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

Abstract

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.

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

“…The methods proposed in this paper can combine some statistical optimal strategies [44][45][46][47] to study the parameter estimation algorithms of linear and nonlinear systems [48][49][50][51][52] and can be applied to other fields, [53][54][55][56][57][58][59] such as fault detection, image processing, and sliding mode control. [60][61][62][63]…”

The filtering‐based maximum likelihood iterative estimation algorithms for a special class of nonlinear systems with autoregressive moving average noise using the hierarchical identification principle

“…• The methods proposed in this paper can combine some statistical optimal strategies [47][48][49] to study the parameter estimation algorithms of linear and nonlinear systems [50][51][52][53][54][55][56] and can be extended to other fields. [57][58][59][60][61][62][63][64][65][66][67][68][69]…”

Adaptive parameter estimation for a general dynamical system with unknown states

“…In the future work, the further investigation includes the state estimation and parameter identification problem of linear and nonlinear time‐delay systems with colored noises and the convergence analysis of the algorithms involved. The proposed state filter–based recursive least squares algorithm for a general dynamical system with unknown states can combine other techniques and strategies to explore new state and parameter identification methods and can be applied to other fields such as information processing and communication …”

“…The proposed state filter-based recursive least squares algorithm for a general dynamical system with unknown states can combine other techniques and strategies [61][62][63][64] to explore new state and parameter identification methods and can be applied to other fields such as information processing and communication. [65][66][67][68][69]…”