Multifunctional luminophores with dual emitting cores: TADF emitters with AIE properties for efficient solution- and evaporation-processed doped and non-doped OLEDs

Three novel emitters with dual emitting cores, namely 3,3 & PRIME;,5,5 & PRIME;-tetra(triphenylamine-4-yl)-[1,1 & PRIME;-biphenyl]-2,2 & PRIME;,6,6 & PRIME;-tetracarbonitrile (DDTPAIPN), 3,3 & PRIME;-di(triphenylamine-4-yl)-5,5 & PRIME;-di(3,5-(9,9 & PRIME;-dicarbazolyl)phenyl)-[1,1 & PRIME;- biphenyl]-2,2 & PRIME;,6,6 & PRIME;-tetracarbonitrile (DTPAmCPIPN), and 3,3 & PRIME;,5,5 & PRIME;-tetra(3,5-(9,9 & PRIME;-dicarbazolyl)phenyl)-[1,1 & PRIME;- biphenyl]-2,2 & PRIME;,6,6 & PRIME;-tetracarbonitrile (DDmCPIPN) are designed and synthesized by coupling their respective single core emitters. Compared with their single core counterparts, the three novel compounds exhibit significantly improved thermal stability, absorption coefficients, and photoluminescence efficiencies in neat films. Photophysical measurements show that these three emitters exhibit both aggregation-induced emission and thermally activated delayed fluorescence properties, which is beneficial for non-doped organic light-emitting diodes (OLEDs). The new compounds show relatively balanced charge carrier transport abilities as revealed by unipolar devices. The solution-and evaporation-processed doped and non-doped OLEDs made from these three luminophores achieve excellent electroluminescence (EL) performances. The peak current, power, and external quantum efficiencies of a DTPAmCPIPN-based solution-processed doped device reach 59.2 cd A(-1), 61.3 lm W-1, and 17.2%, respectively, with an emission peak at 548 nm. The evaporation-processed doped device based on DTPAmCPIPN exhibits maximum EL efficiencies of up to 63.7 cd A(-1), 61.1 lm W-1, and 19.2%. Moreover, the non-doped OLEDs also possess superior EL efficiencies with extremely small efficiency roll-offs. The molecular design strategy in this work is demonstrated to be effective in developing new emitters for efficient and stable OLEDs.