Triphenylethene-carbazole-based molecules for the realization of blue and white aggregation-induced emission OLEDs with high luminance

Abstract

Molecules that use triphenylethene-carbazole moieties decorated with different substitutions were designed and synthesized, harvesting wide energy bandgaps and aggregation-induced emission (AIE) characteristics. The photophysical, thermal, and electroluminescence (EL) characteristics of the designed emitters were investigated to clarify the molecular structure-property-performance relationship. The photoluminescence spectra of the synthesized molecules measured using tetrahydrofuran-water solution presented strong blue emissions, confirming their AIE property. The doped blue-emitting organic light-emitting diodes (OLEDs) with compound 2 exhibited satisfactory peak efficiency of 8.7 cd/A and high maximum luminance of 18474 cd/m2. In comparison, the peak efficiency of the 2-based sky-blue OLEDs with a non-doped emitting layer was 10.2 cd/A with an even superior peak luminance of 39661 cd/m2. Blue-emitting AIE OLEDs have rarely presented such high luminance values, and this improvement can facilitate the development of white-emitting OLEDs (WOLEDs) for lighting applications. The fabricated WOLEDs with 2 achieved a maximum efficiency of 5.6% (8.0 cd/A and 7.5 lm/W), stable EL spectra, and high luminance of 29319 cd/m2. These results indicate that the triphenylethene-carbazole structure designs for AIE molecules could simultaneously harvest wide energy bandgap and high luminance, demonstrating their high potential for EL applications.