柔性电致变色器件研究进展

电致变色材料是一类重要的光电功能材料,可以随周期性调整的电压改变颜色.这种可控的光学吸收率和透过率的调制在智能窗户、电致变色显示和防眩光后视镜等应用场合大显身手.近年来电致变色技术发展迅速,但当前的研究大多集中在传统刚性电致变色器件,通常以氧化铟锡(ITO)等导电玻璃为基底.这些刚性变色器件存在厚度大、共型性差、机械强...     

无机全固态电致变色材料与器件研究进展

智能场致变色材料是一类能在外场(电场、温度、光照、气氛)刺激下发生可逆光学变化的物质群。其中,电致变色材料因其调节幅度大、响应速率快、着色效率高和循环稳定性好等特点,有望在智能窗、屏幕显示和多功能储能器件等领域得到广泛应用。相较于半固态电致变色器件难于封装以及有机电致变色材料易于变性失效,无机全固态电致变色材料及其器件具有更好的综合应用性。本文聚焦典型无机全固态电致变色材料与器件,综述了当前电致变色器件各结构层的制备途径,并对比了其优劣性,详细介绍了主要的电致变色备选材料及其关键性能评价指标,并阐释了几种代表性电致变色器件的作用原理,提出了使用兼具高透光率、低面电阻以及优异抗弯折性的透明柔性电极替代传统的刚性衬底以实现多场响应器件的应用拓展。最后,从性能瓶颈、工艺难点及产业化机遇的角度对无机全固态电致变色器件的应用前景进行了展望,为电致变色产业化进程提供了借鉴。     

导电聚合物PEDOT:PSS纸基印刷成膜和变色器件的制备

目的 以导电聚合物PEDOT:PSS作为电极和电致变色材料,通过棒涂、丝网印刷和凹版印刷等3种方式,实现导电聚合物纸基电致变色器件的制备.方法 通过溶剂(二甲基亚砜、异丙醇、甲醇、乙二醇、聚乙烯醇)掺杂的方式对3种印刷成膜特性进行优化;使用丙三醇提高PEDOT:PSS薄膜的导电性,采用PEDOT:PSS制作器件的变色层和电极层,简化变色器件结构.分别对变色器件的启动电压、变色效果、紫外吸收和弯曲等性能进行评价.结果 3种印刷方式均能实现纸基变色器件的制备,其中以凹版印刷方式制备的变色器件具有最佳的变色性能,即启动电压低(U=0.18 V)、响应时间短(t=2 s)、色差变化大(ΔE*=25.54),变色前后吸光度变化大(0.27),弯曲循环1000次后色差变化为1.结论 电致变色器件可以通过印刷的方式在纸基材料上进行制备,将纸基电致变色器件与印刷包装产品相结合,不仅能提高产品包装的外观表现,还可以增加产品包装的技术水平.     

电致变色器件关键材料凝胶聚合物电解质研究进展

凝胶聚合物电解质是构成电致变色器件(ECD)的关键材料,其在器件中作为电极间的传导介质,为电致变色反应提供补偿离子。利用不同基体材料制备的凝胶聚合物电解质对提高电致变色器件性能具有重要影响。综述了聚环氧乙烷(PEO)、聚丙烯腈(PAN)、聚甲基丙烯酸甲酯(PMMA)、聚偏氟乙烯(PVDF)、聚偏氟乙烯-六氟丙烯(PVDF-HFP)、聚乙烯醇缩丁醛(PVB)及生物材料作为凝胶电解质聚合物基体的导电机理。阐述了它们作为电致变色器件电解质层对离子电导率、透光度、电致变色性能的影响。最后对凝胶聚合物电解质未来发展趋势进行了展望。     

聚邻甲基苯胺的电化学合成与电色及光伏性能

为了得到平整并与基底结合牢固的聚邻甲苯胺,使之在电致变色和光伏材料上得到应用,用电化学的方法在ITO电极上制备了聚邻甲苯胺.考察了聚合条件对成膜的影响,对聚合物薄膜进行了红外、拉曼、紫外、荧光等结构表征,利用电子扫描显微镜(SEM)观测了复合膜形貌特征,采用原位电化学-光谱技术研究了聚合物的电致变色行为.首次以聚邻甲苯胺/TiO2复合膜为工作电极,铂电极为对电极,制成太阳能电池模型,测试了器件的光伏性能.研究表明:在聚合条件为单体浓度0.2 mol/L,硫酸浓度在0.5～1 mol/L、扫描速度0.02 V/s、扫描电压0～1.0 V时得到膜牢固平整;薄膜呈现岛状突起结构;电压从0增加至0.8 V,薄膜颜色从绿到蓝变化,且过程可逆;复合电极显示出明显的光伏特性.因此,说明聚邻甲苯胺是一种双功能性材料.     

