Naphthalene-substituted 2,3,4,5-tetraphenylsiloles: Synthesis, structure, aggregation-induced emission and efficient electroluminescence

Two thermally stable naphthalene-substituted 2,3,4,5-tetraphenylsiloles, 1,1-dimethyl-2,5-bis[4-(naphthalen-1-yl)phenyl]-3,4-diphenylsilole (D-1-NpTPS) and 1,1-dimethyl-2,5-bis[4-(naphthalen-2-yl)phenyl]-3,4-diphenylsilole (D-2-NpTPS), have been synthesized and fully characterized. D-2-NpTPS shows redder absorption and emission than D-1-NpTPS due to the better conjugation between naphthalen-2-yl groups and phenyl rings at the 2,5-positions of the silole core. While they are weakly fluorescent in solutions, strong luminescence is induced when aggregated in poor solvents or fabricated into solid films, with high fluorescence quantum yields up to 99%, demonstrating their aggregation-induced emission (AIE) feature. Efficient non-doped organic light-emitting diodes utilizing D-1-NpTPS and D-2-NpTPS as light-emitting layers are fabricated. Remarkably high electroluminescence efficiencies of 10.5 cd A^-1, 7.3 lm W^-1, and 3.2% are acheived by the D-2-NpTPS device.