The current-voltage（I-V） characteristics of cBN crystal sandwiched between two metallic electrodes are measured and found to be nonlinear. Over 20 samples are measured at room temperature with various electrodes, an...The current-voltage（I-V） characteristics of cBN crystal sandwiched between two metallic electrodes are measured and found to be nonlinear. Over 20 samples are measured at room temperature with various electrodes, and the resulting curves are all similar in shape. When a voltage of about 560V is applied to the cBN crystal, the emitted light is visible to the naked eye in a dark room. We explain these phenomena by the space charge limited current and the electronic transition between the X and Г valleys of the conduction band.展开更多
Organic solar cells with inverted planar heterojunction structure based on subphthalocya- nine and C60 were fabricated using several kinds of materials as cathode buffer layer （CBL）, including tris-8-hydroxy-quinoli...Organic solar cells with inverted planar heterojunction structure based on subphthalocya- nine and C60 were fabricated using several kinds of materials as cathode buffer layer （CBL）, including tris-8-hydroxy-quinolinato aluminum （Alq3）, bathophenanthroline （Bphen）, bathocuproine, 2,3,8,9,14,15-hexakis-dodecyl-sulfanyl-5,6,11,12,17,18-hexaazatrinaphthylene （HATNA）, and an inorganic compound of Cs2CO3. The influence of the lowest unoccupied molecular orbital level and the electron mobility of organic CBL on the solar cells perfor- mance was compared. The results showed that Alq3, Bphen, and HATNA could significantly improve the device performance. The highest efficiency was obtained from device with an- nealed HATNA as CBL and increased for more than 7 times compared with device without CBL. Furthermore~ the simulation results with space charge-limited current theory indicated that the Schottky barrier at the organic/electrode interface in inverted OSC structure was reduced for 27% by inserting HATNA CBL.展开更多
To understand the complex behaviors of photogenerated charge carriers within polymer-based bulk-heterojunction-type solar cells,the charge-carrier photogeneration and extraction dynamics are simultaneously estimated u...To understand the complex behaviors of photogenerated charge carriers within polymer-based bulk-heterojunction-type solar cells,the charge-carrier photogeneration and extraction dynamics are simultaneously estimated using a transient photocurrent technique under various external-bias voltages,and a wide range of excitation intensities are analyzed.For this purpose,conventional devices with 80 nm thick active layers consisting of a blend of representative P3HT and PTB7 electron-donating polymers and proper electron-accepting fullerene derivatives were used.After the correction for the saturation behavior at a high excitation-intensity range nearby the regime of the space charge-limited current,the incident-photon-density-dependent maximum photocurrent densities at the initial peaks are discussed as the proportional measures of the charge-carrier-photogeneration facility.By comparing the total number of the extracted charge carriers to the total number of the incident photons and the number of the initially photogenerated charge carriers,the external quantum efficiencies as well as the extraction quantum efficiencies of the charge-carrier collection during a laser-pulse-induced transient photocurrent process were obtained.Subsequently,the charge-carrier concentration-dependent mobility values were obtained,and they are discussed in consideration of the additional influences of the charge-carrier losses from the device during the charge-carrier extraction that also affects the photocurrent-trace shape.展开更多
