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It was proposed that ionic liquids (IL) used as the gated dielectric in EDLT can form a strong electric fi eld at the interface between IL and oxides to electrostatically manipulate the high carrier density in a range of ≈10 14 -10 15 cm −2 , leading to the change of the electronic phase of transitional metal oxides, while it is not achievable via fi eld-effect transistor gated with conventional dielectric. [4][5][6][7][8][9][10][11][12][13][14][15][16] However, some recent reports argued that the mechanism of electronic phase change is the creation of oxygen vacancies caused by the electric fi eld in oxides, [17][18][19][20] instead of electrostatic carrier doping. On the other hand, some other results claimed that the change of the electronic phase in correlated oxides is the result of chemical doping via an electrochemical reaction. [21][22][23][24] Despite these great efforts that have been made, the underlying mechanism of IL gating driving MIT has been a matter of debate so far. Therefore, it is of vital importance to reveal the origin of the electrical control of MIT in transitional metal oxides using IL as gate mediums.The perovskite manganite materials are of signifi cant interest for those who wish to control and understand MIT in correlated oxides, as well as an excellent platform for exploring how the oxygen vacancies occur and what role they play in the electronic phase transition by electrolyte gating, because of the high correlation with the valence state of manganese determined by the oxygen stoichiometry. [ 2,25 ] In this work, we focus on a typical hole-doped perovskite oxide material, La 0.8 Sr 0.2 MnO 3 (LSMO), featured with colossal magnetoresistance and phase separation. [ 25 ] First, we will present the manipulation of the electronic phase transition by using IL gating, and the realization of a resistance increase of more than four orders of magnitude in the LSMO fi lms. Then it will be shown that the oxygen vacancies are responsible for MIT of LSMO fi lms. Finally from a series of comparative experiments presented in this work, we conclude that these oxygen vacancies are originated by the electrochemical reaction at the interface gated by IL electrolytes, and the amount of the trace water contained in the IL plays an indispensable role in the generation of oxygen vacancies in LSMO fi lms.The thin fi lms of LSMO were grown on single crystal (001) LaAlO 3 (LAO) substrates by pulsed laser deposition. The crosssectional high-angle annular dark-fi eld (HAADF) scanning transmission electron microscopy (STEM) image exhibits the LSMO/LAO sharp interface, indicating a high quality of the epitaxial heterostructure ( Figure S1, Supporting Information). It was patterned into a Hall-bar structure with coplanar In correlated transitional metal oxides, the coupling of charge, spin, orbital, and lattice degree of freedoms gives rise to the rich physics, including metal-insulator transition (MIT) [ 1 ] and interface related multifunctional properties. [ 2 ] The electric fi eld control of these intriguing p...

rich chemical and structural diversity of these solution-processed MHPs enables a series of fascinating luminescent materials for perovskite light-emitting diodes (PeLEDs). [2] Benefit from the perovskite film morphology controlling, composition adjusting, dimensionality tuning, optical coupling, and interface engineering, the external quantum efficiencies (EQEs) of PeLEDs have rapidly increased from below 1% to over 20% in 5 years. [3] With the increasing quantum yield of perovskite emission layer, the reported EQE values of PeLEDs are even comparable to the best performing quantum dot light-emitting diodes. [4] However, the excitons quenching at the interfacial between emission layer and charge transport layers still limit the further increase of luminescence efficiency. Suppressing the energy loss at the interfaces becomes the key to the realization of the near-unity radiative recombination for PeLED devices.In a conventional PeLED device structure, the conducting polymer poly(3,4ethylenedioxythiophene):poly styrene sulfonate (PEDOT:PSS) is the most commonly used a hole injection layer (HIL). However, the exciton quenching effect at interface between emission and PEDOT:PSS layers seriously restricts the device performance including the EQE and long-term device stability. The modification of PEDOT:PSS has been extensively studied to alleviate For metal halide perovskite (MHP)-based light-emitting diodes (PeLEDs), effective radiative recombination of the injected holes and electrons within the MHP layer and minimized injection energy barriers at the interfaces between MHP emission layer and charge injection layers are prerequisites for high-performance and stable PeLEDs. Herein, for the first time, novel p-type carbon quantum dots (CQDs) are introduced as a hole injection layer in PeLEDs to replace acidic poly(3,4-ethylenedioxythiophene):poly styrene sulfonate (PEDOT:PSS) layer. The CQDs demonstrate high hole transport mobility and desirable hole injection energy level. Moreover, the carboxyl, amine, and hydroxyl groups on CQDs not only offer a hydrophilic surface for high-quality perovskite layer growth, but also passivate the perovskite surface defects to suppress the interfacial exciton quenching. Based on the multifunctional p-type CQDs, high-performance green CsPbBr 3 PeLEDs with a low turn-on voltage of only 2.8 V, maximum luminance of 25 770 cd m −2 , and maximum external quantum efficiency (EQE) of 13.8% are achieved. The PeLEDs also show good operational stability and long-term environmental stability. The first application of CQDs as a hole injection layer in PeLEDs breaks through the traditional cognition of carbon materials and opens up new pathways for the developments of carbon nanomaterials in optoelectronic devices.

