Constructing Highly Efficient Blue OLEDs with External Quantum Efficiencies up to 7.5 % Based on Anthracene Derivatives

Abstract

Acquiring desirable device performance with deepblue color purity that fulfills practical application requirements is still a challenge. Bipolar fluorescent emitters with hybrid local and charge transfer (HLCT) state may serve to address this issue. Herein, by inserting anthracene core in the deep-blue building blocks, the authors successfully developed two highly twisted D-π-A fluorescent emitters, ICz-An-PPI and IP-An-PPI, featuring different acceptor groups. Both exhibited superb thermal stabilities, high photo luminescent quantum yields and excellent bipolar transport capabilities. The nondoped OLEDs using ICz-An-PPI and IP-An-PPI as the emitting layers showed efficient blue emission with an external quantum efficiency (EQE max ) of 4.32 % and 5.41 %, and the CIE coordinates of (0.147, 0.180) and (0.149, 0.150), respectively. In addition, the deep blue doped device based on ICz-An-PPI was achieved with an excellent CE max of 5.83 cd A À 1 , EQE max of 4.6 % and the CIE coordinate of (0.148, 0.078), which is extremely close to the National Television Standards Committee (NTSC) standard. Particularly, IP-An-PPI-based doped device had better performance, with an EQE max of 7.51 % and the CIE coordinate of (0.150, 0.118), which was very impressive among the recently reported deep-blue OLEDs with the CIE y < 0.12. Such high performance may be attributed to the hot exciton HLCT mechanism via T 7 to S 2 . Our work may provide a new approach for designing high-efficiency deepblue materials.

Impact of peripheral groups on pyrimidine acceptor-based HLCT materials for efficient deep blue OLED devices

“…1 H NMR and 13 C NMR spectra were measured on a Bruker AVANCE III (400 MHz) spectrometer where tetramethyl silane was used as an internal reference for chloroform deuteride. Ultraviolet-visible (UV-vis) absorption and photoluminescence (PL) spectra were recorded on a Thermo Evolution 300 and a FluoroMax-4 spectrophotometer, respectively.…”

“…† The synthesized FlCz and SFCz (Fig. 1a) were fully characterized by MALDI-TOF mass spectroscopy, 1 H NMR spectroscopy, and 13 C NMR spectroscopy (Fig. S2-S6, ESI †).…”

“…Subsequently, a series of light-emitting molecules based on PPI were reported by changing the substituents at the 1 and 2 positions of imidazole. 3,[6][7][8][9][10][11][12][13][14][15][16][17][18] However, the class of PPI acceptors is relatively single, significantly limiting the development of such materials. Although some other acceptors, 19 such as pyrene-imidazole 20,21,[22][23][24] and 9,10-diphenylimidazole, [25][26][27] have been developed, there is still a need to develop more effective acceptor planes for expanding this HLCT material system.…”

Deep-blue high-efficiency triplet–triplet annihilation organic light-emitting diodes using hydroxyl-substituted tetraphenylimidazole-functionalized anthracene fluorescent emitters

“…13,14 Since TTA molecules based on 4-cyanophenyl anthracene fragment have been fully investigated, in this work, we would like to propose a new approach for designing anthracene-based deep-blue TTA emitters. 15 Hence, two new anthracene derivatives, namely HO-PIAC and PIAC , were specifically designed and successfully synthesized (Scheme 1). In these models, the anthracene as a TTA core was asymmetrically functionalized at the 9,10 positions with ( N -phenylcarbazol-3-yl)phenyl and two different tetraphenylimidazoles.…”

Phenanthrene-based deep-blue fluorophores with balanced carrier transport ability for high-performance OLEDs with a CIEy< 0.04

“…27,28 In the past decade, numerous multifunctional D-A type bipolar materials have been developed as deep-blue emitters for FOLEDs and as hosts for PhOLEDs. [29][30][31][32] Among them, electron-deficient units such as pyridine, 33 phenantroimidazole, 34,35 cyano 25,44 and anthracene 36 were widely employed for the preparation of deep-blue luminogens. Tang et al recently reported four twisted D-A type deep-blue fluorophores by employing electron-deficient 1-phenyl-1H-imidazo-[4,5-c]pyridine and various electron-rich moieties.…”