以陶瓷厚膜为绝缘层的电致发光器件

使用PbMg1/3Nb2/3O3-PbTiO3-PbCd1/2W1/2O3三元系电容器瓷料,采用流延工艺成膜,丝网印刷内电极,低温烧结的方法制备了陶瓷衬底。陶瓷衬底的烧结温度为930－950^0C。测量了陶瓷厚膜的基本特性,在室温时的相对介电常数εr大于14000,损耗tanδ约为1％,具有极高的品质因素（≥80μC/cm^2）。用SEM技术观察了陶瓷衬底的横断面和陶瓷厚膜表面形貌,内电极连续,厚膜层致密且表面起伏较小,可直接沉积发光层。制备了陶瓷厚膜为绝缘层的ZnS:Mn低压驱动电致发光器件,在50Hz正弦波驱动下,阈值电压仅为41V。     

以陶瓷厚膜为绝缘层的电致发光器件研究

研制了以四元系组分ＰＭＮ－ＰＴ－ＰＦＮ－ＰＣＷ陶瓷厚膜为绝缘层的电致发光器件，对陶瓷厚膜的制备条件和制得的厚膜与器件的发光性能的关系进行主详细的研究。特别对基片要求和印刷烧制等工艺进行了探讨。     

聚3,4-乙烯二氧噻吩/聚苯乙烯磺酸复合LB膜在OLED器件上的应用

采用Langmuir-Blodgett(LB)膜静电诱导沉积法制备聚3,4-乙烯二氧噻吩(PEDOT)高度有序导电聚合物复合薄膜,研究了薄膜的导电性能并进一步研究薄膜在改善器件性能方面的作用.并将其应用于有机电致发光二极管(OLED)器件的空穴缓冲层,将聚3,4-乙烯二氧噻吩/聚苯乙烯磺酸(PEDOT/PSS)复合LB沉积于纳米铟锡金属氧化物(ITO)电极上,制备了以复合LB膜为空穴缓冲层的OLED器件.发现复合LB膜改善了器件性能(启动电压降低,最大亮度增加),但进一步的研究表明LB膜器件在一定时间后出现性能劣化.I-V特性和X射线反射率(XRR)分析表明,薄膜的结构发生一定程度的改变是导致器件性能变差的可能原因.     

CuPc/ZnS多层复合薄膜的制备及光电性能的研究

为了找到制备具有最佳光电导性能的CuPc/ZnS多层复合薄膜的工艺参数 ,研究了CuPc/ZnS多层复合膜的层数系列、CuPc膜层的厚度系列、ZnS膜层的厚度系列和基板温度系列的光电导性能和结构。利用表面电位衰减、紫外 可见光谱和X射线衍射分析了复合薄膜的光电导性能和结构及其关系 ,探讨了改变复合膜层数、CuPc膜层和ZnS膜层的厚度以及基板温度对CuPc/ZnS多层复合薄膜的光电导性能和结构的影响     

CuPc／ZnS多层复合薄膜的制备及光电性能的研究

为了找到制备具有最佳光电导性能的CuPc/ZnS多层复合薄膜的工艺参数，研究了CuPc/ZnS多层复合膜的层数系列、CuPc膜层的厚度系列、ZnS膜层的厚度系列和基板温度系列的光电导性能和结构。利用表面电位衰减、紫外－可见光谱和X射线衍射分析了复合薄膜的光电导性能和结构及其关系，探讨了改变复合膜层数、CuPc膜层和ZnS膜层的厚度以及基板温度对CuPc/ZnS多层复合薄膜的光电导性能和结构的影响。     

