A Polymer Defect Passivator for Efficient Hole-Conductor-Free Printable Mesoscopic Perovskite Solar Cells

Due to the low cost and excellent potential for mass production, printable mesoscopic perovskite solar cells (p-MPSCs) have drawn a lot of attention among other device structures. However, the low open-circuit voltage (V_OC) of such devices restricts their power conversion efficiency (PCE). This limitation is brought by the high defect density at perovskite grain boundaries in the mesoporous scaffold, which results in severe nonradiative recombination and is detrimental to the V_OC. To improve the perovskite crystallization process, passivate the perovskite defects, and enhance the PCE, additive engineering is an effective way. Herein, a polymeric Lewis base polysuccinimide (PSI) is added to the perovskite precursor solution as an additive. It improves the perovskite crystallinity and its carbonyl groups strongly coordinate with Pb²⁺, which can effectively passivate defects. Additionally, compared with its monomer, succinimide (SI), PSI serves as a better defect passivator because the long-chained macromolecule can be firmly anchored on those defect sites and form a stronger interaction with perovskite grains. As a result, the champion device has a PCE of 18.84%, and the V_OC rises from 973 to 1030 mV. This study offers a new strategy for fabricating efficient p-MPSCs.     

Kinetically Accelerating Elementary Steps via Bridged Ru-H State for the Hydrogen-Evolution in Anion-Exchange Membrane Electrolyzer

Designing hydrogen evolution reaction (HER) electrocatalysts for facilitating its sluggish adsorption kinetics is crucial in generating green hydrogen via sustainable water electrolysis. Herein, a high-performance ultra-low Ruthenium (Ru) catalyst is developed consisting of atomically-layered Ru nanoclusters with adjacent single Ru sites, which executs a bridging-Ru-H activation strategy to kinetically accelerate the HER elementary steps. Owing to its optimal electronic structure and unique adsorption configuration, the hybrid Ru catalyst simultaneously displayed a drastically reduced overpotential of 16 mV at 10 mA cm⁻² as well as a low Tafel slope of 35.2 mV dec⁻¹ in alkaline electrolyte. When further coupled with a commercial IrO₂ anode catalyst, the ensembled anion-exchange membrane water electrolyzer achievs a current density of 1.0 A cm⁻² at a voltage of only 1.70 V_cell. In situ spectroscopic analysis verified that Ru single atom and atomically-layered Ru nanoclusters in the hybrid materials play a critical role in facilitating water dissociation and weakening *H adsorption, respectively. Theoretical calculations further elucidate the underlaying mechanism, suggesting that the dissociated proton at the single atom Ru site orients itself adjacently with Ru nanoclusters in a bridged structure through targeted charge transfer, thus promoting Volmer-Heyrovsky dynamics and boosting the HER activity.     

Indirect Exciton–Phonon Dynamics in MoS2 Revealed by Ultrafast Electron Diffraction

Transition metal dichalcogenides layered nano-crystals are emerging as promising candidates for next-generation optoelectronic and quantum devices. In such systems, the interaction between excitonic states and atomic vibrations is crucial for many fundamental properties, such as carrier mobilities, quantum coherence loss, and heat dissipation. In particular, to fully exploit their valley-selective excitations, one has to understand the many-body exciton physics of zone-edge states. So far, theoretical and experimental studies have mainly focused on the exciton–phonon dynamics in high-energy direct excitons involving zone-center phonons. Here, ultrafast electron diffraction and ab initio calculations are used to investigate the many-body structural dynamics following nearly- resonant excitation of low-energy indirect excitons in MoS₂. By exploiting the large momentum carried by scattered electrons, the excitation of in-plane K- and Q- phonon modes are identified with 𝑬^′ symmetry as key for the stabilization of indirect excitons generated via near-infrared light at 1.55 eV, and light is shed on the role of phonon anharmonicity and the ensuing structural evolution of the MoS₂ crystal lattice. The results highlight the strong selectivity of phononic excitations directly associated with the specific indirect- exciton nature of the wavelength-dependent electronic transitions triggered in the system.     

