In Situ Self-Assembled 1D/3D Mixed-Dimensional Perovskite Heterostructures for Efficient White Light Emission.

Mixed-dimensional perovskite (MDP) heterostructures are promising optoelectronic semiconductors. Yet, the current preparation methods involve complex experimental procedures and material compatibility constraints, limiting their widespread applications. Here, we present a one-step room temperature solution-based approach to synthesize a range of 1D C4N2H14PbBr4 and 3D APbBr3 (A = Cs+, MA+, FA+) self-assembled MDP heterostructures exhibiting high-efficiency white light-emitting properties. The ultra-broadband emission results from the synergy between the self-captured blue broadband emission from 1D perovskites and the green emission of 3D perovskites, covering the entire visible-light spectrum with a full width at half-maximum exceeding 170 nm and a remarkable photoluminescence quantum yield of 26%. This work establishes a novel prototype for the preparation of highly luminescent MDP heterostructures, offering insights for future research and industrialization in the realm of white light LEDs.

Light-induced reversal of ion segregation in mixed-halide perovskites.

Bandgap instability due to light-induced phase segregation in mixed-halide perovskites presents a major challenge for their future commercial use. Here we demonstrate that photoinduced halide-ion segregation can be completely reversed at sufficiently high illumination intensities, enabling control of the optical bandgap of a mixed-halide perovskite single crystal by optimizing the input photogenerated carrier density. We develop a polaron-based two-dimensional lattice model that rationalizes the experimentally observed phenomena by assuming that the driving force for photoinduced halide segregation is dependent on carrier-induced strain gradients that vanish at high carrier densities. Using illumination sources with different excitation intensities, we demonstrate write-read-erase experiments showing that it is possible to store information in the form of latent images over several minutes. The ability to control the local halide-ion composition with light intensity opens opportunities for the use of mixed-halide perovskites in concentrator and tandem solar cells, as well as in high-power light-emissive devices and optical memory applications.

Visualizing Phase Segregation in Mixed-Halide Perovskite Single Crystals.

Mixed organolead halide perovskites (MOHPs), CH3 NH3 Pb(Brx I1-x )3 , have been shown to undergo phase segregation into iodide-rich domains under illumination, which presents a major challenge to their development for photovoltaic and light-emitting devices. Recent work suggested that phase-segregated domains are localized at crystal boundaries, driving investigations into the role of edge structure and the growth of larger crystals with reduced surface area. Herein, a method for growing large (30×30×1 µm3 ) monocrystalline MAPb(Brx I1-x )3 single crystals is presented. The direct visualization of the growth of nanocluster-like I-rich domains throughout the entire crystal revealed that grain boundaries are not required for this transformation. Narrowband fluorescence imaging and time-resolved spectroscopy provided new insight into the nature of the phase-segregated domains and the collective impact on the optoelectronic properties.

Controlled Growth of Monocrystalline Organo-Lead Halide Perovskite and Its Application in Photonic Devices.

Organo-lead halide perovskites (OHPs) have recently emerged as a new class of exceptional optoelectronic materials, which may find use in many applications, including solar cells, light emitting diodes, and photodetectors. More complex applications, such as lasers and electro-optic modulators, require the use of monocrystalline perovskite materials to reach their ultimate performance levels. Conventional methods for forming single crystals of OHPs like methylammonium lead bromide (MAPbBr3 ) afford limited control over the product morphology, rendering the assembly of defined microcavity nanostructures difficult. We overcame this by synthesizing for the first time (MA)[PbBr3 ]⋅DMF (1), and demonstrating its facile transformation into monocrystalline MAPbBr3 microplatelets. The MAPbBr3 microplatelets were tailored into waveguide based photonic devices, of which an ultra-low propagation loss of 0.04 dB µm-1 for a propagation distance of 100 µm was demonstrated. An efficient active electro-optical modulator (AEOM) consisting of a MAPbBr3 non-linear arc waveguide was demonstrated, exhibiting a 98.4 % PL intensity modulation with an external voltage of 45 V. This novel synthetic approach, as well as the demonstration of effective waveguiding, will pave the way for developing a wide range of photonic devices based on organo-lead halide perovskites.

One-nanometer-precision control of Al(2)O(3) nanoshells through a solution-based synthesis route.

