量子点是一种半导体纳米晶体,因其发光波长可调、颜色纯度高、色域广、寿命长、可溶液法制备受到广泛关注。量子点发光二极管(QLED)以其优越的发光性能、高效的能量转换效率,成为下一代平板显示、照明和可穿戴设备等领域的候选方案。顶...量子点是一种半导体纳米晶体,因其发光波长可调、颜色纯度高、色域广、寿命长、可溶液法制备受到广泛关注。量子点发光二极管(QLED)以其优越的发光性能、高效的能量转换效率,成为下一代平板显示、照明和可穿戴设备等领域的候选方案。顶发射是一种发光二极管结构,最后蒸镀的电极方向即为出光方向,不同于底发射,它的出光不需要经过驱动薄膜晶体管(TFT),因此其开口率高,是OLED/QLED显示的一种选择方案。顶发射QLED从顶电极一侧出光,因此,提高顶电极的出光效率是一个重要课题。通常在顶部电极上覆盖一层光提取层(Extraction Layer, EXL),调整功能层和光提取层之间的折射率差异,以提高出光率,同时采用光散射层(Scattering Layer, SCL)抑制微腔效应造成的出光角度不均匀问题。但是,通过调整功能层厚度来匹配光提取层折射率的方法会使得器件的电荷平衡性遭到破坏,同时现有的光散射层的制备过程涉及光刻、刻蚀等工艺,比较复杂,也易破坏器件功能层。基于此,本论文研究了光提取材料的筛选原则,使用了与量子点发光层折射率相匹配的光提取材料,优化光提取层厚度,提升了器件电流效率。另外,通过旋涂工艺,引入了光学纳米材料对出光施加散射,对比发现,粗糙度更大的纳米颗粒能够显著抑制光的角度分布不均匀问题。实验结果显示,优化后的顶电极结构使得器件的电流效率从14.8 cd/A提升到17.9 cd/A,而且器件的出光角度更加分散。Quantum dots are semiconductor nanocrystals that have garnered significant attention due to their tunable emission wavelengths, high color purity, wide color gamut, long lifetimes, and solution-processable fabrication. Quantum dot light-emitting diodes (QLEDs), renowned for their superior luminescent properties and high energy conversion efficiency, are emerging as potential candidates for next-generation flat-panel displays, lighting, and wearable devices. Top-emission is a type of light-emitting diode structure where the direction of the light emission corresponds to the direction of the final deposited electrode. Unlike bottom-emission, top-emission does not require the light to pass through the driving thin-film transistors (TFTs), resulting in a higher aperture ratio, making it a viable option for OLED/QLED displays. In top-emission QLEDs, light is emitted from the top electrode, making the improvement of the top electrode’s light extraction efficiency a critical issue. Typically, a light extraction layer (EXL) is applied over the top electrode to enhance light extraction by adjusting the refractive index difference between the functional layer and the light extraction layer. Additionally, a scattering layer (SCL) is used to mitigate the uneven light emission angle caused by the microcavity effect. However, adjusting the functional layer thickness to match the refractive index of the light extraction layer can disrupt the device’s charge balance. Furthermore, the current preparation process for scattering layers involves complex techniques like photolithography and etching, which can damage the functional layers of the device. In this context, the present study investigates the selection criteria for light extraction materials. By employing light extraction materials that match the refractive index of the quantum dot emission layer and optimizing the thickness of the light extraction layer, the device’s current efficiency is enhanced. Additionally, the introduction of optical nanomaterials via spin-coating applies scattering to the emitted light. Comparative analysis reveals that nanomaterials with greater roughness significantly suppress the uneven angular distribution of light. Experimental results demonstrate that the optimized top electrode structure increases the device’s current efficiency from 14.8 cd/A to 17.9 cd/A, while also achieving a more diffuse light emission angle.展开更多