无机电致变色材料反射特性研究进展

电致变色材料是一种在外加电场下, 颜色可以发生可逆转变的材料。电致变色材料可调的光谱范围广, 可以实现从可见到中远红外的宽波段调控, 在智能窗、显示、防炫目后视镜、智能热控和伪装等领域具有广泛应用前景。目前对无机电致变色材料的研究大多是关于透过特性的研究, 对于反射特性的研究较少, 这主要是因为无机变色材料大多颜色单一, 且不如有机变色材料容易设计。近年来, 通过一些特殊的制备方法和结构设计, 无机变色材料反射特性的研究逐渐受到科研人员的重视。本文从无机电致变色材料的反射特性出发, 详细介绍了无机电致变色在可见-近红外到中远红外波段的反射光谱调控方法和原理, 综述了最新研究进展。在可见波段, 反射特性调控主要通过制备五氧化二钒及其掺杂化合物、一维光子晶体微结构、法布里-珀罗纳米谐振腔结构和局域表面等离子共振等方式实现。在红外波段, 主要利用氧化钨等材料的分子振动吸收和德鲁德自由电子气体理论等理论设计制备红外反射型电致变色器件。最后, 对未来无机电致变色材料反射调节的实际应用进行了展望。     

电子束蒸发制备氧化钨、氧化镍薄膜的电致变色性能

电致变色(EC)材料在外加电压作用下能可逆地改变其光学性能.其中氧化钨与氧化镍是典型的电致变色用材料.本文用电子束蒸发的方法在ITO玻璃基片上制备了此两种薄膜,研究了热处理工艺对薄膜结构与电致变色性能的影响.电致变色性能由电化学方法测试.封装的半固态智能窗器件具有很好的电致变色性能.     

聚苯胺红外电致变色器件研究进展

电致变色是材料反射、吸收等光学性质在外加电场驱动下发生稳定、可逆变化的现象,在不同波段可表现为颜色、红外发射率等变化。红外电致变色器件(IR-ECDs)能够动态调节物体的红外光学特性,在自适应伪装、热管理等应用中受到广泛关注。作为最有代表性的有机电致变色材料,聚苯胺(PANI)制备方法简单,电化学性能优异,在多波段电致变色领域有着巨大的潜在应用价值。本文从电致变色器件结构出发,介绍了从可见电致变色到红外电致变色的原理和器件结构的演变,对近年来增强聚苯胺红外电致变色器件性能的策略和最新进展进行了归纳和分析,讨论了其多功能化应用的拓展方向,最后对所面临的挑战与未来的发展方向进行了总结与展望,为今后发展优异性能的IR-ECDs提供了参考,希望能够对本领域研究者有所启发,促进电致变色领域的发展。     

电致变色材料及器件的研究进展

电致变色材料被认为是目前最有应用前景的智能材料之一,在过去几十年里被广泛研究,相关的电致变色器件也已经上市。本文在总结了各种电致变色材料的变色机理及其成膜方法(重点介绍了本实验室采用射频溅射制备的WO3膜和NiO3膜)的基础上,研究了材料的应用及器件的组装，并对器件组装中所需要的部分其它关键材料进行了介绍。最后对未来电致变色材料及其应用进行了展望。     

层状自组装聚苯胺纳米复合电致变色薄膜的制备与性能

质轻、柔性、多色电致变色材料是柔性电致变色显示技术实用化、进而取代目前阴极射线管和液晶显示技术的关键。主链共轭型本征态导电聚合物聚苯胺因其原料来源广泛、转换电势低、变色范围宽、易于制成柔性薄膜而成为制备全固态柔性电致变色器件的首选材料。基于静电作用的层状自组装技术，能在分子层次上实现诸多材料的复合，并实现结构与性能的调控，因此成为设计组装具有特定性能的聚苯胺纳米复合电致变色薄膜的重要方法。讨论了层状自组装聚苯胺纳米复合电致变色薄膜的制备与性能，认为采用结构与性能可控的纳米结构层状自组装技术制备聚苯胺纳米复合电致变色薄膜是提高其综合性能并最终实用化的重要途径。     

