Probing into Reverse Bias Dark Current in Perovskite Photodiodes: Critical Role of Surface Defects

Minimizing reverse bias dark current density (J_dark) while retaining high external quantum efficiency is crucial for promising applications of perovskite photodiodes, and it remains challenging to elucidate the ultimate origin of J_dark. It is demonstrated in this study that the surface defects induced by iodine vacancies are the main cause of J_dark in perovskite photodiodes. In a targeted way, the surface defects are thoroughly passivated through a simple treatment with butylamine hydroiodide to form ultrathin 2D perovskite on its 3D bulk. In the passivated perovskite photodiodes, J_dark as low as 3.78 × 10^-10 A cm^-2 at -0.1 V is achieved, and the photoresponse is also enhanced, especially at low light intensities. A combination of the two improvements realizes high specific detectivity up to 1.46 × 10¹² Jones in the devices. It is clarified that the trap states induced by the surface defects can not only raise the generation-recombination current density associated with the Shockley–Read–Hall mechanisms in the dark (increasing J_dark), but also provide additional carrier recombination paths under light illumination (decreasing photocurrent). The critical role of surface defects on J_dark of perovskite photodiodes suggests that making trap-free perovskite thin films, for example, by fine preparation and/or surface engineering, is a top priority for high-performance perovskite photodiodes.     

Electrical and Thermal Transport Properties of Ge1–xPbxCuySbyTeSe2y

Balancing the contradictory relationship between thermoelectric parameters, such as effective mass and carrier mobility, is a challenge to optimize thermoelectric performance. Herein, the exceptional thermoelectric performance is realized in GeTe through collaboratively optimizing the carrier and phonon transport via stepwise alloying Pb and CuSbSe₂. The formation energy of Ge vacancy is efficiently bolstered by alloying Pb, which reduces carrier density and carrier scattering to maintain superior carrier mobility in GeTe. Additionally, CuSbSe₂, acting as an n-type dopant, further modulates carrier density and validly equilibrates carrier mobility and effective mass. Accordingly, the promising power factor of 45 µW cm⁻¹ K⁻² is achieved at 723 K. Meanwhile, point defects are found to significantly suppress phonons transport to descend lattice thermal conductivity by Pb and CuSbSe₂ alloying, which barely impacts the carrier mobility. A combination with superior carrier mobility and lower lattice thermal conductivity, a maximum ZT of 2.2 is attained in Ge_0.925Pb_0.075Cu_0.005Sb_0.005TeSe_0.01, which corresponds to a 100% promotion compared with that of intrinsic GeTe. This study provides a new indicator for optimizing carrier and phonon transport properties by balancing interrelated thermoelectric parameters.     

Self-Mineralizing Dnazyme Hydrogel as a Multifaceted Bone Microenvironment Amendment for Promoting Osteogenesis in Osteoporosis

The accumulation of reactive oxygen species (ROS) and minimal osteogenic raw material in the osteoporotic bone microenvironment greatly inhibits the activity of osteoblasts. Herein, it is originally proposed to construct a biomatrix multifaceted bone microenvironment amendment -Mineralized zippered G4-Hemin DNAzyme hydrogel (MDH)-to improve osteoporotic osteogenic capacity and promote high-quality bone defect repair. The programmed design of the rolling circle amplified DNA hydrogel synthesis system allows the introduction of massive amounts of zippered G4-Hemin DNAzyme in MDH. The zippered G4-Hemin DNAzyme highly mimics the tight catalytic configuration of horseradish peroxidase and exerts excellent enzyme-like activity with considerable ROS molecule scavenging ability. In addition, the DNA amplification by-product pyrophosphate is ingeniously employed as a sufficient phosphorus source, thus constituting an autonomous mineralization system for waste reuse through the introduction of pyrophosphate hydrolase and calcium ions, which deposits in MDH as an osteogenic raw material and addresses the challenge of DNA hydrogel bio-application stability. The remarkable in vitro and in vivo outcomes demonstrate that MDH can effectively improve the oxidative stress status of osteoblasts, restore the balance of mitochondrial membrane potential, and reduce apoptosis, ultimately demonstrating superior osteogenic capacity.     

