Manipulating the Molecular Backbone to Achieve Highly Emissive Sky‐Blue AIEgens and Their Applications in Nondoped Organic Light‐Emitting Diodes

Abstract To enhance the luminescent performance of aggregation‐induced emission luminogens (AIEgens) in organic light‐emitting diodes (OLEDs) but also retain their blue emission color, 2‐CzTPE and 2,7‐CzTPE with promising AIE features are synthesized to balance the trade‐off between twisted molecular conformation and enlarged molecular conjugation. As observed, although 2‐CzTPE, which contains twisted molecular backbone, could suppress the emission‐quenching π–π stacking, an inferior luminescent performance with photoluminescence quantum yields (PLQYs) of 23.12% occurs in aggregated solid state for its limited molecular conjugation, then leading to an inferior electroluminescence (EL) performance with external quantum efficiency (EQE) of 1.9%. However, after molecular engineering of backbone to enlarge its conjugation in 2,7‐CzTPE, significantly enhanced PLQY value of 60.63% is achieved in solid state. Interestingly, the emission of 2,7‐CzTPE remains in the blue region, which is even identical to that of 2‐CzTPE in aggregates. Finally, much better EL performance in nondoped OLEDs with current efficiency of 7.38 cd A −1 , power efficiency of 6.81 lm W −1 , and also EQE of 3.0% is achieved for 2,7‐CzTPE‐based devices. These findings demonstrate that manipulating molecular backbone to achieve the balanced molecular conjugation and twisted conformation is an efficient way to obtain highly emissive blue AIEgens in both aggregated state and OLEDs devices.