多特征融合的鸟类物种识别方法

针对短时窗平均/长时窗平均算法从次声台站监测数据中提取的信号仍然包含噪声的问题,对支持向量机和人工神经网络的机器学习方法进行了研究。采用小波包分解的方法对信号进行重构,提取出各频带内的重构信号能量特征,对事件信号和噪声进行了识别实验,并分析了提高识别能力的方法,为工程应用提供理论参考。实验结果表明,在训练数据集不大的情况下,通过优化模型结构可以将两种方法的识别能力提高到可以接受的水平。     

Control of Charge Transport in the Perovskite CH3NH3PbI3 Thin Film

Carrier density and transport properties in the CH₃NH₃PbI₃ thin film have been investigated. It is found that the carrier density, the depletion field, and the charge collection and transport properties in the CH₃NH₃PbI₃ absorber film can be controlled effectively by different concentrations of reactants. That is, the carrier properties and the self‐doping characteristics in CH₃NH₃PbI₃ films are strongly influenced by the reaction thermodynamic and kinetic processes. Furthermore, by employing mixed solvents with ethanol and isopropanol to deposit the CH₃NH₃PbI₃ film, the charge collection and transport efficiencies are improved significantly, thereby yielding an overall enhanced cell performance.     

The Effect of Humidity upon the Crystallization Process of Two‐Step Spin‐Coated Organic–Inorganic Perovskites

Moisture is shown to activate the reaction between PbI₂ and methylammonium halides. In addition, two activating mechanisms are proposed for the formation of CH₃NH₃PbI₃ and CH₃NH₃PbI_3?xCl_x films from a series of carefully controlled experiments. When these rapidly formed perovskite films are directly fabricated into the devices, poor photovoltaic properties are found, due to heavy surface charge recombination. However, the cell performance can be significantly enhanced to 13.63 % and to over 12 % in the steady state for CH₃NH₃PbI₃ and to 15.50 % and over 14 % in the steady state for CH₃NH₃PbI_3?xCl_x, if the rapidly formed perovskite film is annealed. Thus, it is believed that moisture (below 60 % RH) is not a problem for the fabrication of highly efficient perovskite solar cells.     

两步互扩散法制备高性能CsPbCl3薄膜紫外光电探测器

紫外光电探测器无论在军用和民用上都有着巨大的应用前景,CsPbCl₃作为钙钛矿家族中形成能最大,化学性能稳定的成员,在可见光盲区的紫外光电探测器中有着很大潜在的应用价值。本文针对CsPbCl₃薄膜难以制备的问题,发展了一种两步互扩散溶液法,通过控制前驱体PbCl2的形貌,成功地制备了CsPbCl₃薄膜。利用扫描电镜、吸收光谱和X射线表征技术,证实了制备出的薄膜表面平整无孔洞、晶粒饱满和吸光度强。通过瞬态荧光和变激发光强的稳态荧光,揭示了薄膜具有载流子寿命长、缺陷态少等优异性能。最终构建出了响应度为0.75 A·W^?1的横向结构紫外光电探测器,为将来进一步发展高性能CsPbCl₃薄膜紫外光电探测器奠定了基础。     

多孔TiO2层厚度对钙钛矿太阳能电池性能的影响

制备了基于不同厚度(100～500 nm)多孔TiO₂层的钙钛矿太阳能电池, 并用SEM、XRD、紫外-可见吸收谱、电压-电流曲线、电化学阻抗谱进行了表征. 研究发现, 多孔TiO₂薄膜厚度对电池性能有很大影响, 即随着多孔TiO₂薄膜厚度的增加, 短路电流略有提高, 而开路电压和填充因子呈下降趋势;但同时, 较厚的多孔TiO₂薄膜可有效减弱滞回现象. 进一步采用电化学阻抗谱和暗态电流-电压曲线研究了载流子复合. 电化学阻抗谱表明, 膜厚增加会增大载流子复合但不会改变二极管理想因子. 通过拟合暗态电流-电压曲线得到反向饱和电流, 随着膜厚增加, 反向饱和电流会增大, 从而加剧了载流子复合. 通过优化多孔TiO₂薄膜厚度, 基于150 nm多孔TiO₂薄膜钙钛矿电池的认证效率达到15.56%.     

Perovskite thin-film solar cell: excitation in photovoltaic science

As a new member of thin-film solar cells,the perovskite solar cells have inspired a new research hot in new photoelectric materials and devices,and have given a new energy to the photovoltaic science.Currently,various device structures,including mesoporous and planar,with and without hole transport material have been developed.In this review,much focus has been addressed to the deposition of high-quality perovskite films,structural optimization,and interface engineering as well as the understanding of the charge generation,transport,and recombination mechanisms of the devices.Furthermore,cost,stability,and environment issues of the cell are also discussed for commercial application.     

铜锌锡硫硒薄膜太阳能电池一价金属替位的研究进展

铜锌锡硫硒(CZTSSe)电池具有组成元素丰度高且环境友好、光吸收系数高、带隙可调、高稳定性等优点, 是一类非常有发展前景的新型薄膜太阳能电池. 目前, CZTSSe电池最高认证效率为12.6%, 与商品化铜铟镓硒(CIGS)电池相比仍然有较大差距, 特别是开路电压(V_OC)和填充因子(FF)偏低. 开压损耗是制约CZTSSe器件效率进一步提升的关键因素之一. 其中, 吸收层带尾态和深能级缺陷及界面能级不匹配是开压损耗大的主因, 而Cu-Zn无序引起的铜锌替位(Cu_Zn)与锌锡替位(Sn_Zn)缺陷又是影响带尾态的关键因素, 因此, 减少Cu_Zn和Sn_Zn缺陷有助于提升V_OC. 一价金属替位能有效改善带尾态、构建合适能带结构, 在一定程度上解决器件开压损耗问题. 但是, 有关一价金属替位如何影响CZTSSe电池性能, 仍然缺乏全面系统的概述. 本文综述了基于一价金属替位方法CZTSSe电池的研究进展. 首先介绍CZTSSe电池的发展历程、工作原理、制备工艺和关键材料等; 其次, 详细讨论一价金属替位的理论研究; 再次, 结合实验进展, 重点讨论一价金属部分替位及完全替位CZTSSe材料的制备及其对带尾态、界面缺陷和能带结构研究; 最后, 对一价金属替位研究的关键科学问题、未来发展潜力等进行讨论和展望, 并提出可能的解决思路.     

Stability improvement under high efficiency—next stage development of perovskite solar cells

With efficiency of perovskite solar cells(PSCs) overpassing 23%, to realize their commercialization, the biggest challenge now is to boost the stability to the same level as conventional solar cells. Thus, tremendous effort has been directed over the past few years toward improving the stability of these cells. Various methods were used to improve the stability of bulk perovskites,including compositional engineering, interface adjustment, dimensional manipulation, crystal engineering, and grain boundary decoration. Diverse device configurations, carrier transporting layers, and counter electrodes are investigated. To compare the stability of PSCs and clarify the degradation mechanism, diverse characterization methods were developed. Overall stability of PSCs has become one central topic for the development of PSCs. In this review, we summarize the state-of-the-art progress on the improvement of device stability and discuss the directions for future research, hoping it provides an overview of the current status of the research on the stability of PSCs and guidelines for future research.