quantum dots and their nanocomposites. I will also discuss the influence of nonlinear optical processes on their optoelectronic characteristics.     

Structuration and integration of magnetic nanoparticles on surfaces and devices

Different experimental approaches used for structuration of magnetic nanoparticles on surfaces are reviewed. Nanoparticles tend to organize on surfaces through self-assembly mechanisms controlled by non-covalent interactions which are modulated by their shape, size and morphology as well as by other external parameters such as the nature of the solvent or the capping layer. Further control on the structuration can be achieved by the use of external magnetic fields or other structuring techniques, mainly lithographic or atomic force microscopy (AFM)-based techniques. Moreover, results can be improved by chemical functionalization or the use of biological templates. Chemical functionalization of the nanoparticles and/or the surface ensures a proper stability as well as control of the formation of a (sub)monolayer. On the other hand, the use of biological templates facilitates the structuration of several families of nanoparticles, which otherwise may be difficult to form, simply by establishing the experimental conditions required for the structuration of the organic capsule. All these experimental efforts are directed ultimately to the integration of magnetic nanoparticles in sensors which constitute the future generation of hybrid magnetic devices.     

Photoelectrical properties of protein-based optoelectronic sensor

Bacteriorhodopsin (BR) has been studied as a biomaterial for molecular computing applications. Thin film elements based on BR in polyvinylalcohol were prepared to determine the photoelectrical properties of the material for the development of an optoelectronic sensor. The properties were studied by registering the photovoltage in time, measuring the intensity, area and wavelength dependence of the photoelectric response, and evaluating the element quality. The thin film elements produce a stable photovoltage, the intensity and area dependencies are close to linear, and the wavelength dependence is closely related to the absorption spectrum of BR. The homogeneity of the element thin films is good based on the relatively small variance of the photoelectric response, thus it is feasible to continue the development of an artificial retina based on BR.     

Recent Advances in Biointegrated Optoelectronic Devices

With recent progress in the design of materials and mechanics, opportunities have arisen to improve optoelectronic devices, circuits, and systems in curved, flexible, stretchable, and biocompatible formats, thereby enabling integration of customized optoelectronic devices and biological systems. Here, the core material technologies of biointegrated optoelectronic platforms are discussed. An overview of the design and fabrication methods to form semiconductor materials and devices in flexible and stretchable formats is presented, strategies incorporating various heterogeneous substrates, interfaces, and encapsulants are discussed, and their applications in biomimetic, wearable, and implantable systems are highlighted.     

Single-layer small molecular organic light emitting diodes without hole transport layer

Organic light emitting devices based on tris-8-hydroxyquinoline aluminum with an ultra-thin insulating film instead of a hole-transporting layer were investigated. Three kinds of single-layer devices were fabricated with silicon dioxide (SiO₂), alumina (Al₂O₃) or polytetrafluoroethylene (Teflon™) as the insulating films, and they showed better performance than devices without insulating films. The hole injection of these devices was also investigated using hole-only devices. The holes injection enhancement by tunneling effect and electrons blocking of the ultra-thin insulating layers were experimentally proved to have yielded high performance of single-layer devices.     

Enhancement of green electroluminescence from 2,5-di-p-anisyl-isobenzofuran by double-layer doping strategy

A highly fluorescent compound, 2,5-di-p-anisyl-isobenzofuran (DABF), was synthesized and used as a dopant to fabricate efficient green electroluminescence (EL) devices. The highest occupied molecular orbital level of DABF suggests that it can be excited either by energy transfer or by direct charge trapping mechanism in the EL devices. Three kinds of devices were fabricated based on different emission mechanisms. A double-layer-doped device with DABF doped in both the hole-transporting layer and the electron-transporting layer of the ITO/NPB/TPBI/Mg:Ag device, where ITO is indium-tin-oxide, NPB is (4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl), and TPBI is (2,2′,2″-(1,3,5-benzenetriyl)tris[1-phenyl-1H-benzimidazole]), exhibited greatly enhanced brightness and efficiency comparing to the single-layer-doped devices. The brightness and efficiency enhancements are attributed to a combined contribution of energy transfer and direct charge trapping mechanisms in the double-layer-doped device.     

Photo- and electroluminescence properties of fluorene-based copolymers containing electron- or hole-transporting unit

We report the photophysical and electroluminescence (EL) properties of two fluorene-based copolymers, poly{[9,9-bis(2-ethylhexyl)fluorene-2,7-diyl]-alt-[6,6′- bis(3-phenylquinoxaline)-2,2′-diyl]} (Qx-PF) and poly{[9,9-bis(2- ethylhexyl)fluorene-2,7-diyl]-alt-[N,N′-diphenyl-N,N′-bis(4-phenyl)-1,1′-biphenyl-4,4′-diamine]} (TPD-PF). The two copolymers in thin films show blue emission approximately 429-452 nm with relatively narrow bandwidth upon photoexcitation. Electroluminescence has been demonstrated using TPD-PF as the active polymer in the light-emitting electrochemical cell (LEC) with a turn-on voltage at 2.8 V and an EL efficiency of 0.002 cd/A. Due to the improved electron-transporting property, the Qx-PF-based LEC achieves the EL efficiency of 0.07 cd/A, 35 times higher than that of the TPD-PF-based device. Compared to the photoluminescence spectra, EL spectra show enhanced excimer emission, which is primarily related to self-heating of the devices during operation. The main process involved in the decrease of the light intensity during device operation is the electrochemical degradation of the polymer blend.     

Improved host material design for phosphorescent guest-host systems

A series of proposed carbazole-based compounds are studied as host materials in an iridium phosphor-based guest-host organic light-emitting diode. Semi-empirical calculations are performed on each compound to predict its efficacy as a host material, and these theoretical predictions are compared to device performance for each compound, in an attempt to verify the model.     

Characteristics improvement of metalorganic chemical vapor deposition grown MgZnO films by MgO buffer layers

MgZnO films with a small quantity of Mg were grown on c-sapphire substrates coated with a thin MgO buffer layers by metalorganic chemical vapor deposition. The MgO buffer layer causes improvement in the structural, optical, and electrical properties of subsequently deposited MgZnO thin films, when compared to MgZnO films deposited without a buffer layer. The MgZnO films with a MgO buffer layer grown at 330 °C showed the best performance. Transmission electron microscopy revealed that the cubic phase MgO buffer layer promoted the epitaxial behavior of MgZnO, where the planar relationships of the wurtzite-MgZnO/cubic-MgO/sapphire heterostructures mainly were MgZnO(0001)//MgO(001)//sapphire(0001) and MgZnO(11?00)//MgO(110)//sapphire(112?0). It resulted in lower lattice mismatch between MgO and MgZnO by domain epitaxy of 2/1 and enhancement in preferred growth of the MgZnO films along the c-axis.     

SiGe/Si异质结光电器件

SiGe/Si异质结光电器件及其光电集成(OEIC)是硅基光电研究的一个非常引人注目的领域.综述了SiGe/Si异质结材料的基本性质,SiGe/Si异质结光电器件的结构、性能、应用及其光电集成.重点介绍了SiGe/Si光电探测器及其与其他相关器件的集成.