Forming uniform metal oxide nanocoatings is a well-known challenge in the construction of core-shell type nanomaterials. Herein, by using buffer solution as a specific reaction medium, we demonstrate the possibility to grow thin nanoshells of metal oxides, typically Al2 O3 , on different kinds of core materials, forming a uniform surface-coating layer with thicknesses achieving one nanometer precision. The application of this methodology for the surface modification of LiCoO2 shows that a thin nanoshell of Al2 O3 can be readily tuned on the surface for an optimized battery performance.

Precursor Engineering of Lead Acetate-Based Precursors for High-Open-Circuit Voltage Wide-Bandgap Perovskite Solar Cells.

Wide-bandgap (WBG) perovskites have great potential for inclusion in efficient tandem solar cells, but large open-circuit voltage losses have limited device performance to date. Here, we show that a high-quality WBG perovskite, FA0.83Cs0.17Pb(I0.8Br0.2)3, with enlarged grain sizes and improved crystallinity can be achieved by incorporating lead chloride (PbCl2) into a lead acetate (PbAc2)-based precursor. The improved film quality resulted in the suppression of nonradiative recombination and a reduction in defect density. Efficient WBG perovskite solar cells (1.66 eV) with an efficiency of 19.3% and a high Voc of 1.22 V were fabricated using a facile one-step spin-coating method without the need for an antisolvent. Notably, the unencapsulated devices retained 90% of their initial power conversion efficiency after storage in a dry box (10% humidity) for 800 h.

What inhibits regional inclusive green growth? Empirical evidence from China.

The diversity of locations, environment, and resource elements among different regions leads to the regional imbalance of inclusive green growth (IGG), especially in those developing countries like China. A core issue for achieving the coordination of regional IGG is to identify what influence factors with what extent to inhibit IGG levels of different regions. In this paper, a comprehensive IGG indicator system is designed based on the IGG connotation from four dimensions of economic development, social opportunity equity, green production and consumption, and ecological environment protection. An improved TODIM method is proposed to measure the regional IGG level and further reveal the inhibition effects of various influence factors on regional IGG. The results exemplified by China's 30 provinces during 2008-2018 show that China's eastern provinces possess more superior IGG levels, while the catch-up effect of IGG in central and western provinces is significant. The lower economic output, larger income gap, and weaker green production and consumption restrict the IGG of most western provinces. The higher economic and population agglomerations in eastern and central provinces challenge the ecological resource endowment and environment governance, which inhibits their IGG development. The inhibition effects of social opportunity equity involving employment, education, medical treatment, social security, and infrastructure on IGG levels do not reflect obvious regional agglomeration.

FunSwin: A deep learning method to analysis diabetic retinopathy grade and macular edema risk based on fundus images.

Diabetic retinopathy (DR) and age-related macular degeneration (AMD) are forms of degenerative retinal disorders that may result in vision impairment or even permanent blindness. Early detection of these conditions is essential to maintaining a patient's quality of life. The fundus photography technique is non-invasive, safe, and rapid way of assessing the function of the retina. It is widely used as a diagnostic tool for patients who suffer from fundus-related diseases. Using fundus images to analyze these two diseases is a challenging exercise, since there are rarely obvious features in the images during the incipient stages of the disease. In order to deal with these issues, we have proposed a deep learning method called FunSwin. The Swin Transformer constitutes the main framework for this method. Additionally, due to the characteristics of medical images, such as their small number and relatively fixed structure, transfer learning strategy that are able to increase the low-level characteristics of the model as well as data enhancement strategy to balance the data are integrated. Experiments have demonstrated that the proposed method outperforms other state-of-the-art approaches in both binary and multiclass classification tasks on the benchmark dataset.

Intensity Modulated Photocurrent Microspectrosopy for Next Generation Photovoltaics.

In this report, a large-area laser beam induced current microscope that has been adapted to perform intensity modulated photocurrent spectroscopy (IMPS) in an imaging mode is described. Microscopy-based IMPS method provides a spatial resolution of the frequency domain response of the solar cell, allowing correlation of the optoelectronic response with a particular interface, bulk material, specific transport layer, or transport parameter. The system is applied to study degradation effects in back-contact perovskite cells where it is found to readily differentiate areas based on their markedly different frequency response. Using the diffusion-recombination model, the IMPS response is modeled for a sandwich structure and extended for the special case of lateral diffusion in a back-contact cell. In the low-frequency limit, the model is used to calculate spatial maps of the carrier ambipolar diffusion length. The observed frequency response of IMPS images is then discussed.