Mn,Cu掺杂对ZnS∶Mn,Cu电致发光材料亮度的影响

采用水热法制备了ZnS∶Mn,Cu电致发光材料,利用透射电镜对发光材料的结构和形貌进行表征,并且探讨了Cu2+、Mn2+掺杂量和反应温度对ZnS∶Mn,Cu发光材料亮度的影响。结果显示,随着Cu2+、Mn2+掺杂量的增加,发光材料的亮度也随之增加,但对于Cu2+、Mn2+掺杂都存在最佳值,当Cu2+掺杂量0.2%,Mn2+掺杂量4%,温度150℃时,得到的电致发光材料亮度较高,粒径约10nm左右。     

电泳沉积法制备锶铁氧体厚膜

通过表面活性剂十二烷基苯磺酸(DBSA)包覆锶铁氧体,在1-丁醇中制备了稳定的悬浮液并成功电泳沉积锶铁氧体厚膜。从理论和实验上研究了沉积量及膜厚与电场强度、电泳时间和电极距离等的关系。结果表明电泳法能够制备质量优异的锶铁氧体厚膜,但沉积条件对厚膜有重要影响。烧结温度为1000℃时可获得磁性能良好的厚膜,其比饱和磁化强度为45A·m2/kg,剩磁比为0.556,矫顽力为4840Oe。经过分步沉积膜厚可达40μm左右。利用该方法制备的膜可用于设计带宽较宽的非互易微波铁氧体器件。     

ZnS：Ag^＋AC TFEL器件的制备及发光特性研究

通过对ZnS:Ag^ 薄膜电致发光（TFEL）器件的光学性质的研究，探讨了能获得稳定兰色发光的TFEL器件的制备及有利于ZnS:Ag^ 兰色发光的实验条件，同时讨论了光的干涉对ZnS:Ag^ TFEL光谱的影响，在实验中得到的ZnS:Ag^ TFEL光谱是包含几个隆起的宽带，通过计算证明这些隆起的出现与光的干涉有关。Ag^ 的浓度对ZnS:Ag^ TFEL器件的发光亮度和稳定性有显著的影响，Ag^ 浓度约为0.03mol%时，器件亮度较高，稳定性也较好，浓度再大时，亮度和稳定性较低，较高的电压有利于ZnS:Ag^ 兰色发光的提高，激发频率也存在一个最佳值。     

CdSe胶质量子点的电致发光特性研究

采用胶体化学法合成硒化镉(CdSe)胶质量子点, 在此基础上制成了以CdSe胶质量子点为有源层, 结构为ITO/ZnS/CdSe/ZnS/Al的电致发光(EL)器件. 透射电镜测量表明量子点的尺寸为4.3 nm, 扫描电子显微镜测量ZnS薄膜和Al薄膜结果显示表面均较为平整, 由器件结构的X射线衍射分析观察到了CdSe(111)、ZnS(111)等晶面的衍射, 表明器件中包含了CdSe量子点和ZnS绝缘层材料. 光致发光谱表征胶质量子点的室温发光峰位于614 nm, 电致发光测量得到器件在室温下的发光波长位于450 ~ 850 nm, 峰值在800 nm附近. 本文对电致发光机制及其与光致发光谱的区别进行了讨论.     

无机EL显示器件用高性能介电层的研究

用rf和反应磁控溅射法成功制备了一种总厚度为530～730nm的SrTiO3/Ta2O5复合介电层,获得在500Hz下介电常数为48～73,反映介电损耗的参数ΔVy在0.06～0.15V之间,击穿场强为106～139MV/m,在0.05V/nm的电场下正、反向漏电流在10-9～10-7A/cm2之间,品质因子(εrεoEb)大于5μc/cm2.同时比较了SrTiO3/Ta2O5复合介电层和SrTiO3和Ta2O5单层薄膜的介电性能.把复合膜应用于以ZnS:Mn和Zn2Si0.5Ge0.5O4:Mn为发光材料的器件中,获得了适当的阈值电压和较高的亮度.     

