Efficient piezochromic luminescence from tetraphenylethene functionalized pyridine-azole derivatives exhibiting aggregation-induced emission

In this work, three tetraphenylethene-functionalized pyridine-azole derivatives were successfully synthesized and characterized. Their photophysical properties in both solution and solid-state were investigated systematically. All luminogens are almost non-emissive in solution but highly emissive in the aggregated states, showing aggregated-induced emission. Importantly, their crystalline aggregates exhibit effective piezochromism with high contrast in both emission color and intensity. The emission color between blue and green can be reversibly and quickly switched by a grinding-heating process several times without any deterioration. The experimental data clearly demonstrate that the interconversion between crystalline and amorphous states is response for the present piezochromism. Non-doped electroluminescence devices using the dyes as light-emitting layers were fabricated. The devices display a peak current efficiency of 2.3 cd A(-1) and power efficiency of 2.0 lm W-1, respectively. The obtained results will be useful in designing new efficient multifunctional materials and enriching piezochromic luminescent systems as well. (C) 2015 Elsevier Ltd. All rights reserved.