Optimal path for overcoming barriers in developing China's wind energy industry.

Developing the wind energy industry (WEI) has been a long-term strategy in China for responding to the energy crisis and greenhouse gas emissions. However, China's WEI faces various barriers despite its favorable prospects. This paper aims to propose a path analysis approach for exploring the best methods and timing for overcoming diverse barriers in developing WEI systematically, especially in terms of revealing in which phases these barriers should take priority. A multidimensional barrier set categorized by institutional, economic and financial, social, technical, and market factors is identified via the integration of a literature review and empirical interviews. A path analysis approach based on the grey group DEMATEL-NK model is constructed, where the causalities and intensities among barriers are extracted to design a path simulation algorithm with heuristics. The optimal path for overcoming barriers in developing the WEI is generated through a simulation of the search and optimization process used to climb to the fitness landscape peak. The results show that the different barriers to completing the legal and regulatory framework should be prioritized to reach adequate financial incentives and coordination among stakeholders, and that an efficient talent cultivation system should be developed and industry-academic cooperation should be strengthened to increase technical and R&D capabilities in the short term. The optimal path presents a strategic instrument for managers to use to better develop sustainable and clean wind energy systems from the novel insights of prioritizing to overcome barriers.

Barriers to implementing the strictest environmental protection institution: a multi-stakeholder perspective from China.

Increasingly severe environmental issues, especially those in developing countries such as China, drive the evolution of the environmental protection institution (EPI) to its strictest levels. However, the implementation of the strictest EPI still confronts various challenges and barriers, and the multi-stakeholder features of EPI determine these barriers are not independent of one another but rather present complex interactive relationships. This paper identifies the barriers to implementing China's EPI from four aspects of environmental legal, economic, regulatory, and public participation institutions. A variable precision rough DEMATEL approach is proposed to visualize the causal relationships and intensities among barriers from the similarities and differences in perspectives of stakeholders from the government, company, and public levels. The obtained causal interactive mechanism among barriers highlights the need to prioritize the improvement of environmental policy assessment, and the concrete measures in policies or plans should be integrated into legislation to ensure they are mutually supportive early. The non-substantive contributions achieved by China's public participation in environmental protection reveal prejudices that the public is often regarded as a supporter or spectator by both government and company groups, which makes the transparent environmental information disclosure, transfer and feedback into an effective mediation among stakeholders. Comprehensive coordination and feedback mechanisms including source prevention, process control, and severe punishment for consequences while enhancing linkages among stakeholders are put forward to overcome barriers and help implement the strictest EPI.

Solution-Processed Faraday Rotators Using Single Crystal Lead Halide Perovskites.

Lead halide perovskites (LHPs) have become a promising alternative for a wide range of optoelectronic devices, thanks to their solution-processability and impressive optical and electrical properties. More recently, LHPs have been investigated in magneto-optic studies and have exhibited spin-polarized emission, photoinduced magnetization, and long spin lifetimes. Here, the viability of methylammonium lead bromide (MAPbBr3) single crystals as solution-processed Faraday rotators is demonstrated. Compared to terbium gallium garnet, the industry standard in the visible, it is found that MAPbBr3 exhibits Verdet constants (i.e., strength of Faraday effect) of similar or greater magnitude (up to 2.5x higher), with lower temperature dependence. Due to its low trap absorption, it is calculated that an optical isolator made from MAPbBr3, with appropriate antireflection coatings, should reach ≈95% transmission and achieve 40 dB isolation for incoming powers of over 2 W. It is also shown that the Verdet constant of MAPbBr3 can be calculated accurately from its dispersion in refractive index, allowing the possibility to predict similar effects in other perovskite materials.

Driving patterns of industrial green transformation: A multiple regions case learning from China.

A core issue for achieving successful industrial green transformation is to identify what driving factors under which kinds of synergistic combination methods with how strong driving strengths will lead to the superior driving patterns of green transformation. This paper focuses on the novel perspective of learning and mining historical cases of industrial green transformation in China's multiple regions, and a three-phase case learning theoretical framework of learning-validation-generalization based on rough set theory is constructed to identify the driving patterns from regional level. The extracted decision rules set reveals the potential synergistic relationships of different heterogeneous driving factors on industrial green transformation from the multiple paths of structure transformation and efficiency transformation. The results show that the key driving factors of structure transformation and efficiency transformation presents certain differences and obvious spatial effect. The higher resource allocation efficiency, stronger investment scale and lower resource endowment dominate the industrial green transformation's core features, which distinguish the superior driving patterns from the inferior, in China's eastern, central and western regions respectively. The driving patterns provide policy-makers extra insights to guide different regions to adjust and optimize their green transformation through developing the regional advantages and bypassing the insufficiencies in historical cases.

