Novel CMOS image sensor pixel to improve charge transfer speed and efficiency by overlapping gate and temporary storage diffusing node

A novel CMOS image sensor(CIS) pinned photodiode(PPD) pixel, named as O-T pixel, is proposed and investigated by TCAD simulations. Compared with the conventional PPD pixel, the proposed pixel features the overlapping gate(OG)and the temporary storage diffusing(TSD) region, based on which the several-nanosecond-level charge transfer could be achieved and the complete charge transfer from the PPD to the floating node(FD) could be realized. And systematic analyses of the influence of the doping conditions of the proposed processes, the OG length, and the photodiode length on the transfer performances of the proposed pixel are conducted. Optimized simulation results show that the total charge transfer time could reach about 5.862 ns from the photodiode to the sensed node and the corresponding charge transfer efficiency could reach as high as 99.995% in the proposed pixel with 10 μm long photodiode and 2.22 μm long OG. These results demonstrate a great potential of the proposed pixel in high-speed applications.

Recent strategies to enhance the efficiency of hematite photoanodes in photoelectrochemical water splitting

Photoelectrochemical(PEC)water splitting is one of the most promising approaches toward achieving the conversion of solar energy to hydrogen.Hematite is a widely applied photoanode material in PEC water splitting because of its appropriate band structure,non-toxicity,high stability,and low cost.Nevertheless,its relatively low photochemical conversion efficiency limits its application,and enhancing its PEC water splitting efficiency remains a challenge.Consequently,increasing efforts have been rendered toward improving the performance of hematite photoanodes.The entire PEC water splitting efficiency typically includes three parts:the photon absorption efficiency,the separation efficiency of the semiconductor bulk,and the surface injection efficiency.This review briefly discusses the recent advances in studies on hematite photoanodes for water splitting,and through the enhancement of the three above-mentioned efficiencies,the corresponding strategies toward improving the PEC performance of hematite are comprehensively discussed and summarized.

Influence of sub-bandgap illumination on space charge distribution in CdZnTe detector

The space charge accumulation in CdZnTe crystals seriously affects the performance of high-flux pulse detectors.The influence of sub-bandgap illumination on the space charge distribution and device performance in CdZnTe crystals were studied theoretically by Silvaco TCAD software simulation.The sub-bandgap illumination with a wavelength of 890 nm and intensity of 8×10−8 W/cm2 were used in the simulation to explore the space charge distribution and internal electric field distribution in CdZnTe crystals.The simulation results show that the deep level occupation faction is manipulated by the sub-bandgap illumination,thus space charge concentration can be reduced under the bias voltage of 500 V.A flat electric field distribution is obtained,which significantly improves the charge collection efficiency of the CdZnTe detector.Meanwhile,premised on the high resistivity of CdZnTe crystal,the space charge concentration in the crystal can be further reduced with the wavelength of 850 nm and intensity of 1×10−7 W/cm2 illumination.The electric field distribution is flatter and the carrier collection efficiency of the device can be improved more effectively.

Review on heterophase/homophase junctions for efficient photocatalysis: The case of phase transition construction

Semiconductor photocatalysts are extensively applied in environmental treatment and energy conversion.However,one of their major disadvantages is their relatively low photocatalytic performance owing to the recombination of generated electron-hole pairs.The presence of the phase junction is an effective way to promote the photocatalytic activity by increasing the separation efficiency of the electron-hole pairs.Accordingly,extensive research has been conducted on the design of phase junctions of photocatalysts to improve their charge transfer properties and efficiencies.Therefore,for the design of an appropriate phase junction and the understanding of the mechanism of electron-hole separation,the development of the photocatalytic phase junction,including the preparation methods of the heterogeneous materials,is tremendously important and helpful.Herein,the commonly used,externally induced phase transformation fabrication techniques and the primary components of the semiconductors are reviewed.Future directions will still focus on the design and optimization of the phase junction of photocatalytic materials according to the phase transition with higher efficiencies for broadband responses and solar energy utilization.Additionally,the most popular phase transformation fabrication techniques of phase junctions are briefly reviewed from the application viewpoint.

A molecular cobaloxime cocatalyst and ultrathin FeOOH nanolayers co-modifiedBiVO_(4) photoanode for efficient photoelectrochemical water oxidation

BiVO_(4) has been attracting a lot of interest in photoelectrochemical (PEC) water oxidation due to its efficient solar absorption and appropriate band positions.So far,sluggish water oxidation kinetics and fast photogenerated charge recombination still hinder the PEC performance ofBiVO_(4) .In this study,a novel PEC photoanode was designed by depositing ultrathin FeOOH nanolayers on the surface of nanoporousBiVO_(4) electrode,followed by modification with a cobaloxime (Co(dmgH)_(2)(4-COOH-py)Cl) molecular cocatalyst.Under irradiation of a 100 mW cm^(-2)(AM 1.5G) Xe lamp,the photocurrent density of the cobaloxime/FeOOH/BiVO_(4) composite photoanode reached 5.1 mA cm^(-2)at 1.23 V vs.RHE in 1.0 M potassium borate buffer solution (pH=9.0).The onset potential of the optimal cobaloxime/FeOOH/BiVO_(4) photoanode exhibited a 460 m V cathodic shift relative to bareBiVO_(4) .In addition,the surface charge injection efficiency of the composite photoanode reached~80%at 1.23 V vs.RHE and the incident photon-to-current efficiency (IPCE) reached~88%at 420 nm.

