CdSe/ZnS核-壳结构量子点的非线性光学吸收

利用开孔Z扫描技术研究了吸收峰分别为553 nm和503 nm的两种尺寸CdSe/ZnS核-壳结构量子点溶液的非线性吸收性质.对于532 nm,6 ns激光脉冲,两种材料均表现出饱和吸收向反饱和吸收转化的现象.数值模拟结果表明：当吸收峰波长大于激光波长时,饱和吸收过程由快、慢两种机制组成,分别对应基态载流子被激发至不同的激发态,而强光下的反饱和吸收与快过程相关;当吸收峰波长小于激光波长时,饱和吸收主要由快过程机制引起,强光下的反饱和吸收源自激发态吸收和双光子吸收.我们的研究结果表明半导体量子点是研制光开关和光限制器件的理想候选材料.     

纳米银增强聚合物太阳能电池光吸收的研究

基于共轭聚合物给体材料P3HT和富勒烯衍生物受体材料PCBM共混的体异质结结构 的聚合物太阳能电池因其空穴载流子迁移率低而限制了P3HT:PCBM功能层厚度, 从而影响了器件对入射光的吸收. 在聚合物功能层内引入金属纳米颗粒可以利用金属表面等离子体效应增强器件内电场并改善器件的光吸收. 本文基于时域有限差分法(finite difference time domain, FDTD)方法模拟得到了聚合物功能层内包含了直径为50 nm纳米银球并且球间距为50 nm的聚合物太阳能 电池器件在波长分别为400 nm和500 nm照射时的二维光电场分布以及入射角分别为15°, 45°, 60°时包覆纳米银聚合物功能层横截面内的光电场强度分布; 计算得到了银纳米颗粒尺寸分别为10 nm, 20 nm和50 nm时以及分布在空穴传输层PEDOT:PSS的纳米银器件的光吸收; 并计算了斜入射时包覆纳米银的聚合物功能层光吸收. 理论分析表明: 聚合物功能层加入纳米银球后, 因为纳米银球的表面等离子体效应使入射光在功能层内散射增强而使器件内的光电场重新分布; 直径较大的纳米银颗粒能产生大角度的光散射, 更有利于聚合物功能层对光的吸收. 这里, 基于有机银盐还原法制备了纳米银颗粒并制备了银等离子体增强的聚合物太阳能电池, 其结构为: glass/ITO (～100 nm)/PEDOT:PSS (40 nm)/P3HT:PCBM (～100 nm)(nano-Ag)/LiF (1 nm)/Al (120 nm). 该器件与平板器件的性能对比实验证实: 通过在聚合物功能层内上引入纳米银颗粒可以有 效增加器件光吸收并改善器件电学性能, 器件外量子效率在520 nm处最大增加了17.9%. 关键词： 纳米银 表面等离子体共振 时域有限差分 聚合物太阳能电池     

Numerical study of metamaterial absorber and extending absorbance bandwidth based on multi-square patches

A simple design of metamaterial absorber (MA) was proposed based on a periodic array of metal patch at microwave frequencies. Our design could exhibit absorption of 99.9% confirmed by numerical simulation. Such high narrowband absorption which mainly based on strong electric and magnetic resonances overlapping in a certain frequency range and perfect impedance-matched (z = 1) to the free space. Numerical simulations demonstrate that the MA could achieve very high absorptivity at wide angles of incidence for both transverse electric (TE) wave and transverse magnetic (TM) wave. The absorption band of our device is effectively extended by patterning multi-square patches of different dimension elements with appropriate geometrical parameters in a co-planar. Finally, the composite MA is only 0.4 mm thick, with a maximum absorption of 99.8% at 15.8 GHz, and a full width at half maximum (FWHM) bandwidth of 2 GHz by numerical simulation, which may have potential applications in the detection of explosives and stealth.     

