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Abstract To achieve high power conversion efficiency in perovskite/silicon tandem solar cells, it is necessary to develop a promising wide-bandgap perovskite absorber and processing techniques in relevance. To date, the performance of devices based on wide-bandgap perovskite is still limited mainly by carrier recombination at their electron extraction interface. Here, we demonstrate assembling a binary two-dimensional perovskite by both alternating-cation-interlayer phase and Ruddlesden−Popper phase to passivate perovskite/C60 interface. The binary two-dimensional strategy takes effects not only at the interface but also in the bulk, which enables efficient charge transport in a wide-bandgap perovskite solar cell with a stabilized efficiency of 20.79% (1 cm2). Based on this absorber, a monolithic perovskite/silicon tandem solar cell is fabricated with a steady-state efficiency of 30.65% assessed by a third party. Moreover, the tandem devices retain 96% of their initial efficiency after 527 h of operation under full spectral continuous illumination, and 98% after 1000 h of damp-heat testing (85 °C with 85% relative humidity).

Abstract The long‐term stability issue of halide perovskite solar cells hinders their commercialization. The residual stress–strain affects device stability, which is derived from the mismatched thermophysical and mechanical properties between adjacent layers. In this work, we introduced the Rb2CO3 layer at the interface of SnO2/perovskite with the hierarchy morphology of snowflake‐like microislands and dendritic nanostructures. With a suitable thermal expansion coefficient, the Rb2CO3 layer benefits the interfacial stress relaxation and results in a compressive stress–strain in the perovskite layer. Moreover, reduced nonradiative recombination losses and optimized band alignment were achieved. An enhancement of open‐circuit voltage from 1.087 to 1.153 V in the resultant device was witnessed, which led to power conversion efficiency (PCE) of 22.7% (active area of 0.08313 cm2) and 20.6% (1 cm2). Moreover, these devices retained 95% of its initial PCE under the maximum power point tracking (MPPT) after 2700 h. It suggests inorganic materials with high thermal expansion coefficients and specific nanostructures are promising candidates to optimize interfacial mechanics, which improves the operational stability of perovskite cells.

Abstract Considering the limited information sharing between natural gas systems (NGS) and electrical power systems (EPS), this paper proposes a distributed resilience assessment method for NGS and EPS. First, a coordinated restoration framework is presented for incompletely integrated energy systems, and the collaborative benefit redistribution mechanism is proposed to motivate the participation of the cooperative restoration. Then fragility and recovery models for NGS and EPS components are developed, involving the impact of wind and rainfall during typhoons. An emergency load shedding model considering the conditional value at risk under typhoons is built, where the dynamic constraints of gas storage in NGS's pipelines is considered, and a linear approximation method is adopted to make the solution feasible. The modified alternating direction method of multipliers algorithm is used to solve the problem, and herein the self‐adaptive penalty factor is leveraged to boost the efficiency. Based on the valley‐shaped resilience model, the concept of skewness and kurtosis are introduced to give risk‐adverse metrics more systematically to the impact of extreme events. The proposed model and algorithm are validated by case studies. Except for the performance exploration, the weakness and enhancement suggestions are also concluded from the case analysis.

For the purpose of assessing the transient voltage stability of renewable energy grid more effectively and to measure the epistemic uncertainty of the evaluation results, a power system transient voltage stability assessment method based on residual stochastic differential equation network (SDE-Net) is proposed in this paper. Considering the transient stability characteristics is chronological, the proposed network takes the time series of the basic physical quantity measurement data of the power system as the input. The internal features of time series data are extracted by residual convolution block based stochastic differential equation network in this paper. Meanwhile, the proposed method introduces the focal loss function to eliminate the imbalance of the samples and improve the accuracy of transient stability assessment. In particular, the drift network for learning prediction of stability and the diffusion network for learning uncertainty measurement in residual SDE-Net are trained respectively. As a result, case study on modified IEEE 30- bus system demonstrate the residual SDE-Net’s superior performances on both transient voltage stability assessment and stability evaluation result confidence estimation.

