Interface Engineering Enhances the Photovoltaic Performance of Wide Bandgap FAPbBr3 Perovskite for Application in Low-Light Environments

Underwater solar cells (UWSCs) provide an ideal alternative to the energy supply for long-endurance autonomous underwater vehicles. However, different from conventional solar cells situated on land or above water, UWSCs give preference to use wide bandgap semiconductors (≥1.8 eV) as light absorber to match underwater solar spectra. Among wide bandgap semiconductors, FAPbBr₃ perovskite is under prime consideration owing to its matching optical bandgap (≈2.3 eV), outstanding photoelectric properties, easier processability, etc. Unfortunately, for FAPbBr₃ solar cells, substantial interface defects greatly limit the charge carrier extraction efficiency, thus limiting the device performance, especially in underwater low-light environments. This study employs a molecular self-assembly strategy to effectively eliminate the interfacial defects. As a result, a great improvement in power conversion efficiency (PCE) from 6.44% to 7.49% is obtained, which is among the best efficiency reported for inverted FAPbBr₃ solar cells up to date. Besides, a champion PCE of 30% is obtained under 520 nm monochromatic light irradiation (4.8 mW cm⁻²). These results demonstrate that FAPbBr₃ solar cells present a tremendously promising application in UWSCs.     

Synthesis and Characterization of a Low Bandgap Conjugated Polymer for Bulk Heterojunction Photovoltaic Cells

Low optical bandgap conjugated polymers may improve the efficiency of organic photovoltaic devices by increasing the absorption in the visible and near infrared region of the solar spectrum. Here we demonstrate that condensation polymerization of 2,5‐bis(5‐trimethylstannyl‐2‐thienyl)‐N‐dodecylpyrrole and 4,7‐dibromo‐2,1,3‐benzothiadiazole in the presence of Pd(PPh₃)₂Cl₂ as a catalyst affords a novel conjugated oligomeric material (PTPTB), which exhibits a low optical bandgap as a result of the alternation of electron‐rich and electron‐deficient units along the chain. By varying the molar ratio of the monomers in the reaction and fractionation of the reaction product, two different molecular weight fractions (PTPTB‐I and PTPTB‐II, see Experimental section) were isolated, containing 5–17 and 13–33 aromatic units respectively, as inferred from matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS). Thin films of PTPTB‐I and PTPTB‐II exhibit an optical bandgap of 1.60 and 1.46 eV, respectively. Photoinduced absorption (PIA) and photoluminescence spectroscopy of blends of PTPTB‐I and a methanofullerene (1‐(3‐methoxycarbonyl)‐propyl‐1‐phenyl‐[6,6]C₆₁, PCBM) gave direct spectral evidence of the photoinduced electron‐transfer reaction from PTPTB‐I as a donor to the fullerene derivative as an acceptor. Thin PTPTB‐I:PCBM composite films were sandwiched between indium tin oxide/poly(3,4‐ethylenedioxythiophene)/poly(styrene sulfonic acid) (ITO/PEDOT:PSS) and Al electrodes to prepare working photovoltaic devices, which show an open circuit voltage of 0.67 V under white‐light illumination. The spectral dependence of the device shows an onset of the photocurrent at 1.65 eV (750 nm).     

A Low‐Bandgap Semiconducting Polymer for Photovoltaic Devices and Infrared Emitting Diodes

A novel low‐bandgap conjugated polymer (PTPTB, E_g = ∼ 1.6 eV), consisting of alternating electron‐rich N‐dodecyl‐2,5‐bis(2′‐thienyl)pyrrole (TPT) and electron‐deficient 2,1,3‐benzothiadiazole (B) units, is introduced for thin‐film optoelectronic devices working in the near infrared (NIR). Bulk heterojunction photovoltaic cells from solid‐state composite films of PTPTB with the soluble fullerene derivative [6,6]‐phenyl C₆₁ butyric acid methyl ester (PCBM) as an active layer shows promising power conversion efficiencies up to 1 % under AM1.5 illumination. Furthermore, electroluminescent devices (light‐emitting diodes) from thin films of pristine PTPTB show near infrared emission peaking at 800 nm with a turn on voltage below 4 V. The electroluminescence can be significantly enhanced by sensitization of this material with a wide bandgap material such as the poly(p‐phenylene vinylene) derivative MDMO‐PPV.     

