Paving the Way for High-Performance UVB-LEDs Through Substrate-Dominated Strain-Modulation

AlGaN-based ultraviolet-B light-emitting diodes (UVB-LEDs) exhibit great potential in phototherapy, vitamin D3 synthesis promotion, plant growth regulation, and so on. However, subjected to the excess compressive strain induced by the large lattice mismatch between multiple quantum wells (MQWs) and AlN, UVB-LEDs that simultaneously satisfy the requirements of high light output power (LOP), low working voltage, and excellent stability are rarely reported. Here, a substrate-dominated strain-modulation strategy is proposed. By precisely manipulating the strain in AlN grown on nano-patterned sapphire substrate (NPSS) to a slightly tensile one, the compressive strain in the following Al_0.55Ga_0.45N underlayer and Al_0.28Ga_0.72N/Al_0.45Ga_0.55N MQWs is successfully suppressed. As a result, an outstanding UVB-LED with a peak wavelength at 303.6 nm is achieved. The 20 × 20 mil² UVB-LED chip shows a wall-plug efficiency (WPE) of 3.27% under a forward current of 20 mA and a high LOP of 57.2 mW with an extremely low voltage of 5.87 V under a forward current of 800 mA. It is more exciting that the LOP degradation is as low as 17% after 1000 h operation under a forward current density of 75 A cm⁻², showing excellent stability. The here-developed UVB-LED, with a high LOP and excellent reliability, will definitely promote the applications of AlGaN-based UVB-LEDs.     

A Self-Assembled Vertical-Gradient and Well-Dispersed MXene Structure for Flexible Large-Area Perovskite Modules

Advancing hole transport layers (HTL) to realize large-area, flexible, and high-performance perovskite solar cells (PSCs) is one of the most challenging issues for its commercialization. Here, a self-assembled gradient Ti₃C₂T_x MXene incorporated PEDOT:PSS HTL is demonstrated to achieve high-performance large-area PSCs by establishing half-caramelization-based glucose-induced MXene redistribution. Through this process, the Ti₃C₂T_x MXene nanosheets are spontaneously dispersed and redistributed at the top region of HTL to form the unique gradient distribution structure composed of MXene:Glucose:PEDOT:PSS (MG-PEDOT). These results show that the MG-PEDOT HTL not only offers favorable energy level alignment and efficient charge extraction, but also improves the film quality of perovskite layer featuring enlarged grain size, lower trap density, and longer carrier lifetime. Consequently, the power conversion efficiency (PCE) of the flexible device based on MG-PEDOT HTL is increased by 36% compared to that of pristine PEDOT:PSS HTL. Meanwhile, the flexible perovskite solar minimodule (15 cm² area) using MG-PEDOT HTL achieve a PCE of 17.06%. The encapsulated modules show remarkable long-term storage stability at 85 °C in ambient air (≈90% efficiency retention after 1200 h) and enhanced operational lifetime (≈90% efficiency retention after 200 h). This new approach shows a promising future of the self-assembled HTLs for developing optoelectronic devices.     

软开关技术的分析研究

在对市场及研究领域中最受青睐的软开关技术进行分析的基础上,根据软开关表现出来的优良特性以及结构特点,对变换器进行了整合研究。     

频率覆盖3.2～6.1 GHz的CMOS LC VCO

通过提高MIM电容的调整范围,实现了一个覆盖3.2～6.1 GHz的CMOS LC VCO.该VCO使用0.18μm射频CMOS工艺制作,芯片面积约为1260μm×670μm.当输出5.5GHz时,VCO内核消耗功率为17.5mW;在100kHz频偏处的相位噪声是～101.67dBc/Hz.     

凹槽栅场板结构的AlGaN/GaN HEMT特性分析

研究了无场调制板结构、有场调制板结构但无凹槽栅、结合场调制板结构和凹槽栅工艺三种AlGaN/GaN HEMT的动态I-V特性和微波特性,认为场调制板结构和凹槽栅工艺可以有效改善AlGaN/GaN HEMT器件沟道内电场分布,显著减小电流崩塌现象,提高器件的微波输出功率特性.利用此技术研制的1mm栅宽AlGaN/GaNHEMT输出功率大于10W.     

ISAR成像中一种距离对准的新方法

本文采用一维距离像相关模型,提出一种ISAR成像中距离对准的新方法,该方法充分考虑了一维距离像间的直流漂移和归一化系数,且具有较好的对准效果,通过实测数据验证了该方法的有效性。     

基于CPLD设计实现单横单纵激光器种子注入纵模锁定

基于自滤波非稳腔、种子激光注入及CPLD控制的干涉法纵模锁定技术,研制出一套单横单纵激光器系统；对激光器的工作原理及纵模锁定电路设计进行了说明。该设计具有输出光束质量好,工作稳定,抗干扰性强的特点。该激光器经历了在强干扰环境中长时间的“烤机”实验,单纵模锁定概率达100%。     

电子设备电源系统的谐波特性研究

电子设备的电源系统或电力系统中,存在多种类型的谐波源,分为谐波电流源和谐波电压源,本文针对典型电源系统开关电源系统进行分类和建模,给出各类谐波源的特征,并对容性滤波整流电路的谐波特性进行了分析.     

传导EMI的测试

在传导EMI(电磁干扰)中既存在共模电流也存在差模电流,要很好的分析传导EMI系统,就很有必要对共模干扰信号和差模干扰信号分离开来单独进行测试.这样,共模和差模噪声的分离就显得很重要了.     

高端虚拟演播室系统设计

虚拟演播室系统是传统演播室的色键技术与计算机图形图像处理技术相结合的产物。它将计算机制作的虚拟场景与电视摄像机现场拍摄的人物进行数字化合成从而获得完美的合成电视画面。本文在分析虚拟演播室系统工作原理的基础上,着重介绍了系统构成及设计问题,并给出了设计举例。