Characterization of SnO2/Pb2CrO5 thin film/metal photovoltaic device

The photovoltaic behavior in a design of SnO₂/Pb₂CrO₅ thin film/metal (Au or Al) is described as functions of light intensity and wavelength for two different illumination directions. The Pb₂CrO₅ thin film in each device is formed over the SnO₂ coated glass substrate by an electron-beam evaporation technique. When illuminated from the metal side, the device with Au or Al shows the positive or the negative photovoltage, respectively. For the illumination from the SnO₂ side, the device with Au has the negative photovoltage at the short wavelength, and the positive one at the longer, while the device with Al has the negative photovoltage at both wavelength regions. These photovoltaic devices have two junctions at both sides of the Pb₂CrO₅ thin film. The band model of each device is also discussed.     

Enhancing light absorption for organic solar cells using front ITO nanograting and back ultrathin Al layer

To address the discrepancy between carrier collection and light absorption of organic solar cells caused by the limited carrier mobility and optical absorption coefficient for the normally employed organic photoactive layers, a light management structure composed of a front indium tin oxide(ITO) nanograting and ultrathin Al layer inserted in between the photoactive layer and the electron transport layer(ETL) is introduced. Owing to the antireflection and light scattering induced by the ITO nanograting and the suppression of light absorption in the ETL by the inserted Al layer, the light absorption of the photoactive layer is significantly enhanced in a spectral range from 400 nm to 650 nm that also covers the main energy region of solar irradiation for the normally employed active materials such as the P3HT:PC_(61) BM blend. The simulation results indicate that comparing with the control device with a planar configuration of ITO/PEDOT:PSS/P3HT:PC_(61) BM(80-nm thick)/Zn O/Al, the short-circuit current density and power conversion efficiency of the optimized light management structure can be improved by 32.86% and 34.46%. Moreover, good omnidirectional light management is observed for the proposed device structure. Owing to the fact that the light management structure possesses the simple structure and excellent performance, the exploration of such a structure can be believed to be significant in fabricating the thin film-based optoelectronic devices.     

氮化铌纳米线光学特性

氮化铌(NbN)纳米线是超导纳米线单光子探测器(SNSPD)常用的光敏材料,其光学性质是影响SNSPD性能的关键因素.本文结合实验数据和仿真结果,系统研究了多种NbN超导纳米线探测器器件结构的光学特性,表征了以下四种器件结构下的反射光谱以及透射光谱:1)双面热氧化硅衬底背面对光结构;2)双面SiN硅衬底背面对光结构;3)硅衬底上以金层+SiN缓冲层为反射镜的正面对光结构;4)以分布式布拉格反射镜(DBR)为衬底的正面对光结构.并在上述四种器件结构基础上,生长了不同厚度的NbN薄膜,观察不同厚度NbN薄膜的吸收效率.经分析,发现在不同器件结构下的最佳NbN厚度与光吸收率的关系如下:双面热氧化硅衬底上的NbN层在1606 nm处最大吸收率为91.7%,其余结构在最佳NbN厚度条件下吸收率都能达到99%以上.其中双面SiN的硅衬底结构中最大吸收率为99.3%, Au+SiN为99.8%, DBR为99.9%.最后,将DBR器件实测结果与仿真结果进行了差异性分析.这些结果对高效率SNSPD设计与研制具有指导意义.     

CuI/Al双层电极的有机场效应晶体管

制备了CuI/Al为源极和漏电极的并五苯基场效应晶体管.相对于纯金属(Al, Au)电极的晶体管,所研制的晶体管的迁移率、阈值电压VT、开关电流比I_on/I_off等参数都有明显改善.研究发现,在Al电极与并五苯半导体之间引入CuI作为空穴注入层,能够明显降低Al电极与并五苯之间的空穴注入势垒.紫外-可见光谱和X射线光电子能谱数据表明,这种空穴注入势垒的降低源自并五苯和Al向CuI的电子转移. 关键词： 有机场效应晶体管 CuI/Al双层源漏电极 电子转移     