随着工程电介质领域研究的发展,诸多没有得到公认解释的问题逐渐出现,为此,本文提出了几个重要的问题及思考以供相关研究工作者参考。1994年Lewis首次提出了纳米电介质,2003年至今已成为工程电介质领域的研究热点,但从20余年该领域的研...随着工程电介质领域研究的发展,诸多没有得到公认解释的问题逐渐出现,为此,本文提出了几个重要的问题及思考以供相关研究工作者参考。1994年Lewis首次提出了纳米电介质,2003年至今已成为工程电介质领域的研究热点,但从20余年该领域的研究内容、作者的原意以及新近又提出的纳米结构电介质来看,我们认为应把名称改为纳米电介质复合物,并按照低维物理对纳米电介质作了重新定义。分析了Lewis与Tanaka界面的具体含义,提出了纳米高聚物复合物硬/软界面及其具有结构复杂性、不确定性与易变性的新概念,并剖析了硬、软表面的尺度及理化特性。提出了从A Einstein还原论、P W Anderson的层展现象与R P Feynmann的思维方法以启迪相关研究的新思维。从空间电荷限制电流(SCLC)存在条件的约束和高聚物或其复合物中由于自身结构的多层次性、复杂界面、电极接触以及共存的电子与离子电导等因素的严重影响,提出了从欧姆区过渡到高场区(即电极注入的SCLC区)不完全是由一种与注入载流子相同的载流子决定的想法,特别是要严格审视在测量条件确定时,离子电导对低场与高场区电流的贡献。为此,列出了离子电导与电子电导的主要特征与区别方法。针对脉冲有关的测量空间电荷的方法,特别是已成为国际上测量空间电荷主流方法的脉冲电声(PEA)方法,提出了PEA的优点与不足之处,以及如何去校准测量结果的正确性、重复性,如依据高聚物结构的特征,建立压激电流(pressure stimulated current,PSC)装置,正确判断电子、离子、偶极子梯度产生的空间电荷,以弥补PEA测量的严重不足。展开更多
从电导特性的角度研究了变压器油在高场强下的预击穿过程及机制,将变压器油在不同电场下的电导机制分为3个阶段:①在电场低于0.44 kV mm 1时,电导电流I与外施场强E成正的线性关系,符合欧姆定律;②电场强度在0.44 1.33 kV mm 1范围内时,l...从电导特性的角度研究了变压器油在高场强下的预击穿过程及机制,将变压器油在不同电场下的电导机制分为3个阶段:①在电场低于0.44 kV mm 1时,电导电流I与外施场强E成正的线性关系,符合欧姆定律;②电场强度在0.44 1.33 kV mm 1范围内时,ln(I/E2)1/E成正比,满足Fowler-Nordheim场致发射方程,属于隧道效应电流阶段;③当油中电场强度E>1.33 kV mm 1,I与电压的二次方U2成正比,属于空间电荷限制电流阶段,载流子视在迁移率c约为2.93 10 3cm2/(V s),当外施电场为2 kV mm 1时,载流子流速v为0.586 m s 1,电流体力学迁移率h约为1.5 10 3cm2(V s)1。同时,对影响变压器油电导特性的温度、流体压强、油中含水等因素进行研究,试验结果表明,随着温度的升高、流体压强的减小以及油中含水量的增加,变压器油的电导电流均将明显增加。此外,对工程上关注的不同浸油程度的绝缘纸板的电导和介电特性及其影响因素进行研究,结果表明,随着浸油水平、温度和工作频率的提高,绝缘纸板的电导电流均将相应增加。展开更多
阻变式存储器(resistive random access memory,RRAM)是以材料的电阻在外加电场作用下可在高阻态和低阻态之间实现可逆转换为基础的一类前瞻性下一代非挥发存储器.它具有在32nm节点及以下取代现有主流Flash存储器的潜力,成为目前新型存...阻变式存储器(resistive random access memory,RRAM)是以材料的电阻在外加电场作用下可在高阻态和低阻态之间实现可逆转换为基础的一类前瞻性下一代非挥发存储器.它具有在32nm节点及以下取代现有主流Flash存储器的潜力,成为目前新型存储器的一个重要研究方向.但阻变式存储器的电阴转变机理不明确,制约它的进一步研发与应用.文章对阻变式存储器的体材料中几种基本电荷输运机制进行了归纳,总结了目前对阻变式存储器存储机理的理论模型.展开更多
文摘The current-voltage（I-V） characteristics of cBN crystal sandwiched between two metallic electrodes are measured and found to be nonlinear. Over 20 samples are measured at room temperature with various electrodes, and the resulting curves are all similar in shape. When a voltage of about 560V is applied to the cBN crystal, the emitted light is visible to the naked eye in a dark room. We explain these phenomena by the space charge limited current and the electronic transition between the X and Г valleys of the conduction band.
文摘Organic solar cells with inverted planar heterojunction structure based on subphthalocya- nine and C60 were fabricated using several kinds of materials as cathode buffer layer （CBL）, including tris-8-hydroxy-quinolinato aluminum （Alq3）, bathophenanthroline （Bphen）, bathocuproine, 2,3,8,9,14,15-hexakis-dodecyl-sulfanyl-5,6,11,12,17,18-hexaazatrinaphthylene （HATNA）, and an inorganic compound of Cs2CO3. The influence of the lowest unoccupied molecular orbital level and the electron mobility of organic CBL on the solar cells perfor- mance was compared. The results showed that Alq3, Bphen, and HATNA could significantly improve the device performance. The highest efficiency was obtained from device with an- nealed HATNA as CBL and increased for more than 7 times compared with device without CBL. Furthermore~ the simulation results with space charge-limited current theory indicated that the Schottky barrier at the organic/electrode interface in inverted OSC structure was reduced for 27% by inserting HATNA CBL.
基金This study was supported by the projects of National Research Foundation of Korea(Project No.:NRF-2018R1D1A1B07048843,Ministry of Education and NRF-2018K2A9A2A06023902,Ministry of Science and ICT)in addition to the program for Changbaishan Scholars of Jilin Province,China.
