Non-doped blue organic light emitting devices based on tetraphenylethylene-π-imidazole derivatives

Three tetraphenylethylene (TPE) conjugates 3a-3c were designed and synthesized for non-doped blue organic light emitting diodes, where aryl imidazoles of phenanthrene, phenanthroline, and pyrene were coupled with TPE. The single crystal structures of 3a and 3c show twisted molecular geometry and the crystal packing of 3c exhibits tight packing compared to 3a. The thermal, photophysical, electrochemical and computational properties of 3a-3c were investigated. The TPE conjugates 3a-3c show good thermal stability upto 424 degrees C. All the TPE conjugates 3a-3c exhibit excellent aggregation induced emission (AIE) and fluorescence of 3a, 3b and 3c in aggregated suspension was enhanced by 9, 9 and 38 folds compared to fluorescence in THF solution, respectively. 3a and 3c were efficient as the non-doped fluorescent emitters and provided high quantum efficiency/current efficiency of 5.6%/11.1 cd/A and 5.0%/9.4 cd/A in the blue devices, respectively. The color coordinates of the 3a and 3c devices were (0.19, 0.31) and (0.18, 0.26), respectively. (C) 2016 Published by Elsevier B.V.