水解聚丙烯腈/大豆分离蛋白凝胶纤维的电刺激性能

采用水解聚丙烯腈(HPAN)和大豆分离蛋白(SPI)的共混水溶液复合得到纺丝原液,用自制纺丝设备挤到含一定量戊二醛和浓硫酸的饱和Na2SO4水溶液的凝固浴中,交联成型、拉伸干燥得到HPAN/SPI响应性水凝胶纤维,研究了电刺激性能.结果表明,在电解质溶液中非接触直流电场作用下,HPAN/SPI水凝胶纤维具有电流刺激响应性,表现为凝胶纤维弯曲现象.随着凝胶网络中-COOH含量的增加,纤维的弯曲度成阶段性增加,较高的聚丙烯腈含量使这种变化更为明显.HPAN/SPI水凝胶交联度、离子强度和pH的变化使得弯曲先增大后减少.在非直流电场的作用下,在wPAN=0.6,Na2SO4浓度为0.10 mol/L,pH=11水溶液中,电场强度为20 V时凝胶纤维的弯曲率达到极大值.该比例的HPAN/SPI凝胶纤维在Shiga凝胶弯曲理论中的Y取极大值.     

PS/PAN嵌段共聚物静电纺纳米纤维及其衍生物的吸附性

通过静电纺丝技术制备PS/PAN嵌段共聚物纳米纤维毡,主要研究制备过程中PS/PAN浓度、电压、收集距离等对PS/PAN纳米纤维形貌、尺寸的影响,分析静电纺PS/PAN纳米纤维毡及其水解衍生物对镍、铅离子和阳离子染料的吸附性。结果表明,合适电纺条件为PS/PAN嵌段共聚物浓度8%、电压20kV、收集距离10cm;PS/PAN嵌段共聚物纳米纤维毡水解衍生物对镍、铅离子和阳离子染料有较好的吸附性。     

聚丙烯腈基碳纳米纤维在超级电容器电极材料中的应用研究进展

超级电容器是一种介于电池和传统物理电容器之间的新型环保储能器件,近年来得到了研究者的广泛关注。电极材料是超级电容器的核心部分,因此具有更高的研究价值。聚丙烯腈基碳纳米纤维因具有良好的静电纺丝性、较高的碳化产率、优异的纳米结构、超高的比表面积以及优良的导电性和稳定性,已经成为超级电容器电极材料的研究热点。本文主要介绍了聚丙烯腈基交联结构和多孔结构碳纳米纤维电极材料,元素掺杂电极材料以及与碳材料、导电聚合物、金属氧化物复合的电极材料,并对聚丙烯腈基碳纳米纤维电极材料未来的研究方向进行了展望。     

Built-in voltage in organic light-emitting diodes with a use of Li2O/Al cathode

An effect of bilayer cathode Li2O/Al system was studied in Alq3 based organic light-emitting diodes with a variation of Li2O layer thickness from 0 to 10 nm. The device was made in a structure of ITO/(TPD)/Alq3/Li2O/Al. Current density-luminance-voltage (J-L-V) characteristics and a built-in voltage of the device were measured at ambient conditions. Built-in voltage in the device is generated due to a difference of work functions between the anode and cathode. From the J-L-V characteristics of the device, we observed an increase in luminance and current efficiency by more than 100 times and 2 times, respectively, for the device with 0.5 nm thick Li2O layer. The measured built-in voltage shows that the device with 0.5 nm thick Li2O layer has relatively higher built-in voltage compared to the others. Since the higher value of built-in voltage corresponds to the lower value of electron barrier height in cathode, the improvement in the efficiency for the device with 0.5 nm thick Li2O layer is thought to be due to a lowering of the electron barrier height.     

