金膜上CsPbBr3纳米晶超晶格增强双光子发射特性研究

钙钛矿微纳结构双光子荧光在高分辨成像、光电转换等领域应用广泛,其中增强双光子荧光发射强度是提高器件性能的关键。与电介质基底相比,置于贵金属薄膜上的微纳结构由于等离激元的激发作用,能够有效增强线性及非线性光学响应。基于此,提出了在金膜上自组装CsPbBr₃纳米晶超晶格结构,与玻璃基底上样品相比,金膜上超晶格结构内部形成了更强的局域场增强。实验结果表明,其线性光致发光强度提高了约100%,而双光子发光强度得到了约16倍的显著提升。进一步通过改变泵浦光偏振方向可见,这种超晶格的双光子发射具有偏振依赖性,偏振角度在0°~360°范围内呈现四重对称性。研究结果表明,金膜上CsPbBr₃纳米晶超晶格是一种有效增强双光子发射的体系,这为构建高性能微纳非线性光子器件提供了新的可能性和优化思路。     

双层复合纳米森林结构的制备及其宽光谱高吸收光学特性研究

基于等离子体再聚合技术制备了纳米纤维—纳米锥双层森林结构,并通过磁控溅射工艺在结构表面引入金属纳米颗粒实现了双层复合纳米森林结构,工艺流程简单便捷,与常规微纳加工工艺兼容性好,易于实现大面积的并行加工.将纳米森林的陷光效应和金属纳米颗粒的表面等离激元效应相结合,对双层复合纳米森林结构的光吸收特性进行深入研究与探索,最终实现了该复合纳米森林结构在1.5~25μm波长范围内84.1%的平均吸收率.具有宽光谱高吸收光学特性的双层复合纳米森林结构有望在提高红外器件性能和拓展器件应用等方面获得广泛应用.     

等离激元纳米海胆结构增强热载流子的产生与注入

等离激元激发产生的热载流子可以有效驱动化学反应的发生,进而实现太阳能的高效利用。合理设计等离激元金属纳米结构是提高热载流子产生与注入效率,进而实现超宽光谱吸收和高效能量转换的有效途径。本课题组制备了具有高密度尖端的等离激元纳米海胆颗粒,并构建了金属半导体复合结构的光阳极,通过测试光阳极微反应区的光电流响应评估了热载流子的产生与注入效率。结果表明：纳米海胆结构具有优异的光电催化活性,其尖端处的大量热点促进了热载流子的产生,金属与半导体间丰富的界面接触增加了热载流子的注入机会。该设计为热载流子的高效激发与提取提供了参考。     

表面等离激元纳米结构增效的光电探测器进展（特邀）

光电探测器作为航空航天、深空探测和环境监测等领域的核心器件之一,具有重要的科学研究和实用价值。表面等离激元具有可突破光学衍射极限、实现纳米聚焦的性质,为光电探测器的性能提升提供了全新的技术手段,是近年来光电探测增效研究领域的热点之一。文中围绕表面等离激元纳米结构增效的光电探测器研究展开综述,首先介绍了各类表面等离激元纳米结构的物理特性,主要包括局域表面等离激元结构和传导型的表面等离极化激元结构,以及由表面等离激元金属和半导体材料构成的异质结构;然后重点从探测器性能、探测原理和工艺方法等角度,介绍了等离激元纳米结构增强的光电探测器的研究进展;最后对表面等离激元纳米结构增效的光电探测器及其在未来面临的挑战进行了总结和展望。     

银纳米线-三角片耦合结构发射光的偏振依赖特性

银纳米线可以承载传播的表面等离激元,纳米片可以产生局域的表面等离激元,二者形成的耦合结构不但可以将传播光场耦合为局域增强光场,还可以调控光场的偏振态等性质,为纳米光调控提供新的自由度。本团队构建了银纳米线-三角片耦合结构,并发现耦合结构的发射偏振与纳米线-三角片的耦合方式有关：当三角片与纳米线之间是“线”接触耦合时,耦合结构的发射偏振随着激发偏振的旋转而旋转;当二者是“点”接触耦合时,无论激发偏振如何变化,发射偏振角度几乎保持160°不变。进一步,利用时域有限差分法验证了出射偏振对入射偏振的依赖特性。通过计算自由电流密度体积分揭示了纳米线中传播的表面等离激元模式与银纳米线-三角片耦合模式的转化机制,以及不同表面等离激元模式的叠加对发射偏振的调控。这些发现为纳米尺度上的光调控以及在纳米尺度上构建纳米光子器件提供了更多灵活性。     

油性金属-半导体异质结构可见光催化 特性及在水处理中的应用研究

利用金属等离激元热电子效应,使突破半导体带隙宽度限制的可见光催化成为可能,是有机污染物处理方面的新兴方向。首先制备了油性Ag-TiO2纳米棒异质结构,研究了其光谱特性及催化过程中热电子转换机制,验证了在可见光下对水中有机染料的高效催化分解能力。结果表明,相比于TiO2纳米棒,Ag-TiO2纳米棒异质结构展现出显著的催化能力,罗丹明B的分解速率提高了近三倍,这种催化材料高效、环保,在水中不残留,在水处理等领域具有广泛的应用前景。     