Local Field Enhancement Tuning of Horseshoe-Shaped Nanoparticles

We proposed a horseshoe-shaped nano-structure formed by etching a gap on a ring structure. By numerical simulations, it was found that the local field of the structure was significantly enhanced compared with that of the traditional ring structure. Furthermore, an additional resonant peak appeared corresponding to the electric field coupling in the gap, and this resonant wavelength was able to be tuned significantly by the particle size, gap size, and gap position. Such properties make the structure promising in biomedical and sensing applications.     

Tuning Unique Peapod‐Like Co(SxSe1–x)2 Nanoparticles for Efficient Overall Water Splitting

The development of efficient electrocatalysts with low cost and earth abundance for overall water splitting is very important in energy conversion. Although many electrocatalysts based on transition metal dichalcogenides have been developed, rational design and controllable synthesis of fine nanostructures with subtle morphologies and sequential chemical compositions related to these materials remains a challenge. This study reports a series of peapod‐like composites with component‐controllable Co(S_x Se_1–x )₂ nanoparticles encapsulated in carbon fibers, which are obtained by using Co(CO₃)_0.5(OH)·0.11H₂O nanowires as a precursor followed by coating carbon fiber and an adjustable sulfuration/selenylation process. Due to its increased exposure of active sites and improved charge and mass transport capability derived from the unique structure and morphology, the Co(S_x Se_1–x )₂ samples display favorable catalytic activities. It is found that Co(S_0.71Se_0.29)₂ exhibits the best hydrogen evolution reaction (HER) performance and Co(S_0.22Se_0.78)₂ shows the highest activity for the oxygen evolution reaction (OER). When using Co(S_0.71Se_0.29)₂ as a cathode and Co(S_0.22Se_0.78)₂ as an anode, it demonstrates a durable activity for overall water splitting to deliver 10 mA cm^?2 at a cell voltage of 1.63 V, thus offering an attractive cost‐effective earth abundant material system toward water splitting.     

Enhanced Hole-Carrier Selectivity in Wide Bandgap Halide Perovskite Photovoltaic Devices for Indoor Internet of Things Applications

Halide perovskite-based photovoltaic (PV) devices have recently emerged for low energy consumption electronic devices such as Internet of Things (IoT). In this work, an effective strategy to form a hole-selective layer using phenethylammonium iodide (PEAI) salt is presented that demonstrates unprecedently high open-circuit voltage of 0.9 V with 18 µW cm⁻² under 200 lux (cool white light-emitting diodes). An appropriate post-deposited amount of PEAI (2 mg) strongly interacts with the perovskite surface forming a conformal coating of PEAI on the perovskite film surface, which improves the crystallinity and absorption of the film. Here, Kelvin probe force microscopy results indicate the diminished potential difference across the grain boundaries and grain interiors after the PEAI deposition, constructing an electrically and chemically homogeneous surface. Also, the surface becomes more p-type with a downshift of a valence band maximum, confirmed by ultraviolet photoelectron spectroscopy measurement, facilitating the transport of holes to the hole transport layer (HTL). The hole-selective layer-deposited devices exhibit reduced hysteresis in light current density–voltage curves and maintain steadily high fill factor across the different light intensities (200–1000 lux). This work highlights the importance of the HTL/perovskite interface that prepares the indoor halide perovskite PV devices for powering IoT device.     

Tuning of the Photovoltaic Parameters of Molecular Donors by Covalent Bridging

The synthesis of donor‐acceptor molecules involving triarylamines and dicyanovinyl blocks is described. Optical and electrochemical results show that rigidification of the acceptor part of the molecule by a covalent bridge leads to a ca. 0.20 eV increase of the band gap due to a parallel increase of the lowest unoccupied molecular orbital level. A preliminary evaluation of these compounds as donor materials in organic solar cells shows that although this structural modification reduces the light‐harvesting properties of the donor molecule, it nevertheless induces an increase of the efficiency of the resulting solar cells due to a simultaneous improvement of the open‐circuit voltage and fill factor.     

Tuning the Polarizability in Donor Polymers with a Thiophenesaccharin Unit for Organic Photovoltaic Applications

This paper describes the synthesis of low bandgap copolymers incorporating an artificial sweetener derivative, N‐alkyl, 3‐oxothieno[3,4‐d]isothiazole 1,1‐dioxide (TID). This new TID unit is identical to the well‐known thieno[3,4‐c]pyrrole‐4,6‐dione (TPD) unit except that one carbonyl has been replaced by a sulfonyl group. Semi‐empirical calculations on the local dipole moment change between ground and excited states (Δμ_ge) in the repeating units of the new polymer indicate that the replacement of the carbonyl by a sulfonyl group leads to larger Δμ_ge values. The resulting polymers exhibit a diminished power‐conversion efficiency (PCE) compared to a bulk heterojunction (BHJ) solar cells with PC₇₁BM as an acceptor, which extends the correlation between PCE and Δμ_ge of single repeating units in p‐type polymers to a new regime. Detailed studies show that the strongly electron‐withdrawing sulfonyl group is detrimental to charge separation in alternating copolymers containing a TID unit.     