Abstract Driven by the urgent need for adaptive infrared (IR) electrochromic devices, the improvement in electrochromic performance based on polyaniline (PANI) conducting polymers has become an outstanding challenge. In recent years, the acid doping strategy has been proven to increase the IR modulation ability of PANI, in particular for the Bronsted acid doping. Herein, the effects of copper ions, a Lewis acid, on the structure and electrochromic properties of polyaniline were investigated. Compared to pure polyaniline, the Cu-doped PANI porous films show better IR modulation ability. With the increasing concentration of copper ions, the Cu-doped PANI porous films exhibit a trend in volcanic patterns for the emittance variation (∆ε), depending on the number of polarons and bipolarons. The optimal IR emissivity (ε) modulation obtained on Cu-doped PANI films shows the ∆ε modulation of 0.35 and 0.3 in the wavelength range of 8–14 µm and 2.5–25 µm, superior to previously reported pure sulfuric acid-doped PANI. Furthermore, a flexible IR electrochromic device was fabricated with the present Cu-doped PANI porous films. The modulation of the emittance variation varied between 0.513 and 0.834 (∆ε = 0.32 in ranges of wavelength 8–12 µm), suggesting the great potential for applications in military camouflage and intelligent IR thermal management. We believe that the results in this work will provide a novel perspective and avenue for improving the IR modulation ability of electrochromic devices based on polyaniline conducting polymers.

Abstract Background Increasing studies have revealed that circular RNAs (CircRNAs) make great contributions to regulating tumor progression. Therefore, we intended to explore the expression characteristics, function, and related mechanisms of a novel type of circRNA, PIP5K1A, in glioma. Methods Firstly, reverse transcription-polymerase chain reaction (RT-PCR) was carried out to examine CircPIP5K1A expression in glioma tissues and adjacent normal tissues, and the correlation between CircPIP5K1A level and the clinical-pathological indicators of glioma was analyzed. Then, the CircPIP5K1A expression in various glioma cell lines was detected, and CircPIP5K1A overexpression and knockdown cell models were constructed. Subsequently, cell proliferation and viability were detected by the CCK8 method and BrdU staining. Cell apoptosis was detected by flow cytometry, and cell invasion was examined by Transwell assay. The expression of TCF12, PI3K/AKT pathway apoptotic related proteins (Caspase3, Bax, and Bcl2) and epithelial-mesenchymal transition (EMT) markers (E-cadherin, Vimentin, and N-cadherin) was determined by western blot or RT-PCR. Results The results manifested that CircPIP5K1A was upregulated in glioma tissues (compared with that in normal adjacent tissues), and overexpressed CircPIP5K1A was related to glioma volume and histopathological grade. Functionally, overexpressing CircPIP5K1A notably elevated glioma cell proliferation, invasion, and EMT and inhibited apoptosis both in vivo and in vitro. Besides, CircPIP5K1A upregulated TCF12 and PI3K/AKT activation. Bioinformatics analysis testified that miR-515-5p was a common target of CircPIP5K1A and TCF12, while the dual-luciferase reporter assay and RNA immunoprecipitation (RIP) experiment further confirmed that CircPIP5K1A targeted miR-515-5p, which bound the 3′-untranslated region (UTR) of TCF12. Conclusions Overall, the study illustrated that CircPIP5K1A is a potential prognostic marker in glioma and regulates glioma evolvement by modulating the miR-515-5p-mediated TCF12/PI3K/AKT axis.

The environmental stability of black phosphorus (BP) is very important for its practical application. Here, we studied the protective effect of 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) passivation layer on the BP against air exposure with photoemission spectroscopy (PES) and density functional theory (DFT) calculations. PES characterization manifests that NTCDA effectively extracts electrons in the BP valence band (VB) and increases the work function (WF) of BP. The PES results reveal a straddling gap (type-I) band alignment at the interface, accompanying with an interface dipole of 0.13 eV pointing from NTCDA to BP and band bending of 0.17 eV in BP. The charge transfer of 0.32 electron per molecule from BP to NTCDA is further confirmed by DFT calculations. Air exposure experimental results demonstrate that NTCDA can improve the environmental stability of BP and slow down the surface oxidation and degradation. Our work deepens the understanding of the passivation mechanism of BP and provides more experimental and theoretical insights for BP’s surface modification and future applications in Two-dimensional (2D) devices.