Melt treatment is well known to have an important influence on the properties of metallic glasses(MGs).However,for the MGs quenched from different melt temperatures with a quartz tube,the underlying physical origin re...Melt treatment is well known to have an important influence on the properties of metallic glasses(MGs).However,for the MGs quenched from different melt temperatures with a quartz tube,the underlying physical origin responsible for the variation of properties remains poorly understood.In the present work,we systematically studied the influence of melt treatment on the thermal properties of a Zr50Cu36Al14 glass-forming alloy and unveiled the microscopic origins.Specifically,we quenched the melt at different temperatures ranging from 1.1Tl to 1.5Tl(Tl is the liquidus temperature)to obtain melt-spun MG ribbons and investigated the variation of thermal properties of the MGs upon heating.We found that glass transition temperature,Tg,increases by as much as 36 K,and the supercooled liquid region disappears in the curve of differential scanning calorimetry when the melt is quenched at a high temperature up to 1.5Tl.The careful chemical analyses indicate that the change in glass transition behavior originates from the incorporation of oxygen and silicon in the molten alloys.The incorporated oxygen and silicon can both enhance the interactions between atoms,which renders the cooperative rearrangements of atoms difficult,and thus enhances the kinetic stability of the MGs.展开更多
热塑性聚丙烯系列聚合物具有绝缘性能优异、耐温性能好、无交联副产物以及可回收再利用等优点,是新兴绿色环保电力电缆绝缘材料。在高压电缆中,绝缘必须与半导电屏蔽配合良好,因此亟待开发基于热塑性聚丙烯的半导电屏蔽料。该文以聚丙...热塑性聚丙烯系列聚合物具有绝缘性能优异、耐温性能好、无交联副产物以及可回收再利用等优点,是新兴绿色环保电力电缆绝缘材料。在高压电缆中,绝缘必须与半导电屏蔽配合良好,因此亟待开发基于热塑性聚丙烯的半导电屏蔽料。该文以聚丙烯和聚烯烃弹性体共混物为基体,碳黑和MXene为导电填料,马来酸酐接枝聚丙烯(PP-g-MAH)为改性剂,制备了导电填料添加质量分数为30.0%的半导电屏蔽料。研究表明,引入MXene能显著降低半导电屏蔽料的电阻率,MXene质量分数为1.0%时(碳黑为29.0%),屏蔽料的正温度系数(positive temperature coefficient,PTC)强度为0.84,显著低于添加30.0%碳黑屏蔽料的PTC强度(1.49)。在添加29.0%碳黑和1.0%MXene的屏蔽料中引入1.0%PP-g-MAH可显著提高热稳定性,但电阻率和PTC强度(1.04)略高于MXene含量为1.0%时(碳黑为29.0%)的屏蔽料。另外,在碳黑屏蔽料电极中加入MXene可显著减少PP绝缘料中的空间电荷数量。该研究为开发热塑性高压电缆屏蔽料提供了实验参考。展开更多
文摘量子点是一种半导体纳米晶体,因其发光波长可调、颜色纯度高、色域广、寿命长、可溶液法制备受到广泛关注。量子点发光二极管(QLED)以其优越的发光性能、高效的能量转换效率,成为下一代平板显示、照明和可穿戴设备等领域的候选方案。顶发射是一种发光二极管结构,最后蒸镀的电极方向即为出光方向,不同于底发射,它的出光不需要经过驱动薄膜晶体管(TFT),因此其开口率高,是OLED/QLED显示的一种选择方案。顶发射QLED从顶电极一侧出光,因此,提高顶电极的出光效率是一个重要课题。通常在顶部电极上覆盖一层光提取层(Extraction Layer, EXL),调整功能层和光提取层之间的折射率差异,以提高出光率,同时采用光散射层(Scattering Layer, SCL)抑制微腔效应造成的出光角度不均匀问题。但是,通过调整功能层厚度来匹配光提取层折射率的方法会使得器件的电荷平衡性遭到破坏,同时现有的光散射层的制备过程涉及光刻、刻蚀等工艺,比较复杂,也易破坏器件功能层。基于此,本论文研究了光提取材料的筛选原则,使用了与量子点发光层折射率相匹配的光提取材料,优化光提取层厚度,提升了器件电流效率。另外,通过旋涂工艺,引入了光学纳米材料对出光施加散射,对比发现,粗糙度更大的纳米颗粒能够显著抑制光的角度分布不均匀问题。实验结果显示,优化后的顶电极结构使得器件的电流效率从14.8 cd/A提升到17.9 cd/A,而且器件的出光角度更加分散。Quantum dots are semiconductor nanocrystals that have garnered significant attention due to their tunable emission wavelengths, high color purity, wide color gamut, long lifetimes, and solution-processable fabrication. Quantum dot light-emitting diodes (QLEDs), renowned for their superior luminescent properties and high energy conversion efficiency, are emerging as potential candidates for next-generation flat-panel displays, lighting, and wearable devices. Top-emission is a type of light-emitting diode structure where the direction of the light emission corresponds to the direction of the final deposited electrode. Unlike bottom-emission, top-emission does not require the light to pass through the driving thin-film transistors (TFTs), resulting in a higher aperture ratio, making it a viable option for OLED/QLED displays. In top-emission QLEDs, light is emitted from the top electrode, making the improvement of the top electrode’s light extraction efficiency a critical issue. Typically, a light extraction layer (EXL) is