Sampling time effects in the ACT device

The signal-dependent sampling process in an acoustic charge transport (ACT) device is demonstrated. Theoretical calculations and experimental measurements show the direct effect of gate voltage, wave amplitude, and transport depth on the sampling interval. A decrease in gate voltage and transport depth, and an increase in wave amplitude, are shown to reduce the increase in sampling time delay for a fixed transport current. An analysis of the distortion generated by this nonuniform sampling is performed, and a channel-current-intercept value is computed for a typical ACT device.     

结合边缘特征的遥感图像融合

曲波(Curvelet)变换是一种更适合于图像处理的多尺度几何分析(MGA)方法,具有很强的方向性.结合 HSI变换将其应用于全色图像和多光谱(MS)图像融合可以更好地表示图像中的有用特征.首先对多光谱图像进行 HSI变换,得到亮度分量 I,对全色图像和 I 分量进行曲波变换得到粗尺度系数和细节尺度系数,对全色图像的粗尺度系数和细节尺度系数进行叠加,计算归一化的全色曲波系数直方图,定义边缘有效因子,利用全色图像的特征信息对融合图像的粗尺度系数进行处理,对细节尺度系数采用函数对弱边缘进行增强,对新的曲波系数设计融合规则进行融合,逆变换后得到新的亮度分量 Inew,用 Inew 替代原亮度分量 I 进行逆 HSI 变换得到最终融合结果,采用统计类指标对融合结果进行评价.实验结果表明,该方法在保持光谱信息和提高空间分辨率上都有较好的效果.     

A Design of a Period-to-Frequency Analog Converter

A method for designing a period-to-analog converter is described. The device accepts input signals of varying frequency and converts the period of the waveform to a time inverse voltage Vi(t). This voltage is sampled at the end of the period, and this information is held over the following interval. The analog derived from the input signal is a voltage proportional to the repetition rate. The approach to generating the time inverse voltage is based on Willer's general method of approximating decaying functions with a sum of exponential functions. The described method has been utilized to develop a device for monitoring physiological signals. Results demonstrating the performance of the instrument are presented. The method is directly applicable to function generation in general and could be of importance for analog computers.     

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.     

Visible-infrared spectral response of microcrystalline hydrogenated silicon hetero-junctions

Microcrystalline p–i–n devices with an increased infrared sensitivity infrared sensitivity are prepared by the closed-chamber cyclic technique.The spectral response for different applied bias, the current–voltage characteristics at different wavelengths and the photocurrent delivered by the device are analysed. The spectral response is extended far beyond the amorphous limit of about 750 nm and even at a wavelength of 1000 nm, the response is still at a level of about 5% of the maximum. The good near infrared sensitivity is considered to be a result of the large optical absorption ascribed to the crystalline phase. Under reverse bias, the spectral response is high and essentially unchanged, reflecting a good collection efficiency. Under increasing forward bias, up to values near the open-circuit voltage, it decreases continuously, but even at much higher bias (up to about 0.8 V), the device produces a photocurrent.A heterojunction model based on the growth mechanism of the device and supported by a numerical simulation is presented to explain this behaviour.     

The operation characteristics of a thin film CdSe transducer

CdSe thin films and CdSe thin film active transducers (TFAT) have been studied under similar deposition conditions in an attempt to understand closely the dynamic anomalous behavior reported earlier. The observance of a positive and negative change in drain current on the application of a positive strain, according as the applied gate voltage is kept below or above a characteristic level, is believed to be a critical factor in the development of the TFAT as a fast sensing, miniature pressure sensor or a switching device. The work contained here reveals that the over-all response is the combined effect of three main factors: (a) the piezoelectricity of CdSe; (b) the strain dependence of the conductivity of the CdSe film alone; and (c) the presence of traps and donor states at the semiconductor-insulator interface and inside the insulator. In the inverted structure of the device discussed here, (a) and (b) are shown to act in opposition and therefore the device performance is modified according to their relative magnitudes. Piezoelectricity is shown to be the principal mechanism when the device is operated at a gate voltage V_g above the flat band voltage V_FB. The strain dependence of V_FB and its value are obtained by following a simple curve-fittinh procedure of the data relating the transconductance g_m to V_g. Three possible mechanisms for (b), namely piezoresistivity, band gap change and carrier mobility modulation based on Petritz's polycrystalline model, are discussed.