Charge transfer efficiency improvement of a 4-T pixel by the optimization of electrical potential distribution under the transfer gate

The charge transfer efficiency improvement method is introduced by optimizing the electrical potential distribution under the transfer gate along the charge transfer path. A non-uniform doped transfer transistor chan- nel is introduced to provide an ascending electrical potential gradient in the transfer transistor channel. With the adjustments to the overlap length between the R1 region and the transfer gate, the doping dose of the R1 region, and the overlap length between the anti-punch-through （APT） implantations and transfer gate, the potential barrier and potential pocket in the connecting region of transfer transistor channel and the pinned photodiode （PPD） are reduced to improve the electrical potential connection. The simulation results show that the percentage of residual charges to total charges drops from 1/10^4 to 1/10^7, and the transfer time is reduced from 500 to 110 ns. This means the charge transfer efficiency is improved.

Highly enhanced visible-light photocatalytic hydrogen evolution on g-C_3N_4 decorated with vopc through π-π interaction

Photocatalytic H2 evolution reactions on pristine graphitic carbon nitrides(g-C3N4),as a promising approach for converting solar energy to fuel,are attractive for tackling global energy concerns but still suffer from low efficiencies.In this article,we report a tractable approach to modifying g-C3N4 with vanadyl phthalocyanine(VOPc/CN)for efficient visible-light-driven hydrogen production.A non-covalent VOPc/CN hybrid photocatalyst formed viaπ-πstacking interactions between the two components,as confirmed by analysis of UV-vis absorption spectra.The VOPc/CN hybrid photocatalyst shows excellent visible-light-driven photocatalytic performance and good stability.Under optimal conditions,the corresponding H2 evolution rate is nearly 6 times higher than that of pure g-C3N4.The role of VOPc in promoting hydrogen evolution activity was to extend the visible light absorption range and prevent the recombination of photoexcited electron-hole pairs effectively.It is expected that this facile modification method could be a new inspiration for the rational design and exploration of g-C3N4-based hybrid systems with strong light absorption and high-efficiency carrier separation.

Photoelectrochemical evaluation of SILAR-deposited nanoporous BiVO4 photoanodes for solar-driven water splitting

We report a photoelectrochemical investigation of BiVO4 photoanodes prepared by successive ionic layer adsorption and reaction(SILAR),a facile method that yields uniform nanoporous films.After characterization of the phase,morphology,composition,and optical properties of the prepared films,the efficiencies of charge separation(ηsep)and water oxidation(ηox)in solar water splitting cells employing these photoanodes were estimated following a previously reported procedure.Unexpected wavelength and illumination direction dependencies were discovered in the derived efficiencies,casting doubt on the validity of the analysis.An alternative approach using a diffusion–reaction model that explicitly considers the efficiency of electron collection resolved the discrepancies and explained the illumination direction dependence of the photocurrent.Electron diffusion lengths(Ln)of 0.45μm and 0.55μm were derived for pristine and cobalt phosphate(Co-Pi)modified BiVO4,respectively,which are much shorter than the film thickness of^2.1μm.The Co-Pi treatment also increasedηoxfrom 0.86 to^1,which is the main reason for the overall performance enhancement caused by adding Co-Pi.These findings suggest that there is little scope for improving the performance of SILAR-deposited BiVO4 photoanodes by further catalyzing water oxidation,but enhanced performance is achievable if electron transport can be improved.

Progress in hole-transporting materials for perovskite solar cells

In recent years the photovoltaic community has witnessed the unprecedented development of perovskite solar cells（PSCs） as they have taken the lead in emergent photovoltaic technologies. The power conversion efficiency of this new class of solar cells has been increased to a point where they are beginning to compete with more established technologies. Although PSCs have evolved a variety of structures, the use of hole-transporting materials（HTMs） remains indispensable. Here, an overview of the various types of available HTMs is presented. This includes organic and inorganic HTMs and is presented alongside recent progress in associated aspects of PSCs, including device architectures and fabrication techniques to produce high-quality perovskite films. The structure, electrochemistry, and physical properties of a variety of HTMs are discussed, highlighting considerations for those designing new HTMs. Finally, an outlook is presented to provide more concrete direction for the development and optimization of HTMs for highefficiency PSCs.