The hybrid organic–inorganic perovskite (PVK) thin films have attracted amounts of interest in the past decade due to the thickness-depended quantum confinement effects and tunable band gap as well as the demands of device miniaturization. Vacuum deposition is a promising method to realize precise control of film thickness and composition, low-temperature processing, the good compatibility with dry processing and compatible with the modern silicon-based semiconductor industry. Here, we report on the temperature-dependent photoluminescence properties of MAPbI3 ultrathin films with long-term stability and high quality fabricated by the co-evaporation. XPS, AFM and XRD results reveal that an excess MAI vapor environment plays a key role in sample preparation. PL is more sensitive than XPS to detect trace MAPbI3-like materials with strong luminescence properties. Temperature- dependent PL measurements show that the bandgap of MAPbI3 films red-shifted with the temperature decreasing in the range from 298 to 78 K, which is opposite to that of the traditional semiconductors and can be attributed to the interaction between the electron–phonon and the thermal expansion induced band gap renormalization. Gradual phase transition from tetragonal one to orthorhombic one is observed to start between 108 and 118 K, which is lower than the reported sudden phase transition temperature of 150 K for bulk MAPbI3 and suggests the important role of quantum confinement in ultrathin films. Our findings provide a way to fabricate PVK ultrathin films with long-term stability for novel light emitting devices.

Van der Waals (vdW) epitaxial growth provides an efficient strategy to prepare heterostructures with atomically and electronically sharp interfaces. Herein, PbI2 was in situ thermally deposited onto exfoliated thin−layered CrOCl nanoflakes in high vacuum to fabricate vdW PbI2/CrOCl heterostructures. Optical microscopy, atomic force microscopy, X−ray diffraction, and temperature−dependent Raman spectroscopy were used to investigate the structural properties and phonon behaviors of the heterostructures. The morphology of PbI2 films on the CrOCl substrate obviously depended on the substrate temperature, changing from hemispherical granules to 2D nanoflakes with flat top surfaces. In addition, anomalous blueshift of the Ag1 and Au2 modes as the temperature increased in PbI2/CrOCl heterostructure was observed for the first time. Our results provide a novel material platform for the vdW heterostructure and a possible method for optimizing heterostructure growth behaviors.

The interface electronic structure between rubrene and permalloy (Ni80Fe20) has been studied by ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS). We find that the downward energy level bending at the rubrene/NiFe heterostructure is caused by the interaction between rubrene and NiFe at the interface. There is an interface dipole of 0.23 eV, pointing from NiFe to rubrene. Our researches deepen the understanding of the fundamentals and laid a foundation for the design of high-performance rubrene-based organic spintronic devices.

The modification by molybdenum trioxide (MoO3) buffer layer on the electronic structure between Co and black phosphorus (BP) was investigated with ultraviolet photoemission spectroscopy (UPS) and X-ray photoemission spectroscopy (XPS). It was found that the MoO3 buffer layer could effectively prevent the destruction of the outermost BP lattice during the Co deposition, with the symmetry of the lattice remaining maintained. There is a noticeable interfacial charge transfer in addition to the chemical reaction between Co and MoO3. The growth pattern of Co deposited onto the MoO3/BP film is the island growth mode. The observations reveal the significance of a MoO3 buffer layer on the electronic structure between Co and black phosphorus and provide help for the design of high-performance Co/BP-based spintronic devices.

The modification of C60 nano-interlayers on the organic field-effect transistors (OFETs) based on 2,7-diocty[1]benzothieno-[3,2-b]benzothiophene (C8-BTBT)/SiO2 was addressed at both the electronic structure and device level. It is observed that a band bending occurs in C8-BTBT layer with the insertion of C60, which induces a strong hole accumulation at the interface region, facilitating the formation of high concentration conducting channel when the interface is incorporated into OFETs. The strong acceptor C60 may cause charge transfer from the trap states in C8-BTBT, resulting in a field-effect operation with decreased threshold voltage. However, the increasing disorder in C8-BTBT induced by the C60 nano-interlayer may reduce the hole mobility at the C8-BTBT/SiO2 interface region and change the growth model of C8-BTBT. In addition, as confirmed by the transfer characteristic of the OFETs, the thin C60 insertion layer isn’t continuous enough to induce an ambipolar transport behavior despite its high mobility. The competition between the two opposite effects results in compromised performance in such OFETs. The device performance parameters deteriorate generally with increasing the C60 nano-interlayer thickness. So, it is inferred that the C60 interlayer alone cannot improve the performance of the C8-BTBT/SiO2-based OFETs without further optimization. Importantly, the device performance exhibits an abnormal improvement with a 6 nm C60 interlayer, which might be ascribed to a higher energy level shift of C8-BTBT caused by a quasi-continuous C60 film at this thickness.