Tuning the Bandgap Character of Quantum‐Confined Si–Sn Alloyed Nanocrystals

Nanocrystals in the regime between molecules and bulk give rise to unique electronic properties. Here, a thorough study focusing on quantum‐confined nanocrystals (NCs) is provided. At the level of density functional theory an approximate (quasi) band structure which addresses both the molecular and bulk aspects of finite‐sized NCs is calculated. In particular, how band‐like features emerge with increasing particle diameter is shown. The quasiband structure is used to discuss technological‐relevant direct bandgap NCs. It is found that ultrasmall Sn NCs have a direct bandgap in their at‐nanoscale‐stable α‐phase and for high enough Sn concentration (≈41%) alloyed Si–Sn NCs transition from indirect to direct bandgap semiconductors. The calculations strongly support recent experiments suggesting a direct bandgap for these systems. For a quantitative comparison many‐body GW + Bethe–Salpeter equation (BSE) calculations are performed. The predicted optical gaps are close to the experimental data and the calculated absorbance spectra compare well with the corresponding measurements.     

Tuning the Electronic Bandgap of Graphdiyne by H-Substitution to Promote Interfacial Charge Carrier Separation for Enhanced Photocatalytic Hydrogen Production

Graphdiyne (GDY), which features a highly π-conjugated structure, direct bandgap, and high charge carrier mobility, presents the major requirements for photocatalysis. Up to now, all photocatalytic studies are performed without paying too much attention on the GDY bandgap (1.1 eV at the G₀W₀ many-body theory level). Such a narrow bandgap is not suitable for the band alignment between GDY and other semiconductors, making it difficult to achieve efficient photogenerated charge carrier separation. Herein, for the first time, it is demonstrated that tuning the electronic bandgap of GDY via H-substitution (H-GDY) promotes interfacial charge separation and improves photocatalytic H₂ evolution. The H-GDY exhibits an increased bandgap energy ( ≈ 2.5 eV) and exploitable conduction band minimum and valence band maximum edges. As a representative semiconductor, TiO₂ is hybridized with both H-GDY and GDY to fabricate a heterojunction. Compared to the GDY/TiO₂, the H-GDY/TiO₂ heterojunction leads to a remarkable enhancement of the photocatalytic H₂ generation by 1.35 times under UV–visible illumination (6200 µ mol h⁻¹ g⁻¹) and four times under visible light (670 µ mol h⁻¹ g⁻¹). Such enhancement is attributed to the suitable band alignment between H-GDY and TiO₂, which efficiently promotes the photogenerated electron and hole separation, as supported by density functional theory calculations.     

一种高精度曲率补偿带隙基准电压电路

设计一种采用电流模式和Buck’s电压转移单元对VBE进行高阶补偿的带隙基准电压源。电路采用CSMC0．5μm DPTM CMOS工艺制造。温度在-40～125℃之间变化时,基准电压源的温度系数为3．15ppm／℃,在3．5～5．0V之间的电压调整率为0．35mV／V。     

Tuning the Morphology and Performance of Low Bandgap Polymer:Fullerene Heterojunctions via Solvent Annealing in Selective Solvents

Low bandgap polymer (LBG):fullerene mixtures are some of the most promising organic photovoltaic active layers. Unfortunately, there are no post‐deposition treatments available to rationally improve the morphology and performance of as‐cast LBG:fullerene OPV active layers, where thermal annealing usually fails. Therefore, there is a glaring need to develop post‐deposition methods to guide the morphology of LBG:fullerene bulk heterojunctions towards targeted structures and performance. In this paper, the structural evolution of PCPDTBT:PCBM mixtures with solvent annealing (SA) is examined, focusing on the effect of solvent quality of the fullerene and polymer in the annealing vapor on morphological evolution and device performance. The results indicate that exposure of this active layer to the solvent vapor controls the ordering of PCPDTBT and PCBM phase separation very effectively, presumably by inducing component mobility as the solvent plasticizes the mixture. These results also unexpectedly indicate that solvent annealing in a selective solvent provides a method to invert the morphology of the LBG:fullerene mixture from a polymer aggregate dispersed in a polymer:fullerene matrix to fullerene aggregates dispersed in a polymer:fullerene matrix. The judicious choice of solvent vapor, therefore, provides a unique method to exquisitely control and optimize the morphology of LBG conjugated polymer/fullerene mixtures.     