Sputter deposition of ZnS:Mn/SrS:Ce multilayered thin film white phosphor

A full color thin film electroluminescent (TFEL) display can be fabricated by using color filters in combination with a high efficiency ‘white’ phosphor, such as a thin film multilayered stack of ZnS:Mn and SrS:Ce (denoted ZnS:Mn/SrS:Ce). To date, deposition of these multilayers has been limited to vacuum evaporation techniques and atomic layer epitaxy, both of which require different substrate temperatures for growth of high quality ZnS:Mn and SrS:Ce. This repeated thermal cycling during multilayer deposition can adversely affect electroluminescent (EL) performance and manufacturability. Sputter deposition of ZnS:Mn and SrS:Ce produces high quality phosphors for a wider range of substrate temperatures. We have determined a common set of radio frequency (rf) sputter deposition parameters for ZnS:Mn and SrS:Ce that result in high performance, multilayered white phosphors for use in TFEL devices. The EL performance of our samples is comparable to the best performance reported for evaporated multilayered samples. The major improvement is that the rf sputtered ZnS:Mn and SrS:Ce layers were deposited at the same substrate temperature. We report on the effects of sputter deposition parameters on the resultant composition and morphology of ZnS:Mn and SrS:Ce thin films and multilayers. Their EL performance was evaluated and correlated to composition and morphology.     

Effects of insulating layer on the performance of thin film electroluminescent devices

Thin film electroluminescent devices were fabricated with active layer of ZnS:Mn and different insulators viz Sm₂O₃, Eu₂O₃, Na₃A1F₆, MgF₂, CeO₂ and SiO in MIS and MISIM structure. The threshold voltage for light emission in AC thin film electroluminescent devices of MIS and MISIM structures is found to depend on the dielectric properties of insulating materials. The observed threshold voltage for these devices and its variations for devices with different insulators are explained using the equivalent circuit for the device and the dielectric properties of the insulting material used for the preparation of device. Variation of threshold voltage with operating time is also studied for some of the devices.     

To increase the lifetime of electroluminescent (EL) device by low-temperature deposition of organic thin solid films

We have studied the electrical and light-emitting behaviour as well as the lifetime of electroluminescent (EL) cells which consist of naphthoylimide (NPL) as the emitting layer and poly(3-octythiophene) (P3OT) doped with poly(N-vinylcarbazoe) (PVK) as the hole transport layer sandwiched between indium-tin-oxide (ITO) and aluminium (Al) electrodes. The mixed polymer (P3OT : PVK) layer and the emitting layer were deposited by spin coating and by vacuum deposition. When the ITO substrate was cooled to near liquid N2 temperature during the deposition of the NPL emitting layer, the brightness of the cells increased. Characterized by atomic force microscopy (AFM), the emitting layer became more amorphous as the deposition temperature decreased. Results collected show that low temperature deposition of organic thin solid films would be a powerful technique for not only the enhancement of electroluminescent brightness but also increasing the lifetime of EL devices. © 1998 Kluwer Academic Publishers     

Effect of Cu x S layer on d.c. thin film electroluminescent devices

Electroluminescent properties of thin film devices with ZnS activated with rare earth and manganese are reported. The devices were prepared by a method involving a three-step process, namely evaporation of ZnS, dipping in CuCl solution and evaporation of ZnS:A, Cl (A = Mn, Sm, Dy, Pr) layer. The electroluminescent emission spectra show an emission characteristic of copper in addition to that of the dopant. The current-voltage characteristic of the device indicate that there is a Cu _x S/ZnS:A, Cl heterojunction.     

The characteristics of inorganic electroluminescent devices with an amorphous diamond film as cathode material

Diamond like carbon (DLC) thin films were used as the cathode layers of inorganic alternating current driven thick dielectric electroluminescent devices. The results indicated that electroluminescent (EL) devices with DLC cathode has superior brightness over the EL with Al or Cr-doped DLC cathodes. Cr-doping in DLC thin film can increase the electrical conductivity, but degrades the EL properties. Also, the EL device with DLC cathode possesses the lowest decay rate among various cathodes, because of the high thermal conductivity and the inert nature of DLC film.     