Reduced graphene oxides with varying degrees of reduction have been produced by hydrazine reduction of graphene oxide. The linear and nonlinear optical properties of both graphene oxide as well as the reduced graphene oxides have been measured by single beam Z-scan measurement in the picosecond region. The results reveal both saturable absorption and two-photon absorption, strongly dependent on the intensity of the pump pulse: saturable absorption occurs at lower pump pulse intensity (~1.5 GW/cm 2 saturation intensity) whereas two-photon absorption dominates at higher intensities (≥5.7 GW/cm 2 ). Intriguingly, we find that the two-photon absorption coefficient (from 1.5 cm/GW to 4.5cm/GW) and the saturation intensity (from 1 GW/cm 2 to 2 GW/cm 2 ) vary with chemical reduction, which is ascribed to the varying concentrations of sp 2 domains and sp 2 clusters in the reduced graphene oxides. Our results not only provide an insight into the evolution of the nonlinear optical coefficient in reduced graphene oxide, but also suggest that chemical engineering techniques may usefully be applied to tune the nonlinear optical properties of various nanomaterials, including atomically thick graphene sheets.

In comparison with the ECMWF data, some obviously positive differences exist at high southern latitudes in January and at high northern latitudes in July.

Lead‐free perovskite emitters, particularly 2D tin (Sn) halide perovskites, have attracted considerable academic attention in recent years. However, the problems of Sn oxidation and rapid crystallization lead to an inferior perovskite morphology with high trap states, thus limiting the luminous efficiency of Sn halide perovskite light‐emitting diodes (PeLEDs). In this study, the authors establish an approach by introducing an organic additive, 2–imidodicarbonic diamide (biuret), to address the issues of Sn oxidation and fast crystallization. The unique symmetrical carbonyl groups in the biuret robustly interact with the Sn‐I framework, providing a strong Sn‐anchoring effect. Consequently, it also suppresses the easy oxidation of Sn2+, regulating the crystallization process simultaneously. Density functional theory (DFT) calculations also confirmed the robust interaction between the biuret and the 2D Sn halide perovskite. Furthermore, the authors demonstrate efficient PeLEDs with saturated red emission at 637 nm, a maximum luminance (Lmax) of 418 cd m−2, a maximum external quantum efficiency (EQEmax) of 1.37%, and a half‐life (T50) of 288 s. This work provides insights on the microcosmic chemical interaction between organics and 2D Sn halide perovskites, advancing the development of efficient lead‐free PeLEDs.

Spatial heterodyne Raman spectroscopy (SHRS) is a new type of effective method for the analysis of structure and composition of liquid and solid targets with the characteristics of no moving parts, high spectral resolution, high optical throughput and large field of view. The technique is very suitable for detecting the targets from long distances or under the conditions with ambient light, which is essential for the exploration of planetary surface. In order to have a better understanding of the ability of SHRS for the detection of liquid and solid targets, a breadboard was designed, built and calibrated. Signal to noise was estimated at different integration time or laser power for carbon tetrachloride. Pure materials or materials contained in bottles were both tested. The mixture of organic liquids or inorganic solids were tested. In order to test the detection ability for natural targets, some composition-unknown rocks and pebbles were tested. The results have shown that SHRS can meet the requirements for the detection of weak Raman signal scattered from artificial or natural targets. Standoff detection of sulfur from 5-m or 10-m distance without using any telescope or collimation optics was also tried to test the high optical throughput of SHRS. The potential feasibility of standoff detection has been proved.