压电音叉及其应用

介绍了压电音叉的基本结构和等效电路,详细描述了压电音叉的工作原理以及各种实际应用,并对实际产品的选材及性能作了详细的介绍。作者还根据自己的研究结果介绍了几种实用的和用作压电音叉换能元件的压电陶瓷材料的配方。     

Tuning Dichroic Plasmon Resonance Modes of Gold Nanoparticles in Optical Thin Films

A simple method is presented to tune the gold surface plasmon resonance (SPR) modes by growing anisotropic nanoparticles into transparent SiO₂ thin films prepared by glancing angle deposition. In this type of composite film, the anisotropy of the gold nanoparticles, proved by gracing incidence small angle X‐ray scattering, is determined by the tilted nanocolumnar structure of the SiO₂ host and yields a strong film dichroism evidenced by a change from an intense colored to a nearly transparent aspect depending on light polarization and/or sample orientation. The formation in these films of lithographic non‐dichroic SPR patterns by nanosecond laser writing demonstrates the potentialities of this procedure to develop novel optical encryption or anti‐counterfeiting structures either at micrometer‐ or macroscales.     

Enhanced Structural Stability and Performance Durability of Bulk Heterojunction Photovoltaic Devices Incorporating Metallic Nanoparticles

Despite the progress on organic photovoltaic (OPV) performance, the photoactive layer degradation during prolonged solar illumination is still a major obstacle. In this work, an approach to mitigate the degradation pathway related to structural/morphological changes of the photoactive layer occurring upon continuous illumination in air is presented. It is shown, for the first time, that the incorporation of Ag nanoparticles in poly(3‐hexylthiophene) (P3HT) and [6‐6]‐phenyl‐C61‐butyric acid methyl ester bulk heterojunction (BHJ) leads to improved structural and morphological properties of the composite BHJ solar cells and to better photovoltaic (PV) stability after long periods of continuous illumination. This is evidenced by an original approach based on joint in‐situ time‐resolved X‐ray and atomic force microscopy monitoring. Besides the structural stability improvement and reduced photodegradation rate, it is shown that the composite blends exhibit superior PV performance compared to the pristine BHJs. It can be postulated that the incorporation of metallic nanoparticles in the BHJ leads to a dual enhancement, a plasmon absorption mediated effect, causing improved initial cell efficiency, and a structural stability effect giving rise to reduced degradation rate upon prolonged illumination. The results are in favor of the exploitation of polymer–nanoparticle composites as a promising approach to mitigate the aging effects in OPVs.     

钐钴永磁材料在行波管中的应用

介绍了行波管中永磁材料的选择，Sm2Co17型永磁材料的稳定性，以及测试中极靴、极靴厚度和外径对磁场的影响等。与其它永磁材料相比，Sm2Co17型永磁材料稳定性好，是一种理想的行波管聚焦磁性材料；实验表明：磁环两端加上极靴后，轴向磁场将得到提高，而且极靴外径对磁场的影响比厚度大。     

对有源相控阵雷达的一些新要求与宽禁带半导体器件的应用（续完）

FPFM，场效应晶体管(FET)功率处理能力(FET power handling capacity)的品质因素     

Co3O4-TiO2纳米颗粒制备及光催化性能研究

面对日益增长的能源需求,开发绿色新能源成为当前的研究热点。模拟自然界光合作用在太阳光的照射下利用半导体纳米材料作为光催化剂分解水制备H2的人工光合作用受到了越来越多的关注。但是单用TiO2或者Co3O4作催化剂时,其化学稳定性极差,具有强烈的吸附其他粒子以达到稳定状态的趋向,造成纳米粒子的团聚,最终导致在实际使用时不能充分地发挥它的纳米特性。因而,纳米复合材料的研究势在必行。选用N 型半导体TiO2纳米材料与P型半导体Co3O4复合,制备出具有P-N结的Co3O4-TiO2半导体纳米颗粒。并搭建了光解水平台进行实验,Co3O4-TiO2半导体复合材料被模拟太阳光激发完全分解纯水生成H2和O2的效率分别为0.163μmol/h和0.08μmol/h,氢气和氧气生成量的比约为2:1。     

对有源相控阵雷达的一些新要求与宽禁带半导体器件的应用

讨论对有源相控阵雷达和T／R组件的一些新要求。宽禁带半导体材料与器件的主要性能与特点在文中作了简要介绍。宽禁带半导体器件在有源相控阵雷达中的潜在应用在文中也进行了讨论。