IGBT芯片静态输出曲线连续测量方法

绝缘栅双极型晶体管(IGBT)芯片的静态输出曲线是考核其能量损耗及指导多芯片并联设计的重要指标之一。现有测量IGBT静态输出曲线的方法多采用商用化的功率器件分析仪,然而商业化功率器件分析仪存在价格昂贵、夹具单一的问题。亟需开发一种简单、快速、有效的静态输出曲线测量方法。面向高压IGBT芯片,提出一种新的静态输出曲线连续测量方法及测试电路,有效减小了IGBT芯片的电导调制效应和温升效应对静态输出曲线的影响。通过实时测量动态过程中的电压及电流,可以快速得到IGBT芯片静态输出曲线。通过对比本文连续法与功率器件分析仪的测量结果,证明了所提方法的有效性。     

Nb∶SrTiO3阻变单元及1T1R复合结构的电离辐射总剂量效应研究

开展了Nb∶SrTiO_(3)阻变单元及1T1R复合结构的X射线总剂量效应实验研究。结果表明,Nb∶SrTiO_(3)阻变单元在累积剂量达到10 Mrad(Si)时依然能够保持良好的阻变特性,高、低阻态未发生逻辑混乱。1T1R复合结构中的NMOS选通晶体管对电离辐射较为敏感,在栅氧化层中辐射感生氧化物陷阱电荷的作用下,NMOS器件阈值电压逐渐向负方向漂移,泄漏电流逐渐增加,进一步导致关态条件下(V_(G)=0 V)对阻变存储单元的错误读写。通过选用抗辐射加固NMOS选通晶体管,可显著提升1T1R复合结构的抗总剂量能力。     

溅射法制备n型碲化镉薄膜的光电化学特性研究

采用溅射法制备了n型碲化镉薄膜。研究了不同沉积时间制备的n型碲化镉薄膜的形貌、结构和光学性质,以及薄膜厚度和退火工艺对n型碲化镉薄膜光电化学特性的影响。实验结果表明,溅射时间为25 min的碲化镉薄膜具有较好的PEC性能。退火工艺可以提高沉积的n型碲化镉薄膜的光电化学性能。当用饱和氯化镉溶液涂覆碲化镉薄膜并在真空中400 ℃退火时,n型碲化镉薄膜的光电化学性能最佳,光电流达到301 μA/cm²。     

雷达辐射源信号分选研究进展

雷达辐射源信号分选是雷达信号侦察的关键技术之一,同时也是战场态势感知的重要环节。该文系统梳理了雷达辐射源信号分选的主流技术,从基于脉间调制特征、基于脉内调制特征、基于机器学习的雷达辐射源信号分选3个角度阐述了目前雷达辐射源信号分选工作的主要研究方向及进展,并重点阐释了基于深度神经网络、数据流聚类等最新分选技术的原理与特点。最后,对现有雷达辐射源信号分选技术的不足进行了总结并对未来趋势进行了预测。      

提升小波与能量检测联合优化下的频谱感知方法北大核心CSCD

传统的频谱感知方法易受噪声波动的干扰,而且在低信噪比的无线通信条件下检测精度较差。通过结合提升小波去噪与动态门限能量检测算法,能有效提高传统频谱感知方法的抗噪声性能和检测精度。首先对含噪信号进行奇偶抽样,分解信号,去除噪声部分,再重构为去噪新信号,然后通过能量检测方法来统计信号的能量积累,设置动态门限,最后以动态门限判断用户信号是否存在。提升小波去噪能够有效地去除采样信号中的噪声,减少噪声对能量检测法检测精度的影响,动态门限能根据噪声波动进行调整来适应复杂的噪声环境。仿真结果表明,提升小波去噪结合动态门限能量检测算法相比于传统的频谱感知要有更优的检测精度。此方法不但提高了其对不确定噪声的抵抗性,使之能适应复杂的通信环境,而且提高了频谱感知过程的可靠性。