文摘To understand the complex behaviors of photogenerated charge carriers within polymer-based bulk-heterojunction-type solar cells,the charge-carrier photogeneration and extraction dynamics are simultaneously estimated using a transient photocurrent technique under various external-bias voltages,and a wide range of excitation intensities are analyzed.For this purpose,conventional devices with 80 nm thick active layers consisting of a blend of representative P3HT and PTB7 electron-donating polymers and proper electron-accepting fullerene derivatives were used.After the correction for the saturation behavior at a high excitation-intensity range nearby the regime of the space charge-limited current,the incident-photon-density-dependent maximum photocurrent densities at the initial peaks are discussed as the proportional measures of the charge-carrier-photogeneration facility.By comparing the total number of the extracted charge carriers to the total number of the incident photons and the number of the initially photogenerated charge carriers,the external quantum efficiencies as well as the extraction quantum efficiencies of the charge-carrier collection during a laser-pulse-induced transient photocurrent process were obtained.Subsequently,the charge-carrier concentration-dependent mobility values were obtained,and they are discussed in consideration of the additional influences of the charge-carrier losses from the device during the charge-carrier extraction that also affects the photocurrent-trace shape.
文摘随着工程电介质领域研究的发展,诸多没有得到公认解释的问题逐渐出现,为此,本文提出了几个重要的问题及思考以供相关研究工作者参考。1994年Lewis首次提出了纳米电介质,2003年至今已成为工程电介质领域的研究热点,但从20余年该领域的研究内容、作者的原意以及新近又提出的纳米结构电介质来看,我们认为应把名称改为纳米电介质复合物,并按照低维物理对纳米电介质作了重新定义。分析了Lewis与Tanaka界面的具体含义,提出了纳米高聚物复合物硬/软界面及其具有结构复杂性、不确定性与易变性的新概念,并剖析了硬、软表面的尺度及理化特性。提出了从A Einstein还原论、P W Anderson的层展现象与R P Feynmann的思维方法以启迪相关研究的新思维。从空间电荷限制电流(SCLC)存在条件的约束和高聚物或其复合物中由于自身结构的多层次性、复杂界面、电极接触以及共存的电子与离子电导等因素的严重影响,提出了从欧姆区过渡到高场区(即电极注入的SCLC区)不完全是由一种与注入载流子相同的载流子决定的想法,特别是要严格审视在测量条件确定时,离子电导对低场与高场区电流的贡献。为此,列出了离子电导与电子电导的主要特征与区别方法。针对脉冲有关的测量空间电荷的方法,特别是已成为国际上测量空间电荷主流方法的脉冲电声(PEA)方法,提出了PEA的优点与不足之处,以及如何去校准测量结果的正确性、重复性,如依据高聚物结构的特征,建立压激电流(pressure stimulated current,PSC)装置,正确判断电子、离子、偶极子梯度产生的空间电荷,以弥补PEA测量的严重不足。
文摘从电导特性的角度研究了变压器油在高场强下的预击穿过程及机制,将变压器油在不同电场下的电导机制分为3个阶段:①在电场低于0.44 kV mm 1时,电导电流I与外施场强E成正的线性关系,符合欧姆定律;②电场强度在0.44 1.33 kV mm 1范围内时,ln(I/E2)1/E成正比,满足Fowler-Nordheim场致发射方程,属于隧道效应电流阶段;③当油中电场强度E>1.33 kV mm 1,I与电压的二次方U2成正比,属于空间电荷限制电流阶段,载流子视在迁移率c约为2.93 10 3cm2/(V s),当外施电场为2 kV mm 1时,载流子流速v为0.586 m s 1,电流体力学迁移率h约为1.5 10 3cm2(V s)1。同时,对影响变压器油电导特性的温度、流体压强、油中含水等因素进行研究,试验结果表明,随着温度的升高、流体压强的减小以及油中含水量的增加,变压器油的电导电流均将明显增加。此外,对工程上关注的不同浸油程度的绝缘纸板的电导和介电特性及其影响因素进行研究,结果表明,随着浸油水平、温度和工作频率的提高,绝缘纸板的电导电流均将相应增加。
文摘阻变式存储器(resistive random access memory,RRAM)是以材料的电阻在外加电场作用下可在高阻态和低阻态之间实现可逆转换为基础的一类前瞻性下一代非挥发存储器.它具有在32nm节点及以下取代现有主流Flash存储器的潜力,成为目前新型存储器的一个重要研究方向.但阻变式存储器的电阴转变机理不明确,制约它的进一步研发与应用.文章对阻变式存储器的体材料中几种基本电荷输运机制进行了归纳,总结了目前对阻变式存储器存储机理的理论模型.