Ultraviolet-Ozone (UVO) treatment has potentially promoted the long-term stability and the high performance of two-dimensional-material-based devices. However, the detailed evolutions of materials upon UVO treatment are less reported and unclear. Herein, we have systematically investigated the evolutions of morphology and electronic properties of the UVO treated few-layered MoS2. A weak p-doping effect on a 1-hour-UVO-exposed bulk MoS2 is revealed by photoelectron spectroscopy, being attributed to the charge transfer from MoS2 to the newly-formed MoOx. Optical microscopy, atomic force microscopy, Raman and PL mapping measurements reveal an inhomogeneous change of MoS2 morphology after UVO treatment. The oxidation is initiated at intrinsic defect sites and dislocations, and then expands in-plane from dislocations to both sides to form one dimensional standing-wave-like features. The dangling-bond-free surface regions remain smooth, being attributed to the higher energetic barrier for O2 dissociation and chemisorption. A model is proposed to explain the mechanism of inhomogeneous oxidation. The rather different oxidation behavior of MoS2 compared with MoSe2 and MoTe2 can be attributed to the difference in the in-plane chemical bonds. Our findings remind that the device design with UVO oxidation need to take the microstructure changes after treatment into account instead of only taking notice of the doping effect for performance improvement.

The electronic properties of the interface between Al and black phosphorus were studied by photoemission spectroscopy (PES). We observed that the growth pattern of Al deposited onto the BP film is Stranski-Krastanov mode. There is a reaction between Al atoms and P atoms at the interface and forming Al-P compounds, which changes the interface barriers and impedes carrier transfer. It is suggested that an inert buffer layer is necessary to protect BP and lower the carrier barriers to develop Al/BP-based device with high performance.

The cost-effective copper (Cu) nanoparticles and core/shell derived architectures with novel physicochemical properties have received tremendous attention in recent years. Herein, the effect of nanoparticle geometry (including diameter and core/shell ratio) on optical scattering and absorption of Cu@C core/shell nanoparticles has been investigated through a combination of DDA-based simulation and experimental validation. Simulated results have shown that the localized surface plasmon resonance (LSPR) peaks of Cu@C core-shell nanoparticles present slightly blue-shift with the increase of core/shell ratio, the core/shell ratio play the dominant role in the shift of the LSPR peak. Moreover, scattering efficiencies factors are inclined to be increasing faster with particle size and core/shell ratio increase, corresponding to enhanced surface electric field intensity which originated from excessive electron concentration on the interface between Cu core and C shell. Finally, experimental optical absorption performance has been performed with the aim at confirmation of size-sensitive light scattering behaviors of Cu@C core-shell nanoparticles via metal organic chemical vapor deposition technology. Results have found that the light absorption coefficient of up to 99.4% could be achieved for nanoparticles with an average particle diameter of 10 nm, while 98.9% for 23 nm. Further decrease in diameter on the nanometer scale is demonstrated to promote optical absorption to a certain extent, which agrees well with simulated results. All these findings have demonstrated ultra-small Cu@C core-shell nanoparticle to be a promising candidate for efficient optical absorption, and are beneficial for design and development of Cu@C core-shell nanoparticles enabled optical-based devices.

R2R printing: organic devices closer to commercialization Roll-to-roll printing is getting close to the large-scale fabrication of reliable and stable state-of-the-art organic optoelectronic devices. A collaborative team led by Junliang Yang from Central South University, China presents roll-to-roll (R2R) micro-gravure printing method to fabricate high performance and highly stable organic photodetectors on PET or paper substrates in large scale. They find that the bulk heterojunction structure of PBDTT-ffQx/PCBM, a well-known system for organic solar cell, also works as a high-performance photodetector, showing broadband responsivity, high detectivity, and a high photocurrent to dark current ratio. The performance retains over 80% after 10,000 bending cycles or ambient exposure for 50 days. The printed photodetectors have demonstrated good homogeneity, reliability, stability, and reproducibility, showing the promises for large-scale production of printed organic optoelectronic devices.

The surface composition and morphology of FA0.85MA0.15Pb(I0.85Br0.15)3 films fabricated by the spin-coating method with different concentrations of NH2-POSS were investigated with atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), angle-resolved X-ray photoelectron spectroscopy (AR-XPS), and Fourier transform infrared spectroscopy (FTIR). It was found that the surface composition of the FA0.85MA0.15Pb(I0.85Br0.15)3 films was changed regularly through the interaction between NH2-POSS and the perovskite film. The corresponding surface morphological changes were also observed. When the concentration of NH2-POSS exceeded 10 mg/mL, a lot of cracks on the surface of the perovskite film were observed and the surface morphology was damaged. The surface composition and its distribution can be adjusted by changing the concentration of NH2-POSS and the proper concentration of NH2-POSS can substantially improve the quality of perovskite film.

