Highly efficient blueish-green fluorescent OLEDs based on AIE liquid crystal molecules: from ingenious molecular design to multifunction materials

Abstract

ABSTRACT:In order to seek the balance point between liquid crystalline and high efficiency emission, two novel aggregation-induced emission-based (AIE) liquid crystal materials of TPE-PBN and TPE-2PBN, which contains tetraphenylethene derivative as the emission core and 4-cynobiphenyl moiety as the mesogenic unit, were designed and prepared. Both simple molecules showed a mesophase at high temperature evidenced by polarised optical microscopy (POM), differential scanning calorimetry (DSC) and temperature-dependent X-ray diffraction (XRD).Simultaneously, TPE-PBN and TPE-2PBN presented clearly AIE characteristics in the blueishgreen region and achieved the high emission quantum efficiency of 71% and 83% in solid state, respectively. Due to the self-assembly property of thermotropic liquid crystals, both compounds showed higher hole mobilities in the annealed films than in pristine films. Employing TPE-PBN and TPE-2PBN as the emitting materials, both non-doped devices and doped devices were fabricated. The TPE-PBN-based doped OLEDs showed a better device performance with an external quantum efficiency (EQE) of 4.1% which is among the highest EQE of the blue AIE fluorescent OLEDs.

A Facilely Synthesized Dual‐State Emission Platform for Picric Acid Detection and Latent Fingerprint Visualization

“…To overcome this issue, in 2001, Ta ng and co-workersp roposed an ew concept of "aggregation-induced emission" (AIE), [26] in which AIE luminogens (AIEgens) usually exhibit no or poorly emissivec haracteristics in dilute solution, but emit intensely in the aggregated state. [27][28][29][30][31] By using these highly emissive AIEgens, dual-state emission can be easily achieved and they have potential real-world applications, [32][33][34] such as in PA detection and LFP visualization. Recently,f lexible alkyl chains were introduced into conventionalf luorescent molecules to prevent close packing of their core structures as well as strong p-p intermolecular stacking interactions, [35][36][37] thereby openingr adiative channels to afford highlye missive features in aggregates.T herefore, based on these considera-tions, to achieve ah ighly efficient dual-state emission platform for PA detection and LFP visualization,i nt his work, flexible alkyl chains were facilelya ttached to the commercial organic dye 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA)t o afford the tetraalkyl 3,4,9,10-perylenetetracarboxylate target compounds PTCA-C4, PTCA-C6, and PTCA-C12 (fort he structures, see Figure 1).…”

Recent Developments in AIEgens for Non‐doped and TADF OLEDs

“…Wang et al. also synthesized two novel TPE derivatives, with obvious AIE characteristics in the blue‐green region and they were applied to fabricate non‐doped OLED.…”

Platinum-based metallomesogens bearing a Pt(4,6-dfppy)(acac) skeleton: synthesis, photophysical properties and polarised phosphorescence application

“…The increased absorption intensity at 327 nm for complex Pt2 originates from the additional TPE unit 1 π-π* transition. 45,46 Compared to complex Pt1, complex Pt2 possesses a red-shift absorption spectrum owing to its extended conjugation coursed by the conjugated TPE unit.…”