Spidermen Strategy for Stable 24% Efficiency Perovskite Solar Cells

The interface energetics-modification plays an important role in improving the power conversion efficiency (PCE) among the perovskite solar cells (PSCs). Considering the low carrier mobility caused by defects in PSCs, a double-layer modification engineering strategy is adopted to introduce the “spiderman” NOBF₄ (nitrosonium tetrafluoroborate) between tin dioxide (SnO₂ and perovskite layers. NO⁺, as the interfacial bonding layer, can passivate the oxygen vacancy in SnO₂, while BF₄⁻ can optimize the defects in the bulk of perovskite. This conclusion is confirmed by theoretical calculation and transmission electron microscopy (TEM). The synergistic effect of NO⁺ and BF₄⁻ distinctly heightens the carrier extraction efficiency, and the PCE of PSCs is 24.04% with a fill factor (FF) of 82.98% and long-term stability. This study underlines the effectiveness of multifunctional additives in improving interface contact and enhancing PCE of PSCs.     

A Fullerene Seeded Strategy for Facile Construction of Nitrogen-Doped Carbon Nano-Onions as Robust Electrocatalysts

Carbon nano-onions (CNOs) as a novel form of carbon materials hold peculiar structural features but their electrocatalytic applications are largely discouraged by the demanding synthesis conditions (e.g., ≥1500 °C and vacuum). Using C₆₀ fullerene molecules as the sacrificial seeds and melamine as the main feedstock, herein, a novel strategy for the facile construction of CNOs nanoparticles is presented with ultrafine sizes (≈5 nm) at relatively low temperatures (≤900 °C) and atmospheric pressure. During the calcination, in-depth characterizations reveal that C₆₀ can retain the melamine-derived graphitic carbon nitride from complete sublimation at high temperatures (≥700 °C). Owing to the N removal and subsequent pentagon generation, severely deformed graphitic fragments together with the disintegrated C₆₀ molecules merge into larger sized nanosheets with high curvature, eventually leading to the formation of N-doped defect-rich CNOs. Owing to the integration of multiple favorable structural features of pentagons, edges, and N dopants, the CNOs obtained at 900 °C present superior oxygen reduction half-wave potential (0.853 V_RHE) and zinc–air cathode performance to the commercial Pt/C (0.838 V_RHE). Density functional theory calculation further uncovers that the carbon atoms adjacent to the N-doped edged pentagons are turned into the ORR-active sites with O₂ protonation as the rate-determining step.     

结合跨层特征融合与级联检测器的防震锤缺陷检测

目的 防震锤可以减少输电线路的周期性震动以降低线路的疲劳损害,定期对防震锤进行巡检非常必要。针对目前无人机巡检输电线路所得航拍图像背景复杂,而种类较多、形状各异以及特性不一的防震锤在航拍图像中占据像素面积很小,导致防震锤检测过程中出现的检测精度低、无法确定缺陷类型等问题,提出了一种结合跨层特征融合和级联检测器的防震锤缺陷检测方法。方法 本文使用无人机对防震锤部件巡检的航拍图像进行数据扩充建立防震锤缺陷检测数据集,并划分了4种缺陷类型,为研究提供了数据基础。首先,以VGG16（Visual GeometryGroup 16-layer network）为基础对1、3、5层特征进行特征融合得到特征图,平衡了语义信息和空间特征;其次,使用3个级联检测器对目标进行分类定位,减小了交并比（intersection over union,IoU）阈值对网络性能的影响;最后,将非极大值抑制法替换为Soft-NMS（soft non-maximum suppression）算法,去除边界框保留了最佳结果。结果 在自建数据集上验证网络模型对4种防震锤缺陷类型的检测效果,与现有基于深度学习的其他6种先进算法相比,本文算法的平均准确率比Fast R-CNN（fast region-based convolutional network）、Faster R-CNN、YOLOv4（you only look onceversion 4）分别提高了13.5%、3.4%、5.8%,比SSD300（single shot MultiBox detector 300）、YOLOv3、RetinaNet分别提高了9.5%、8.5%、8%。与Faster R-CNN相比,本文方法的误检率降低了5.61%,漏检率降低了3.01%。结论 本文提出的防震锤缺陷检测方法对不同背景、不同光照、不同角度、不同尺度、不同种类和不同缺陷种类的防震锤均有较好的检测结果,不但可以更好地提取防震锤的特征,而且还能提高分类和位置预测网络的定位精度,从而有效提高了防震锤缺陷检测算法的准确率,在满足防震锤巡检工作实际检测要求的同时还具有较好的鲁棒性和有效性。     