Bathocuproine/Ag复合电极对于聚合物光伏器件效率和稳定性的影响

采用Bathocuproine/Ag (BCP/Ag)复合电极代替Ca/Al复合电极, 制备PTB7:PC71BM 作为光敏层的聚合物光伏器件, 并通过改变BCP薄膜厚度来研究BCP/Ag复合电极对于器件光电转换器和稳定性的影响. 研究发现: 在光敏层和金属电极之间插入BCP修饰层后, 器件性能得到了显著的改善, 在BCP厚度为5 nm时, 器件的效率达到了6.82%, 且略高于Ca/Al复合电极的器件效率; 相比于采用Ca/Al复合电极的器件, BCP/Ag复合电极增大了器件的短路电流和外量子效率, 使器件效率得到提高; 同时器件的稳定性得到了显著的改善, BCP/Ag 复合电极器件的衰减速率几乎和未插入BCP的器件衰减速率相同, 相对于Ca/Al复合电极器件大幅提高.     

Efficient single-frequency fiber lasers with novel photosensitive Er/Yb optical fibers

Boron- and germanium-doped highly photosensitive cladding is used in a novel design to achieve photosensitive Er/Yb-doped fibers, permitting short, strong gratings (length ~1 cm, reflectivity >99%) to be written without hydrogenation. The high absorption at 980 nm in Er/Yb fibers permits efficient pump absorption over a short device length, which is ideal for achieving highly efficient single-frequency fiber lasers. Both single-frequency Bragg-grating reflector and distributed-feedback lasers with slope efficiencies of 25% with respect to launched pump power have been realized in such fibers.     

入射角对Al0.5Ga0.5As-AlAs分布布拉格反射器反射光谱的影响

采用传输矩阵法对Al0.5Ga0.5As-AlAs材料的发光二极管分布布拉格反射器进行入射角的反射光谱研究,计算发现反射偏振光p和s随入射角的增大呈“V”形变化,在49.8°处有最小反射值。不同入射介质[以空气和限制层(Al0.7Ga0.3)0.5In0.5P材料]下的反射光谱受入射角的影响差异很大,其中入射角对空气入射介质的反射谱影响较小,由0°入射的反射率88.13%降至45°的84.94%,反射峰值波长蓝移仅10 nm;但入射角对(Al0.7Ga0.3)0.5In0.5P入射介质的反射谱影响很大,仅从0°到45°入射,反射率降幅就超过45%,反射峰值波长蓝移超过127 nm。为了减缓这种影响,提出了多波长布拉格反射器结构设计。计算表明多波长分布布拉格反射器在0ο~45°的入射角内比传统的分布布拉格反射器有更好的光谱特性,这对提高发光二极管的出光效率有现实意义。     

利用不同阴极缓冲层来改善Pentacene/C60太阳能电池的性能

制备了结构为ITO/Pentacene/C₆₀/Al的双层光伏电池器件,在C₆₀/Al界面插入了常用的缓冲层材料bathocuproine(BCP)作为阴极缓冲层,通过优化BCP层的厚度来提高电池的性能并研究了阴极缓冲层的作用机理.实验发现,BCP厚度为10 nm时器件的效率最高,为0.46%.在此基础上,利用bathophenanthroline(Bphen)和3,4,9,10-Perylenetetracarb-oxylicdianhydride(PTCDA 关键词： 有机太阳能电池 Pentacene 60')" href="#">C₆₀ 缓冲层     

Janus Device Based on Liquid Crystal Regulation with a Large Incidence Angle: Analogous Quantum Optical Effect and Absorption