复合结构的等离激元模式耦合关系及光学特性研究

提出一种以Au为材料的正方形框和中空圆柱嵌套的亚波长周期性复合结构,采用时域有限差分算法对复合结构进行数值模拟研究.研究发现,波长在400～900 nm的线偏振平面波垂直入射情况下,最小的透过率能达到7.46％,最小的半峰全宽能达到7.25 nm,最大的反射率为87.61％,最大吸收率达到38.00％,且表现出透射光谱...     

基于非铅钙钛矿Cs3Cu2I5闪烁体的X射线成像研究

最近报道的卤化物钙钛矿具有光致发光量子产率高、发射带窄的特性,可作为一种新 型X 射线探测材料,但仍存在光和热稳定性低、铅毒性等问题。本文研究一种低温溶液法 制备的无机非铅钙钛矿Cs₃Cu₂I₅纳米晶材料,分析其在X射线辐射下的发光特性, 并探究 不同厚度Cs₃Cu₂I₅纳米晶材料的转换效率与X 射线源管电压之间的关系。在成像实 验中, 本文设计一种高效的Cs₃Cu₂I₅材料闪烁体转换屏,研制基于Cs₃Cu₂I₅材料闪烁 体转换屏的X 射线成像系统,分别对剃须刀刀片和蜗牛壳进行X射线成像。实验结果表明:在X射线辐 射下钙钛矿Cs₃Cu₂I₅的发射峰在波长为460 nm时达到峰值;在 厚度为0.30 mm 时, Cs₃Cu₂I₅材料转换效率较高;成像结果显示图像轮廓清晰、物体内部结构层次分明 。研究 表明:非铅钙钛矿Cs₃Cu₂I₅纳米晶材料可以作为一种新型闪烁体,在X射线探测与成 像 方面有着巨大的应用潜力。     

双蝶形金属纳米光天线的远场特性研究

为了提高对远场方向性调控的灵活性,提出双蝶形银纳米光天线,基于时域有限差分的方法研究了天线不同结构与尺寸的变化对远场方向性产生的影响。研究发现,由于局域表面等离激元的存在,偶极子源垂直放置于双蝶形银结构下表面一定距离时,远场方向图出现明显的旁瓣。天线长度的增加是方向图出现旁瓣的关键因素。天线臂之间夹缝的减小,使远场方向图中旁瓣增大,同时主瓣增益增大。天线厚度的增加使远场方向图出现旁瓣,主瓣增益先增大后减小。结果表明,双蝶形银纳米光天线能够改变与其相耦合的偶极子源的辐射方向性。     

Enhancement of photodetection based on perovskite/MoS2 hybrid thin film transistor

Perovskite/MoS₂ hybrid thin film transistor photodetectors consist of few-layered MoS₂ and CH₃NH₃PbI₃ film with various thickness prepared by two-step vacuum deposition. By implementing perovskite CH₃NH₃PbI₃ film onto the MoS₂ flake, the perovskite/MoS₂ hybrid photodetector exhibited a photoresponsivity of 10⁴A/W and fast response time of about 40 ms. Improvement of photodetection performance is attributed to the balance between light absorption in the perovskite layer and an effective transfer of photogenerated carriers from perovskite entering the MoS₂ channel. This work may provide guidance to develop high-performance hybrid structure optoelectronic devices.     

Growth and structure of wide-gap insulator films on SrTiO3

Wide-gap insulator films, CaZrO₃, CaHfO₃, LaGaO₃, and NdGaO₃, were grown on SrTiO₃(1 0 0) substrates with the aim of obtaining a gate insulator for epitaxial oxide devices. We show that CaZrO₃ and CaHfO₃ films were epitaxial and had a multi-domain in-plane structure due to their highly distorted perovskite structure. Most of the LaGaO₃ and NdGaO₃ films were polycrystalline, and therefore showed relatively high leak currents. CaHfO₃ had the best crystallinity among these four materials.     

High-Performance barium titanate capacitors with double layer structure

High-performance barium titanate (B_aTiO₃) capacitors with excellent electrical and dielectric properties have been made by a two step deposition scheme using reactive rf magnetron sputtering. A novel double layer structure has been developed to reduce the pinholes and improve the electrical properties, such as higher dielectric constant, lower dissipation factor, higher breakdown fields and low leakage currents. Films deposited on a cooled substrate are amorphous whereas those deposited on a heated substrate are poly crystalline. Both polycrystalline and amorphous natures are verified by x-ray diffraction and scanning electron microscopy. Amorphous films have a low leakage current, a high breakdown voltage up to 2.5 x 10⁶ V/cm, and a dielectric constant less than 20. Polycrystalline films yield a high dielectric constant of 330. However, these films also have large leakage currents. The capacitors with the two layer structures,i.e. amorphous layer on top of polycrystal layer, have been shown to be much superior to those prepared by either polycrystal or amorphous layer alone for practical applications. The dielectric constant and breakdown voltage of capacitors with a double layer are found to be as high as 220 and 1.2 x 10⁶ V/cm, respectively. The leakage current is reduced to the same order as the amorphous films alone.     

