Room-Temperature Continuous-Wave Microcavity Lasers from Solution-Processed Smooth Quasi-2D Perovskite Films with Low Thresholds.

Continuous-wave (CW) lasing in quasi-two-dimensional (2D) perovskite-based distributed feedback cavities has been achieved at room temperature; however, CW microcavity lasers comprising distributed Bragg reflectors (DBRs) have rarely been prepared using solution-processed quasi-2D perovskite films because the roughness of perovskite films significantly increases intersurface scattering loss in the microcavity. Herein, high-quality spin-coated quasi-2D perovskite gain films were prepared using an antisolvent to reduce roughness. The highly reflective top DBR mirrors were deposited via room-temperature e-beam evaporation to protect the perovskite gain layer. Lasing emission of the prepared quasi-2D perovskite microcavity lasers under CW optical pumping was clearly observed at room temperature, featuring a low threshold of ∼1.4 W cm-2 and beam divergence of ∼3.5°. It was concluded that these lasers originated from weakly coupled excitons. These results elucidate the importance of controlling the roughness of quasi-2D films to achieve CW lasing, thus facilitating the design of electrically pumped perovskite microcavity lasers.

Morphology and Luminescence Regulation for CsPbBr3 Perovskite Light-Emitting Diodes by Controlling Growth of Low-Dimensional Phases.

At present, the high defect density and strong nonradiative recombination rate of all-inorganic cesium lead bromide (CsPbBr3) perovskite light-emitting diodes (PeLEDs) seriously inhibit the improvement of their quantum efficiency. In this paper, the addition of a short-chain additive, diethylammonium bromide (DEABr), aims to control the generation of a quasi-2D large n-phase to optimize the surface morphology and construct two-dimensional/three-dimensional (2D/3D) heterojunction perovskite structures to enhance the EL efficiency of PeLEDs. Through Kelvin probe force microscopy (KPFM) characterization, we confirmed that the 2D phase grains with a low potential are locally formed on the surface of the perovskite film under the action of DEABr. The existence of the 2D phase effectively improved the surface morphology and suppressed surface defects. In addition, the in situ constructed 2D/3D heterojunction perovskite structure further increases the exciton radiative recombination rate and significantly improves the electroluminescent performance. By optimizing its doping concentration, the optimal all-inorganic PeLED displays a current efficiency (CE) of 30.3 cd A-1, an external quantum efficiency (EQE) of 9.6%, and a maximum brightness of 32,500 cd m-2. According to our results, the formation of 2D structures on the surface of the CsPbBr3 film can improve surface morphology issues and optoelectronic properties of the film.

Efficient Inorganic Perovskite Light-Emitting Diodes by Inducing Grain Arrangement via a Multifunctional Interface.

Accumulating evidence shows that metal halide perovskite light-emitting diodes (PeLEDs) are well-described to show broad application prospects in lighting and display due to the wide color gamut and high color purity. However, it is still a great challenge to prepare high-quality all-inorganic PeLEDs by a solution method. For example, it is difficult to obtain all-inorganic perovskite films with good crystallinity and high grain orientation because of too fast and uncontrollable crystallization of all-inorganic perovskite films. Here, we demonstrated a multifunctional interface of formamide (FA)-doped PEDOT:PSS, which improved the crystallinity of all-inorganic perovskite films by inducing grain arrangement. As a result, a highly crystalline, ordered, and defect-passivated CsPbBr3 film was obtained by the multiple roles of FA, and the CsPbBr3-based PeLED treated with FA achieved both high brightness and high efficiency: the peak external quantum efficiency (EQE) reaches 9.61%, and the maximum brightness is 185,000 cd/m2. In addition, Tween 80, used as a passivator of perovskite films, reduced the defect states and suppressed ion migration. Under the synergistic effect of FA interface treatment and Tween 80 passivation treatment, efficient CsPbBr3-based PeLEDs were obtained with an EQE of 15.02% and an operation lifetime of 182.5 min at an initial brightness of 1000 cd/m2, which is among the best reported lifetimes under high brightness. Our study provides a simple and effective strategy for the realization of all-inorganic PeLEDs with high efficiency, high brightness, and ultralong operation lifetime.

A Novel Factor Graph and Cubature Kalman Filter Integrated Algorithm for Single-Transponder-Aided Cooperative Localization.

Cooperative localization (CL) of underwater multi-AUVs is vital for numerous underwater operations. Single-transponder-aided cooperative localization (STCL) is regarded as a promising scheme for multi-AUVs CL, benefiting from the fact that an accurate reference is adopted. To improve the positioning accuracy and robustness of STCL, a novel Factor Graph and Cubature Kalman Filter (FGCKF)-integrated algorithm is proposed in this paper. In the proposed FGCKF, historical information can be efficiently used in measurement updating to overcome uncertain observation environments, which greatly helps to improve the performance of filtering progress. Furthermore, Adaptive CKF, sum product, and Maximum Correntropy Criterion (MCC) methods are designed to deal with outliers of acoustic transmission delay, sound velocity, and motion velocity, respectively. Simulations and experiments are conducted, and it is verified that the proposed FGCKF algorithm can improve positioning accuracy and robustness greatly than traditional filtering methods.

Joint Resource Allocation of Spectrum Sensing and Energy Harvesting in an Energy-Harvesting-Based Cognitive Sensor Network.

The cognitive sensor (CS) can transmit data to the control center in the same spectrum that is licensed to the primary user (PU) when the absence of the PU is detected by spectrum sensing. However, the battery energy of the CS is limited due to its small size, deployment in atrocious environments and long-term working. In this paper, an energy-harvesting-based CS is described, which senses the PU together with collecting the radio frequency energy to supply data transmission. In order to improve the transmission performance of the CS, we have proposed the joint resource allocation of spectrum sensing and energy harvesting in the cases of a single energy-harvesting-based CS and an energy-harvesting-based cognitive sensor network (CSN), respectively. Based on the proposed frame structure, we have formulated the resource allocation as a class of joint optimization problems, which seek to maximize the transmission rate of the CS by jointly optimizing sensing time, harvesting time and the numbers of sensing nodes and harvesting nodes. Using the half searching method and the alternating direction optimization, we have achieved the sub-optimal solution by converting the joint optimization problem into several convex sub-optimization problems. The simulation results have indicated the predominance of the proposed energy-harvesting-based CS and CSN models.