In this paper, a Janus metastructure device (JMD) is proposed. The JMD design introduces asymmetric structures, which leads to the generation of analogous quantum optical effects when light is incident at large angles. Specifically, forward electromagnetic-induced transparency (EIT) and backward narrowband absorption (NA) are achieved when light is incident along different directions, displaying Janus characteristics in the forward and backward directions. Additionally, the operating frequency of JMD can be controlled through the use of liquid crystal. Such features hold promising potential for various applications in photonic and optoelectronic fields. When the axial direction of the liquid crystal is oriented along the x-direction, the JMD achieves a transparent window over 90% within 0.46–0.51 THz at forward incidence, and an absorption peak of 84.1% appears at 0.331 THz at backward incidence. When the axial direction is oriented along the y-direction, the JMD achieves EIT in the range of 0.51–0.575 THz at forward incidence, and a backward absorption peak of 93.3% occurs at 0.305 THz. In addition, the performance changes at different polarization and incidence angles are presented. The mechanism of absorption generation, the method of suppressing excess absorption, and the parametric inversion of the electromagnetic characteristics of JMD are also discussed.     

Nanosilver surface plasmon response enhanced the photovoltaic performance of organic solar cells

Nanosilver island thin films with different thickness were synthesized by vacuum vapor deposition between ITO and PEDOT:PSS for organic solar cells, forming the structure of ITO/AgNPs layer/PEDOT:PSS/P3HT:PCBM/LiF/Al. Surface morphology and UV–vis absorption spectrum were investigated by AFM and UV–vis scanning spectrophotometer. It was found that after adding the nanosilver film, the optical properties of the device were enhanced with increasing the thickness of nanosilver island films. When the thickness of nanosilver thin films is 3.0 nm, the most significant surface plasmon response and red-shift of the resonance absorption peak appeared. Meanwhile, short circuit current density of the device increased from 9.93 mA/cm² to 12.98 mA/cm², the fill factor increased from 49.35% to 52.79% and the power conversion efficiency increased from 3.05% to 4.01%. These results provided a theoretical guidance to optimize the design and increase the performance of solar cells.     

多层有机薄膜电致发光器件

制备了以苯乙烯锘三苯胺衍生物为空穴传输层Ａｌｑ３为发光层的双层有机薄膜电致姨光器件。还把不同厚度的恶二唑衍生物加在ＳＡ和Ａｌｑ３之间制备了两种三层结构的有机薄膜电致发光器件，实现了ＳＡ的蓝色发光。进行了器件存放实验，发现了器件在大气中有较好的稳定性。     

基于树枝结构单元的超材料宽带微波吸收器

本文设计并制作了一种基于树枝结构单元的超材料宽带微波吸收器.该超材料吸收器采用夹层结构,由按六边形密集排布的金属树枝阵列、双层介质基板和金属薄膜组成.通过调节树枝单元的几何参数和金属树枝阵列的排布方式,可以出现三个吸收峰,实现三频工作.通过调节三个吸收峰工作的频率形成宽频吸收,采用夹层结构提高吸收效率,从而对垂直入射到超材料表面的微波实现高吸收.实验表明吸收器的反射曲线从9.79 GHz到11.72 GHz出现了反射率小于10%的较宽吸收带,透射曲线恒等于0,吸收率大于90%的带宽为1.93 GHz.这种 关键词： 树枝状结构 夹层结构 吸收效率 吸收带宽     

多维漫透射光谱提高复杂混合溶液分析能力

多维漫透射光谱技术利用传统的近红外透射测量方式,增加一维扫描装置,获得透射方向上的径向光谱,并利用多点漫透射光谱对复杂混合溶液进行成分分析。实验设计了基于氙灯光源、精密电控平移台和光谱仪的检测装置,选用Intralipid-20%,India Ink和C₆H₁₂O₆共配制225种成分含量不同的混合溶液,分别测量距其透射中心点0～5 mm(间隔0.25 mm)范围内的20点漫透射光谱信号,以偏最小二乘回归算法对单点和多点漫透射光谱信号进行建模分析。实验得到India Ink含量和Intralipid-20%含量随漫透射光位置点的增加建模及预测的精度提高,C₆H₁₂O₆含量随漫透射光位置点的增加建模及预测精度没有明显变化。结果表明,增加不同位置信息的漫透射光谱信号,能够提高复杂混合溶液中强吸收物质和强散射物质的信噪比,对于弱吸收弱散射物质有望在提升系统精度的前提下提高其预测能力。     