Layered-stacking of titania films for solar energy conversion:Toward tailored optical,electronic and photovoltaic performance

Nanostructured TiO2 with differentiate morphologies has attracted tremendous attention due to its wide band-gap nature as well as outstanding optical and electric properties for solar-driven light-toelectricity conversion application. Layered-stacking TiO2 film such as double-layer, tri-layer, quadrupleor quintuplicate-layer, is highly desirable to the design of high-performance semiconductor material photoanodes and the development of advanced photovoltaic devices. In this minireview, we will summarize the recent progress and achievements on proof-of-concept of layered-stacking TiO2 films（LTFs） for solar cells with emphasis on the tailored properties and synergistic functionalization of LTFs, such as optimized sensitizer adsorption, broadened light confinement as well as facilitated electron transport characteristics.Various demonstrations of LTFs photovoltaic systems provide lots of possibilities and flexibilities for more efficient solar energy utilization that a wide variety of TiO2 with distinguished morphologies can be integrated into differently structured photoanodes with synergistic and complementary advantages. This key structure engineering technology will also pave the way for the development of next generation state-ofthe-art electronics and optoelectronics. Finally, from our point of view, we conclude the future research interest and efforts for constructing more efficient LTFs as photoelectrode, which will be highly warranted to advance the solar energy conversion process.

Preparation of TiO2 Nanocrystals/Graphene Composite and Its Photocatalytic Performance

TiO2 nanocrystals/graphene （TiO2/GR） composite are prepared by combining flocculation and hydrothermal reduction technology using graphite oxide and TiO2 colloid as precursors. The obtained materials are examined by scanning electron microscopy, transition electron microscopy, X-ray diffraction, N2 adsorption desorption, and ultraviolet-visible diffuse spectroscopy. The results suggest that the presence of TiO2 nanocrystals with diameter of about 15 nm prevents GR nanosheets from agglomeration. Owing to the uniform distribution of TiO2 nanocrystals on the GR nanosheets, TiO2/GR composite exhibits stronger light absorption in the visible region, higher adsorption capacity to methylene blue and higher efficiency of charge separation and transportation compared with pure TiO2. Moreover, the TiO2/GR composite with a GR content of 30% shows higher photocatalytic removal efficiency of MB from water than that of pure TiO2 and commercial P25 under both UV and sunlight irradiation.

高功率密度外延的单晶金刚石制备高性能辐射探测器

辐射探测器是用来研究超宽禁带半导体金刚石中载流子动力学的重要表征工具.本文采用微波等离子体化学气相沉积(MPCVD)方法在高温高压(HTHP)金刚石衬底上制备了高质量的单晶金刚石.我们通过压缩等离子体球来提高微波功率密度,优化了等离子体中的碳氢(C/H)比,并显著降低了金刚石外延层中的杂质和位错含量.(004)面X射线衍射摇摆曲线的半高宽(FWHM)仅为15弧秒,在室温下的光致发光光谱中没有检测到杂质发光带.使用制备的200μm厚的外延金刚石膜制成的辐射探测器可对α-粒子响应,其电子的电荷收集效率为97.03%,能量分辨率为2.1%,空穴的电荷收集效率和能量分辨率为97.86%和1.5%.此外,电子和空穴的迁移率和寿命的乘积分别达到8×10^(−5)和4.1×10^(−4) cm^(2) V^(−1).此方法有望满足商用金刚石辐射探测器对性能和成本控制的严苛要求.

Charged ultrafine particle filtration through vehicular cabin air filters

Understanding the effectiveness of cabin air filters is important for assessing human exposure to ultra- fine particles （UFPs） of vehicular origin. The filtration efficiency of vehicular UFPs with electric charges was investigated for different electric charge characteristics （charge state, charge polarity）. The average filtration efficiency increased ~10% as the electric charge state on the particles changed in distribution from lightly charged to highly charged. The enhancement of filtration efficiency due to electric charge was different at various filter-face air velocities. As electric charges increased, the filtration efficiency increased 12% and 9% at low air velocity （0.1 m/s） and high air velocity （0.S m/s）, respectively. The filter fiber material poses somewhat effect on the filtration efficiency change due to the electric charge. The effects of filter usage and charge polarity on filtration efficiency due to the electric charge were negligi- ble. A coefficient was empirically derived and successfully accounts for the electric charge effect on UFP filtratinn efficiency.