A novel optimal scheduling method considering demand response is proposed for power systems incorporating with large scale wind power. The proposed method can jointly dispatch the energy resources and demand side resources to mitigate the fluctuation of load and wind power output. It is noticed in practical operation that, without customer's satisfaction being considered, customers might reject the too frequent or violent demand response all together. In this case, two indices that measure the customer satisfaction are then introduced as constraints to reduce the impact to end-users and avoid extreme demand adjustment. To make the model solvable, a proximate decoupling technique is used to dispose the concave constraint introduced by the customer satisfaction constraints. Results from the case studies show that the proposed model can significantly reduce the operation cost of power system while the demand response meets customer satisfaction. Especially, the total start-up costs of conventional thermal units decreases dramatically due to less startup times. Moreover, compared to the consumption way satisfaction constraint, the payment satisfaction constraint has a heavier influence on the cost.

High-voltage direct current (HVDC) grids are emerging, and their reliability has been an increasing concern for the utilities. HVDC grids are different from typical two-terminal HVDC transmission systems due to the loops in their topology, which makes it difficult to evaluate the reliability by conventional analytical methods. This paper proposes an innovative hybrid method to evaluate the reliability of meshed HVDC grids. First, steady-state models and reliability models are established for the components in HVDC grids, especially for converters and power flow controllers. In the models, virtual buses are introduced to represent the external AC connections to the HVDC grid. Then a hybrid reliability evaluation method is proposed based on an analytical approach and Monte Carlo simulation. One innovation of the paper is the application of an analytical analysis method to accelerate state evaluation in Monte Carlo simulation by skipping unnecessary optimization. The proposed models and methods are verified on two HVDC grids. Test results show that HVDC grids under most failure states (approximately 70%) tend to shed no load except on buses connected to faulted converters, and the application of the analytical method could promote evaluation efficiency significantly.

As the scale of wind power bases rises, it becomes significant in power system planning and operation to provide detailed correlation characteristic of wind speed in different geographical hierarchies, that is among wind turbines, within a wind farm and its regional wind turbines, and among different wind farms. A new approach to analyze the correlation characteristics of wind speed in different geographical hierarchies is proposed in this paper. In the proposed approach, either linear or nonlinear correlation of wind speed in each geographical hierarchy is firstly identified. Then joint sectionalized wind speed probability distribution is modeled for linear correlation analysis while a Copula function is adopted in nonlinear correlation analysis. By this approach, temporal-geographical correlations of wind speed in different geographical hierarchies are properly revealed. Results of case studies based on Jiuquan Wind Power Base in China are analyzed in each geographical hierarchy, which illustrates the feasibility of the proposed approach.

Two dimensional atomic crystals, like grapheme (G) and molybdenum disulfide (MoS2), exhibit great interest in electronic and optoelectronic applications. The excellent physical properties, such as transparency, semiconductivity, and flexibility, make them compatible with current organic electronics. Here, we review recent progress in the understanding of the interfaces of van der Waals (vdW) heterostructures between small organic molecules (pentacene, copper phthalocyanine (CuPc), perylene-3,4,9,10-tetracarboxylic dianhydride (PTCDA), and dioctylbenzothienobenzothiophene (C8-BTBT)) and layered substrates (G, MoS2 and hexagonal boron nitride (h-BN)). The influences of the underlying layered substrates on the molecular arrangement, electronic and vibrational properties will be addressed.

Interfacial interactions, including interfacial charge transfer and strain, play important roles in the applications of 2D layered materials. Recently, MoO2 have been widely used as precursors or substrates for growth of high-quality MoS2. Herein, photoluminescence (PL) and Raman spectroscopy are used to investigate the dependence of epitaxial monolayer MoS2 PL properties on MoO2 nanoflakes in different thicknesses on c-sapphire. On all MoO2 nanoflakes, the trion exciton of MoS2 disappears due to the interfacial charge transfer from MoS2 to MoO2. The neutral exciton of MoS2 exhibits a -60meV redshift on thick MoO2 nanoflakes compared to those either on c-sapphire or on thin MoO2 nanoflakes, which is attributed to the relaxation of c-sapphire-induced compressive strain in MoO2 over a critical thickness. Temperature-dependent PL measurements reveal a stronger electron-phonon interaction in MoS2 on MoO2 than on c-sapphire. The findings provide an easy way to tune the properties of MoS2 via tuning the thickness of MoO2 buffer layer on c-sapphire. [ABSTRACT FROM AUTHOR]