改进YOLOv5的瓷砖表面缺陷检测

现有瓷砖表面缺陷检测存在识别微小目标缺陷能力不足、检测速度有待提升的问题, 为此本文提出了基于改进YOLOv5的瓷砖表面缺陷检测方法. 首先, 由于瓷砖表面缺陷尺寸偏小的特性, 对比分析YOLOv5s的3个目标检测头分支的检测能力, 发现删除大目标检测头, 只保留中目标检测头和小目标检测头的模型检测效果最佳. 其次, 为了进一步实现模型轻量化, 使用ghost convolution和C3Ghost模块替换YOLOv5s在Backbone网络中的普通卷积和C3模块, 减少模型参数量和计算量. 最后, 在YOLOv5s的Backbone和Neck网络末端添加coordinate attention注意力机制模块, 解决原模型无注意力偏好的问题. 该方法在天池瓷砖瑕疵检测数据集上进行实验, 实验结果表明: 改进后的检测模型的平均精度均值达66%, 相比于原YOLOv5s模型提升了1.8%; 且模型大小只有10.14 MB, 参数量相比于原模型减少了48.7%, 计算量减少了38.7%.     

Lithiation-Induced Defect Engineering to Promote Oxygen Evolution Reaction

Exploring efficient electrocatalysts for oxygen evolution reaction (OER) is an urgent need to advance the development of sustainable energy conversion. Though defect engineering is considered an effective strategy to regulate catalyst activity for enhanced OER performance, the controllable synthesis of defective oxides electrocatalysts remains challenging. Here, oxygen defects are introduced into NiCo₂O₄ nanorods by an electrochemical lithiation strategy. By tuning in situ lithiation potentials, the concentration of oxygen defects and the corresponding catalytic activity can be feasibly regulated. In addition, the relationship between the changes in the defect density and electronic structure and the lithiation cut-off voltages is revealed. The results show that NiCo₂O₄ nanorods undertook intercalation and two-step conversion reaction, in which the lithiation-induced conversion reaction gives rise to a CoO@NiO-based structure with higher defect density and lower oxidation states. As a result, the defective CoO@NiO-based catalyst exhibits exceptional OER activity with an overpotential of 270 mV at 10 mA cm⁻², which is about 74 mV below the pristine nanomaterials. This research proposes a novel strategy to explore high-performance catalysts with structural stability and defect control.     

Passivating Defects of Perovskite Solar Cells with Functional Donor-Acceptor–Donor Type Hole Transporting Materials

In this study, a series of donor–acceptor–donor (D-A-D) type small molecules based on the fluorene and diphenylethenyl enamine units, which are distinguished by different acceptors, as holetransporting materials (HTMs) for perovskite solar cells is presented. The incorporation of the malononitrile acceptor units is found to be beneficial for not only carrier transportation but also defects passivation via Pb–N interactions. The highest power conversion efficiency of over 22% is achieved on cells based on V1359, which is higher than that of spiro-OMeTAD under identical conditions. This st shows that HTMs prepared via simplified synthetic routes are not only a low-cost alternative to spiro-OMeTAD but also outperform in efficiency and stability state-of-art materials obtained via expensive cross-coupling methods.     

面向递增累积型缺陷的灰盒模糊测试变异优化

大量访问越界、内存耗尽、性能故障等缺陷是输入中有效数据的规模过大,超过临界值引起的.而现有灰盒模糊测试技术中的数据依赖识别和变异优化技术大都针对固定规模输入数据格式,对规模递增输入数据的构造效率不高.为此,针对这类累积型缺陷模糊测试对应的状态特征值最优化问题,提出一种对特征值依赖的输入数据的格式判别和差分变异方法.根据引发特征值最值更新的有效变异的位置分布和发现频次特征,判别待发现缺陷状态优化是否依赖于输入中相关数据规模的增长,将引发最值更新的有效变异内容应用于规模递增输入数据生成,提升该类累积型缺陷的复现和定向测试效率.依据该思想,实现了模糊测试工具Jigsaw,在测评实验数据集上的实验结果表明提出的判别方法能够高效地区分特征值依赖的输入数据组织形式,且提出的差分变异方法显著提升了需要大量输入才能触发累积型缺陷的复现效率.