High voltage generator circuit with low power and high efficiency applied in EEPROM

This paper presents a low power and high efficiency high voltage generator circuit embedded in electrically erasable programmable read-only memory（EEPROM）.The low power is minimized by a capacitance divider circuit and a regulator circuit using the controlling clock switch technique.The high efficiency is dependent on the zero threshold voltage（V_（th）） MOSFET and the charge transfer switch（CTS） charge pump.The proposed high voltage generator circuit has been implemented in a 0.35μm EEPROM CMOS process.Measured results show that the proposed high voltage generator circuit has a low power consumption of about 150.48μW and a higher pumping efficiency（83.3%） than previously reported circuits.This high voltage generator circuit can also be widely used in low-power flash devices due to its high efficiency and low power dissipation.

Influence of Extraction Barrier on the Loss Process of Photogenerated Charge Carrier in Polymer Bulk Heterojunction Solar Cells

Based on a full device model adopting three-dimensional Pauli master equation approach, the charge carrier loss process due to poor extraction channels between electrode and active layer in polymer bulk heterojunction（BHJ） solar cells was studied. The influence of barrier height on device performance was simulated to reveal the importance of electrode improvement. It was found that relatively large extraction barrier height（over 0.40 eV） can lead to the significant diminishing of the overall charge collection efficiency, since bimolecular recombination rate would increase to a high level due to enhanced space charge accumulation effect near electrodes. In contrast, the percentage of charge carrier annihilated due to geminate recombination did not change significantly with barrier height variation. Our simulation results may provide the basis for a more accurate model and potential direction of polymer BHJ solar cells improvement.

D-A structured high efficiency solid luminogens with tunable emissions： Molecular design and photophysical properties

Fabrication of efficient solid luminogens with tunable emission is both fundamentally significant and technically important. Herein, based on our previous strategy for the construction of efficient and multifunctional solid luminogens through the combination of diverse aggregation-induced emission （ALE） units with other functional moieties, a group of luminophores with electron donor-acceptor （D-A） structure and typical intramolecular charge transfer （ICT） characteristics, namely CZ-DCDPP, DPA-DCDPP and DBPA-DCDPP were synthesized and investigated. The presence of twisting and AlE-active 2,3- dicyano-S,6-diphenylpyrazine （DCDPP） moiety endows them highly emissive in the solid states, whereas the introduction of arylamines with varied electron-donating capacity and different conjugation render them with tunable solid emissions from green to red. While CZ-DCDPP and DPA-DCDPP solids exhibit distinct mechanochromism, both DPA-DCDPP and DBPA-DCDPP solids can generate efficient red emission. Owing to their high efficiency, remarkable thermal and morphological stabilities and moreover red emission, they are promising for diverse optoelectronic and biological applications.

Energy Management Strategy for Hybrid Electric Vehicle Based on System Efficiency and Battery Life Optimization

A novel method to calculate fuel-electric conversion factor for full hybrid electric vehicle（HEV）equipped with continuously variable transmission（CVT）is proposed.Based on consideration of the efficiency of pivotal components,electric motor,system efficiency optimization models are developed.According to the target of instantaneous optimization of system efficiency,operating ranges of each mode of power-train are determined,and the corresponding energy management strategies are established.The simulation results demonstrate that the energy management strategy proposed can substantially improve the vehicle fuel economy,and keep battery state of charge（SOC）change in a reasonable variation range.

An ultrafast carrier dynamics system from oxygen vacancies modified SnO_(2)QDs and Zn_(2)SnO_(4)heterojunction for deeply photocatalytic oxidation of NO

Deeply photocatalytic oxidation of NO-to-NO_(3)holds great promise for alleviating NO_(x) pollution.The major challenge of NO photo-oxidation is the highly in-situ generated NO_(2) concentration,and the formation of unstable nitrate species causes desorption to release NO_(2).In this study,SnO_(2) quantum dots and oxygen vacancies co-modified Zn_(2)SnO_(4)(ZSO-SnO_(2)-OVs)were prepared by a one-step hydrothermal procedure,the NO photo-oxidation was investigated by a combination of solid experimental and theoretical support.Impressively,spectroscopic measurements indicate that fast carrier dynamics can be achieved due to the electron transfer efficiency of ZSO-SnO_(2)-OVs reaching 99.99%,far outperforming the counterpart and previously reported photocatalysts.During NO oxidation,molecular NO/O_(2) and H2O are efficiently adsorbed/activated around OVs and SnO_(2) QDs,respectively.In-situ infrared measurements and calculated electron localized function disclose two main findings:(1)richly electrons enable NO promptly form NOinstead of toxic NO_(2) or NO^(+);(2)the generation of stable and undecomposed bidentate NO_(3)rather than bridging or monodentate one benefits the deep oxidation of NO via shifting reaction sites from O terminals for original ZSO to Sn ones for ZSO-SnO_(2)-OVs.The synergistic action of SnO_(2) QDs and OVs positively contributes to the NO oxidation performance enhancement(60.6%,0.1 g of sample)and high selectivity of NO to NO_(3)(99.2%).Results from this study advance the mechanistic understanding of NO photooxidation and its selectivity to NO_(3)over photocatalysts.