Copolymers based on thiazolothiazole-dithienosilole as hole-transporting materials for high efficient perovskite solar cells

The interlayers, including hole transporting layer (HTL) and electron transporting layer (ETL), segregating photoactive layer and the electrodes play an important role in charge extraction and transportation in perovskite solar cells (pero-SCs). Two novel copolymers, PDTSTTz and PDTSTTz-4, for the first time were applied as HTL in the n-i-p type pero-SCs, with the device structure of ITO/compact TiO₂/CH₃NH₃PbI_3-xCl_x/HTL/MoO₃/Ag. The highest occupied molecular orbitals (HOMO) levels of PDTSTTz and PDTSTTz-4 exhibit a suitable band alignment with the valence band edge of the perovskite. Both of them lead to improved device performances compared with reference pero-SCs based on P3HT as HTL. To further balance the charge extraction and the diffusion length of charge carriers, pristine C₆₀ was introduced at the cathode side of the pero-SCs, working together with TiO₂ as ETL. With insertion of both the HTL and ETL, the performance of pero-SCs was greatly enhanced. The optimized devices exhibited impressive PCEs of 14.4% and 15.8% for devices based on PDTSTTz and PDTSTTz-4. The improved performance is attributed to better light harvest ability, decreased interface resistance and faster decay time due to the introduction of the interlayers.     

Electrical aspects of photovoltaic devices based on bi-layer organic semiconducting materials

Here we have investigated the opto-electrical properties of bi-layer sandwich devices based on polymer/C₆₀ hetero junctions. In this type of device the polymer acts as an electron donor to the second layers the C₆₀ which plays the role of an electron acceptor.     

Excellent performance of gas sensor based on In2O3-Fe2O3 nanotubes

In₂O₃-Fe₂O₃ nanotubes are synthesized by an electrospinning method. The as-synthesized materials are characterized by scanning electron microscope and X-ray powder diffraction. The gas sensing results show that In₂O₃-Fe₂O₃ nanotubes exhibit excellent sensing properties to acetone and formaldehyde at different operating temperatures. The responses of gas sensors based on In₂O₃-Fe₂O₃ nanotubes to 100 ppm acetone and 100 ppm formaldehyde are 25 (240℃) and 15 (260℃), and the response/recovery times are 3/7 s and 4/7 s, respectively. The responses of In₂O₃-Fe₂O₃ nanotubes to 1 ppm acetone (240℃) and formaldehyde (260℃) are 3.5 and 1.8, respectively. Moreover, the gas sensor based on In₂O₃-Fe₂O₃ nanotubes also possesses an excellent selectivity to acetone and formaldehyde.     

Transport properties of thermoelectric materials for coolers

The Seebeck coefficient, thermal conductivity, electrical conductivity and Hall coefficient of cooler grade, p-and n-type ternary alloys of Bi₂Te₃-Sb₂Te₃-Sb₂Se₃ were measured between 10 and 300 K. Between 300 K and about 150 K the temperature dependence of the transport properties can be explained by assuming nondegeneracy and a lattice scattering mechanism. The difference between the temperature dependence of the Hall effect in n-and p-type alloys can be explained by the presence of sub-bands of light and heavy holes in the valence band of p-type alloys.     

介稳态TiCl4醇水溶液水解制备TiO2致密层及其在无机-有机杂化异质结钙钛矿太阳电池中的应用

致密层作为钙钛矿太阳电池的重要组成部分, 对其制备方法, 工艺及微结构等性质的研究对提高钙钛矿太阳电池的光伏性能具有重要影响. 本文利用介稳态的TiCl₄醇水溶液作为前驱体溶液, 通过旋涂水解制备TiO₂致密层, 并研究了前驱体溶液不同醇水比对致密层微结构及其相应太阳电池光伏性能的影响. 结果表明, 将2 mol.L_-1的TiCl₄的水溶液按醇水体积比3:1的比例用异丙醇稀释后所制备的TiO₂致密层其厚度为126 nm, 且相应的太阳电池取得最高的光电转换效率10.6 %.     

基于富勒烯类材料太阳能电池研究进展

从太阳能电池基本原理、新材料合成、活性层和修饰层的工艺改进、器件结构多样化以及电极材料的选取及工艺等方面介绍了基于富勒烯类材料的有机太阳能电池的研究进展,并探讨了今后有机薄膜器件研究的发展趋势。