基于表面等离子体共振增强的硅基锗金属-半导体-金属光电探测器的设计研究

金属-半导体-金属光电探测器的光栅结构可激发表面等离子体, 有效增强探测器的吸收. 为深入研究器件结构对于表面等离子体的激发及共振增强的影响, 本文提出了一种具有超薄有源层的硅基锗金属-半导体-金属光电探测器的设计方法. 采用时域有限差分的方法详细分析了光栅周期、光栅厚度、 光栅间距及有源层厚度对于表面等离子体共振增强器件性能的影响, 通过仿真模拟获得了器件的最佳结构, 详细地分析了各个界面激发的表面等离子体及其共振模式对于光谱吸收增强的机理. 仿真结果表明, 有源层锗的厚度为400nm的超薄器件在通信波段具有较高的吸收, 尤其在1550nm波长处器件的归一化的光谱吸收率可以高达53.77%, 增强因子达7.22倍. 利用共振效应能够极大地提高高速器件的光电响应, 为解决光电探测器响应度与响应速度之间的相互制约关系提供了有效途径. 关键词： 表面等离子体 锗探测器 时域有限差分仿真     

A multi-band and polarization-independent perfect absorber based on Dirac semimetals circles and semi-ellipses array

We design a four-band terahertz metamaterial absorber that relied on the block Dirac semi-metal(BDS). It is composed of a Dirac material layer, a gold reflecting layer, and a photonic crystal slab(PCS) medium layer. This structure achieved perfect absorption of over 97% at 4.06 THz, 6.15 THz, and 8.16 THz. The high absorption can be explained by the localized surface plasmon resonance(LSPR). And this conclusion can be proved by the detailed design of the surface structure. Moreover, the resonant frequency of the device can be dynamically tuned by changing the Fermi energy of the BDS. Due to the advantages such as high absorption, adjustable resonance, and anti-interference of incident angle and polarization mode, the Dirac semi-metal perfect absorber(DSPA) has great potential value in fields such as biochemical sensing, information communication, and nondestructive detection.     

苯甲酰水杨酸铽的合成与发光特性研究

合成了一类以苯甲酰水杨酸(Benzoyl Salicylic Acid,BSA)为配体的稀土铽配合物,将导电高分子材料PVK引入到配合物中,制成了结构为ITO／PVK：Tb(BSA)4／LiF／Al的电致发光器件。并对该配合物的吸收特性及电致发光和光致发光性能进行了研究,实验数据表明,在PVK与Tb(BSA)4之间存在着能量传递,在电致发光中,PVK的发光完全被抑制,这与光致发光的表现不同,这是由于两种发光(光致和电致)机理不同造成的。章同时比较了几种不同PVK掺杂浓度对于器件性能的影响。     

氧化锌掺铝绒面薄膜在有机光伏电池中的应用

目前有机光伏电池的吸光活性层电学传输特性和光学吸收特性的不匹配是制约其能量转换效率提升的主要原因之一. 通过陷光结构对入射光进行调控, 提高电池对光的约束和俘获能力从而达到“电学薄”和“光学厚”的等效作用, 是解 决有机光伏电池电学和光学不匹配的有效手段. 本文采用湿法刻蚀技术获得了系列时间梯度的绒面氧化锌掺铝薄膜, 并将其作为有机光伏电池的入射陷光电极, 显著增强了电池的光学吸收. 研究发现, 当使用浓度0.5%的稀HCL腐蚀30 s后的氧化锌掺铝薄膜作为入射电极后, 电池的光电性能和效率显著增强. 基于此绒面电极电池的电流密度比平面结构的电池提高了8.17%, 效率改善了11.29%. 通过对绒面电极表面的修饰处理, 实现了电极与光活性层之间良好的界面接触, 从而减小了对电池的开路电压和填充因子的影响.