Characteristics of a.c. electroluminescence in thin film ZnS : Mn display devices

Thin film electroluminescence (TFEL) displays are complex optoelectronic devices with challenging material requirement. The electrical characteristics of ZnS : Mn alternating current thin film electroluminescent devices grown by electron beam evaporation are assessed as function of voltage frequency and Mn concentration. The threshold voltage increases with increasing frequency of the applied voltage and saturation value of electroluminescence (EL) brightness increases linearly with the frequency of applied voltage. The EL brightness increases linearly with the frequency of the applied voltage. The EL brightness was found optimum for a particular activator concentration. A model is proposed and an expression is derived for the EL brightness, which is able to explain the dependence of the EL brightness on different parameters.     

Control of ZnO thin film surface by ZnS passivation to enhance photoluminescence

To enhance the optical property of zinc oxide (ZnO) thin film, zinc sulfide (ZnS) thin films were formed on the interfaces of ZnO thin film as a passivation and a substrate layer. ZnO and ZnS thin films were deposited by atomic layer deposition (ALD) using diethyl zinc, H₂O, and H₂S as precursors. Investigations by X-ray diffraction and transmission electron microscopy showed that ZnS/ZnO/ZnS multi-layer thin films with clear boundaries were achieved by ALD and that each film layer had its own polycrystalline phase. The intensity of the photoluminescence of the ZnO thin film was enhanced as the thickness of the ZnO thin film increased and as ZnS passivation was applied onto the ZnO thin film interfaces.     

Thin film light amplifier

A light amplifier was made from two separate thin film elements. The first of these elements, a photoconductive component, was a copper- and chlorine-doped CdS thin film evaporated under vacuum. The second was a thin film electroluminescent cell with a copper-, chlorine- and manganese-doped ZnS phosphor layer. The brightness B of the electroluminescent cell for various illumination levels L of the photoconductive layer was measured when the amplifier was excited with an alternating voltage of fixed amplitude and frequency. The results obtained experimentally showed fair agreement with the characteristics calculated from the proposed theoretical model.     

Preparation and properties of thin ZnS:Cu films phosphors

Thin films of ZnS and ZnS:Cu were prepared by an original metalorganic chemical vapour deposition (MOCVD) method under atmospheric pressure onto a glass substrate heated up to 230–250 °C. The film thickness varied from 0.6 to 1 μm. The thin films were doped with Cu and Cl by the thermal treatment during 1 h at 600 °C at atmospheric pressure in the blend composed of a ZnS powder with Cu and Cl compounds. These films were used for fabrication of the thin film electroluminescent (TFEL) devices with a conventional double insulating structure. The structural properties were investigated by use of X-ray diffraction (XRD) techniques and atomic force microscopy (AFM). Electroluminescent (EL) spectra, electrical and EL characteristics were investigated. The EL spectra and characteristics as well as structural parameters depend on the growth conditions and significantly modified after the annealing. Blue color emission with brightness of 10 cd m^− 2 under a sine wave excitation at 60 V and 5 kHz was obtained. The degradation behavior of the TFEL devices with ZnS:[Cu, Cl] films fabricated using an original non-vacuum methods of deposition and annealing is the same as that of commercial thin film phosphor.     

Determination of the parameters of phosphor activators in thin-film electroluminescent capacitor structures

A method for determining the concentration and electron-impact excitation cross section of activated emission centers in the phosphor layer of a thin-film electroluminescent capacitor structure, based on measurements of the brightness as a function of the applied alternating voltage amplitude and frequency, is analyzed. The error of determination of the parameters of electroluminescence excited by alternating-sign ramp voltage is evaluated. The parameters of electroluminescent structures based on the ZnS:Mn, ZnS:TbF₃, and ZnS:SmF₃ films are presented.