This paper considers the state estimation problem of bilinear systems in the presence of disturbances. The standard Kalman filter is recognized as the best state estimator for linear systems, but it is not applicable for bilinear systems. It is well known that the extended Kalman filter (EKF) is proposed based on the Taylor expansion to linearize the nonlinear model. In this paper, we show that the EKF method is not suitable for bilinear systems because the linearization method for bilinear systems cannot describe the behavior of the considered system. Therefore, this paper proposes a state filtering method for the single-input–single-output bilinear systems by minimizing the covariance matrix of the state estimation errors. Moreover, the state estimation algorithm is extended to multiple-input–multiple-output bilinear systems. The performance analysis indicates that the state estimates can track the true states. Finally, the numerical examples illustrate the specific performance of the proposed method.

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State estimation for bilinear systems through minimizing the covariance matrix of the state estimation errors

This paper considers the parameter estimation problems of two-input single-output Hammerstein finite impulse response systems. A hierarchical least squares algorithm is proposed for improving the computational efficiency through combining the hierarchical identification principle and the identification model decomposition, and a multi-innovation least squares algorithm is proposed for enhancing the parameter estimation accuracy based on the multi-innovation identification theory. The key is to derive two sub-identification models, each of which contains a set of merged parameter vectors. The proposed algorithm is effective and can generate highly accurate parameter estimates compared with the over-parametrization identification method, and can be easily extended to multi-input multi-output systems. Finally, an illustrative example is provided to verify the effectiveness of the proposed algorithm.

Hierarchical least squares parameter estimation algorithm for two-input Hammerstein finite impulse response systems

Quasi-two-dimensional (quasi-2D) perovskites have attracted extraordinary attention due to their superior semiconducting properties and have emerged as one of the most promising materials for next-generation light-emitting diodes (LEDs). The outstanding optical properties originate from their structural characteristics. In particular, the inherent quantum-well structure endows them with a large exciton binding energy due to the strong dielectric- and quantum-confinement effects; the corresponding energy transfer among different n-value species thus results in high photoluminescence quantum yields (PLQYs), particularly at low excitation intensities. The review herein presents an overview of the inherent properties of quasi-2D perovskite materials, the corresponding energy transfer and spectral tunability methodologies for thin films, as well as their application in high-performance LEDs. We then summarize the challenges and potential research directions towards developing high-performance and stable quasi-2D PeLEDs. The review thus provides a systematic and timely summary for the community to deepen the understanding of quasi-2D perovskite materials and resulting LED devices.

/pdf/high-performance-quasi-2d-perovskite-light-emitting-diodes-4c1sc6xsfq.pdf

High-performance quasi-2D perovskite light-emitting diodes: from materials to devices.

This paper considers the parameter identification problems of controlled autoregressive systems using observation information. According to the hierarchical identification principle, we decompose the controlled autoregressive system into two subsystems by introducing two fictitious output variables. Then a two-stage gradient-based iterative algorithm is proposed by means of the iterative technique. In order to improve the performance of the tracking the time-varying parameters, we derive a two-stage multi-innovation gradient-based iterative algorithm based on the multi-innovation identification theory. Finally, an example is provided to illustrate the effectiveness of the proposed algorithms.

Two-stage Gradient-based Iterative Estimation Methods for Controlled Autoregressive Systems Using the Measurement Data

This study considers the parameter estimation of a multi-variable output-error-like system with autoregressive moving average noise. In order to solve the problem of the information vector containing unknown variables, a least squares-based iterative algorithm is proposed by using the iterative search. The original system is divided into several subsystems by using the decomposition technique. However, the subsystems contain the same parameter vector, which poses a challenge for the identification problem, the approach taken here is to use the coupling identification concept to cut down the redundant parameter estimates. In addition, the recursive least squares algorithm is provided for comparison. The simulation results indicate that the proposed algorithms are effective.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-cta.2019.0112

Partially-coupled least squares based iterative parameter estimation for multi-variable output-error-like autoregressive moving average systems

High efficiency blue fluorescent organic light-emitting diodes (OLEDs), based on 1,3-bis(carbazol-9-yl)benzene (mCP) doped with 4,4’-bis(9-ethyl-3-carbazovinylene)-1,1’-biphenyl (BCzVBi), were fabricated using four different hole transport layers (HTLs) and two different electron transport layers (ETLs). Fixing the electron transport material TPBi, four hole transport materials, including 1,1-Bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC), N,N’-Di(1-naphthyl)-N,N’-diphenyl-(1,1’-biphenyl)-4’-diamine(NPB), 4,4’-Bis(N-carbazolyl)-1,1,-biphenyl (CBP) and molybdenum trioxide (MoO3), were selected to be HTLs, and the blue OLED with TAPC HTL exhibited a maximum luminance of 2955 cd/m2 and current efficiency (CE) of 5.75 cd/A at 50 mA/cm2, which are 68% and 62% higher, respectively, than those of the minimum values found in the device with MoO3 HTL. Fixing the hole transport material TAPC, the replacement of TPBi ETL with Bphen ETL can further improve the performance of the device, in which the maximum luminance can reach 3640 cd/m2 at 50 mA/cm2, which is 23% higher than that of the TPBi device. Furthermore, the lifetime of the device is also optimized by the change of ETL. These results indicate that the carrier mobility of transport materials and energy level alignment of different functional layers play important roles in the performance of the blue OLEDs. The findings suggest that selecting well-matched electron and hole transport materials is essential and beneficial for the device engineering of high-efficiency blue OLEDs.