applied over the top electrode to enhance light extraction by adjusting the refractive index difference between the functional layer and the light extraction layer. Additionally, a scattering layer (SCL) is used to mitigate the uneven light emission angle caused by the microcavity effect. However, adjusting the functional layer thickness to match the refractive index of the light extraction layer can disrupt the device’s charge balance. Furthermore, the current preparation process for scattering layers involves complex techniques like photolithography and etching, which can damage the functional layers of the device. In this context, the present study investigates the selection criteria for light extraction materials. By employing light extraction materials that match the refractive index of the quantum dot emission layer and optimizing the thickness of the light extraction layer, the device’s current efficiency is enhanced. Additionally, the introduction of optical nanomaterials via spin-coating applies scattering to the emitted light. Comparative analysis reveals that nanomaterials with greater roughness significantly suppress the uneven angular distribution of light. Experimental results demonstrate that the optimized top electrode structure increases the device’s current efficiency from 14.8 cd/A to 17.9 cd/A, while also achieving a more diffuse light emission angle.
基金The work was financially supported by the National Key Research and Development Program of China(Grant Nos.2018YFA0703600,2021YFA0716302,and 2021YFA0718703)the National Natural Science Foundation of China(Grant Nos.51825104 and 52192602)China Postdoctoral Science Foundation(Grant No.2022T150691).
文摘Melt treatment is well known to have an important influence on the properties of metallic glasses(MGs).However,for the MGs quenched from different melt temperatures with a quartz tube,the underlying physical origin responsible for the variation of properties remains poorly understood.In the present work,we systematically studied the influence of melt treatment on the thermal properties of a Zr50Cu36Al14 glass-forming alloy and unveiled the microscopic origins.Specifically,we quenched the melt at different temperatures ranging from 1.1Tl to 1.5Tl(Tl is the liquidus temperature)to obtain melt-spun MG ribbons and investigated the variation of thermal properties of the MGs upon heating.We found that glass transition temperature,Tg,increases by as much as 36 K,and the supercooled liquid region disappears in the curve of differential scanning calorimetry when the melt is quenched at a high temperature up to 1.5Tl.The careful chemical analyses indicate that the change in glass transition behavior originates from the incorporation of oxygen and silicon in the molten alloys.The incorporated oxygen and silicon can both enhance the interactions between atoms,which renders the cooperative rearrangements of atoms difficult,and thus enhances the kinetic stability of the MGs.
文摘热塑性聚丙烯系列聚合物具有绝缘性能优异、耐温性能好、无交联副产物以及可回收再利用等优点,是新兴绿色环保电力电缆绝缘材料。在高压电缆中,绝缘必须与半导电屏蔽配合良好,因此亟待开发基于热塑性聚丙烯的半导电屏蔽料。该文以聚丙烯和聚烯烃弹性体共混物为基体,碳黑和MXene为导电填料,马来酸酐接枝聚丙烯(PP-g-MAH)为改性剂,制备了导电填料添加质量分数为30.0%的半导电屏蔽料。研究表明,引入MXene能显著降低半导电屏蔽料的电阻率,MXene质量分数为1.0%时(碳黑为29.0%),屏蔽料的正温度系数(positive temperature coefficient,PTC)强度为0.84,显著低于添加30.0%碳黑屏蔽料的PTC强度(1.49)。在添加29.0%碳黑和1.0%MXene的屏蔽料中引入1.0%PP-g-MAH可显著提高热稳定性,但电阻率和PTC强度(1.04)略高于MXene含量为1.0%时(碳黑为29.0%)的屏蔽料。另外,在碳黑屏蔽料电极中加入MXene可显著减少PP绝缘料中的空间电荷数量。该研究为开发热塑性高压电缆屏蔽料提供了实验参考。
