Aggregation-induced emission tetraphenylethene type derivatives for blue tandem organic light-emitting diodes

Tetraphenylethene (TPE) has been demonstrated to be an effective core molecule for generating excellent aggregation-induced emissions (AIE). Herein, we propose TPE moieties decorated with different biphenyl or anthracenyl fragments to avoid the crystallization of neat film and simultaneously harvest blue AIE. The two synthesized compounds, 2-(4-biphenyl)-1,1,2-triphenylethylene (2) and 2-(9-antracenyl)-1,1,2-triphenylethylene (3), possess bipolar transport capabilities, high thermal stability, and strong sky-blue AIE. Both compounds 2 and 3 were selected as emitters to investigate their electroluminescence applications. The optimized nondoped sky-blue organic light-emitting diodes (OLEDs) with 2 and 3 exhibited respective maximum efficiencies of 3.8% (8.8 cd/A) and 2.2% (4.0 cd/A). These results illustrate the effective molecular design concepts of the TPE derivatives containing biphenyl or anthracenyl fragments. Furthermore, a tandem device architecture was used to improve device efficiency. Through adopting the specific designs of the intermediate charge generation layer structure and the corresponding device architecture, respective peak efficiencies of 8.2% (19.4 cd/A) and 4.6% (9.5 cd/A) were obtained in tandem devices with 2 and 3 emitters together with slight efficiency roll-off. The superior EL performance demonstrated that the tandem structure possesses high potential for boosting the efficiency of the AIE-based OLEDs.