/pdf/effects-of-charge-transport-materials-on-blue-fluorescent-30u0teg2zw.pdf

Effects of Charge Transport Materials on Blue Fluorescent Organic Light-Emitting Diodes with a Host-Dopant System.

High efficiency perovskite light-emitting diodes (PeLEDs) using PEDOT:PSS/MoO3-ammonia composite hole transport layers (HTLs) with different MoO3-ammonia ratios were prepared and characterized. For PeLEDs with one-step spin-coated CH3NH3PbBr3 emitter, an optimal MoO3-ammonia volume ratio (0.02) in PEDOT:PSS/MoO3-ammonia composite HTL presented a maximum luminance of 1082 cd/m2 and maximum current efficiency of 0.7 cd/A, which are 82% and 94% higher than those of the control device using pure PEDOT:PSS HTL respectively. It can be explained by that the optimized amount of MoO3-ammonia in the composite HTLs cannot only facilitate hole injection into CH3NH3PbBr3 through reducing the contact barrier, but also suppress the exciton quenching at the HTL/CH3NH3PbBr3 interface. Three-step spin coating method was further used to obtain uniform and dense CH3NH3PbBr3 films, which lead to a maximum luminance of 5044 cd/m2 and maximum current efficiency of 3.12 cd/A, showing enhancement of 750% and 767% compared with the control device respectively. The significantly improved efficiency of PeLEDs using three-step spin-coated CH3NH3PbBr3 film and an optimum PEDOT:PSS/MoO3-ammonia composite HTL can be explained by the enhanced carrier recombination through better hole injection and film morphology optimization, as well as the reduced exciton quenching at HTL/CH3NH3PbBr3 interface. These results present a promising strategy for the device engineering of high efficiency PeLEDs.

/pdf/improved-efficiency-of-perovskite-light-emitting-diodes-anfp510r5o.pdf

Improved Efficiency of Perovskite Light-Emitting Diodes Using a Three-Step Spin-Coated CH3NH3PbBr3 Emitter and a PEDOT:PSS/MoO3-Ammonia Composite Hole Transport Layer.

Organic light-emitting diodes (OLEDs) have drawn a great deal of attention due to their wide application in lighting and displaying. With the development of nanotechnology, surface plasmas have been widely used in photonics, microscopes, solar cells and biosensors. In this paper, by inserting graphene oxide (GO), Au nanoparticles (Au NPs) and GO/Au NPs composite structures between the hole transport layer (NPB) and indium tin oxide (ITO) anode respectively, the electroluminescent performance of Alq3-based OLEDs was significantly enhanced. Compared to the reference devices, the devices with the composite inserting layer containing 10% GO/Au NPs doping have the best electroluminescent performance, which have improved 47.9% in maximum luminance, 49.2% in maximum current efficiency and 45.3% in maximum external quantum efficiency (EQE), respectively. Such substantial enhancement of photoelectric performance can be attributed to the combined effects of LSPR coupling and the better hole transport property by introducing Au NPs and graphene oxide doped layer.

/pdf/plasmonic-enhanced-organic-light-emitting-diodes-based-on-a-2bi6t00xrb.pdf

Plasmonic-Enhanced Organic Light-Emitting Diodes Based on a Graphene Oxide/Au Nanoparticles Composite Hole Injection Layer

One Pot Synthesis of Sb2O3/Reduced Graphene Oxide Composite Anode Material for Sodium Ion Batteries

Organic–inorganic hybrid perovskites have attracted widespread attention in relation to light-emitting diodes (LEDs) due to their excellent properties. However, the imperfect energy band alignment between the perovskite and poly(3,4 ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) limits the device’s performance. Here, we have investigated the effect of blending MoS2 in PEDOT:PSS and the resulting performance of perovskite LEDs (PeLEDs). We found that the doping of MoS2 can optimize the energy barrier and promote hole injection, significantly improving the current efficiency (CE) of PeLEDs, which can be attributed to the distinguished electrical conductivity and improved charge injection balance. At the same time, the local surface plasmon resonance effect with Au nanoparticles (NPs) is also introduced to reduce the nonradiative recombination and effectively promote light emission to further improve the performance of PeLED devices. Compared to the control PeLEDs device with undoped PEDOT:PSS as the hole transport layer, a 223% enhancement in maximum CE and a 130% enhancement in maximum luminance are achieved, with an optimal volume ratio for the PEDOT:PSS:MoS2 of 1:0.4 and Au NPs of 10%. Thus, the optimization combination of MoS2 and Au NPs is an excellent approach to improve the performance of PeLEDs, thereby increasing the potential applications of PeLED devices.

Yan Jiang

Papers

Effects of Charge Transport Materials on Blue Fluorescent Organic Light-Emitting Diodes with a Host-Dopant System.

Improved Efficiency of Perovskite Light-Emitting Diodes Using a Three-Step Spin-Coated CH3NH3PbBr3 Emitter and a PEDOT:PSS/MoO3-Ammonia Composite Hole Transport Layer.

Plasmonic-Enhanced Organic Light-Emitting Diodes Based on a Graphene Oxide/Au Nanoparticles Composite Hole Injection Layer

One Pot Synthesis of Sb2O3/Reduced Graphene Oxide Composite Anode Material for Sodium Ion Batteries

High performance perovskite LEDs via SPR and enhanced hole injection by incorporated MoS 2