Flexible photodetectors based on reticulated SWNT/perovskite quantum dot heterostructures with ultrahigh durability.

Recently, single-walled carbon nanotube (SWNT) films have been regarded as a promising channel material for flexible photodetectors due to their high intrinsic carrier mobility, conductivity, and mechanical flexibility. However, the application of SWNTs in photonic devices is limited due to their weak light absorption and the absence of a gain mechanism. Here, we demonstrate a high-performance flexible photodetector that consists of a reticulated SWNT film covered with a thin film of CsPbI3 perovskite colloidal quantum dots. The unique hierarchical reticulated structure of the SWNTs provides such films with extremely high tensile strength and great extensibility, which can ensure the appropriate toughness for achieving flexible photodetectors. Meanwhile, the perovskite quantum dots enhance light absorption, thereby sensitizing the creation of free electrical carriers within the SWNTs. This hybrid photodetector exhibits an extended photonic response and gain compared with the original pure SWNT devices. In addition, the device exhibits good robustness against repetitive bending and stretching, suggesting its applicability as a large-area wearable flexible photodetector.

The optical properties of Cs4PbBr6-CsPbBr3 perovskite composites.

Although the optoelectronic applications of metal halide perovskites have been intensively investigated in recent years, the fundamental carrier dynamics of zero-dimensional (0D) Cs4PbBr6 perovskites has been relatively underexplored; in particular, the nature of the green fluorescence is highly debated. Nevertheless, the unique photophysical properties are of immense interest for a variety of potential applications. In this work, the green emission of the CsPbBr3-Cs4PbBr6 perovskite composites is studied using temperature dependent photoluminescence (PL). The PL spectra at different temperatures simultaneously contain two sub-peaks (520 nm and 550 nm), which are ascribed to the emissions of the band-edge and the defect trapped exciton of CsPbBr3. This finding will help to understand the controversial photoluminescence currently observed in different 0D Cs4PbBr6 perovskites.

A Decision-Making Method with Grey Multi-Source Heterogeneous Data and Its Application in Green Supplier Selection.

In view of the multi-attribute decision-making problem that the attribute values are grey multi-source heterogeneous data, a decision-making method based on kernel and greyness degree is proposed. The definitions of kernel and greyness degree of an extended grey number in a grey multi-source heterogeneous data sequence are given. On this basis, we construct the kernel vector and greyness degree vector of the sequence to whiten the multi-source heterogeneous information, then a grey relational bi-directional projection ranking method is presented. Considering the multi-attribute multi-level decision structure and the causalities between attributes in decision-making problem, the HG-DEMATEL method is proposed to determine the hierarchical attribute weights. A green supplier selection example is provided to demonstrate the rationality and validity of the proposed method.

Core-shell structured TiO2@polydopamine for highly active visible-light photocatalysis.

This communication reports that the TiO2@polydopamine nanocomposite with a core-shell structure could be a highly active photocatalyst working under visible light. A very thin layer of polydopamine at around 1 nm was found to be critical for the degradation of Rhodamine B.

In Situ Encapsulation of Ultrasmall CuO Quantum Dots with Controlled Band-Gap and Reversible Thermochromism.

Silica encapsulated ultrasmall CuO quantum dots (QDs; CuO@SiO2) were synthesized by reverse microemulsion. The CuO QDs with sizes ranging from 2.0 to 1.0 nm with corresponding band gaps of 1.4 to 2.6 eV were prepared simply by varying the concentration of the Cu(2+) precursor. The samples were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and UV-vis spectroscopy. The CuO@SiO2 composite displayed reversible thermochromism which resulted from the strong electron-phonon coupling of ultrasmall CuO in the confined space of SiO2 and the enhanced band-gap shift in the visible light region depending on temperature. Besides, the as synthesized CuO@SiO2 was found to be highly stable for reversible thermochromism due to the micropore structure of silica matrix and local confinement of the QDs.