Peripheral aryl-substituted pyrrole fluorophores for glassy blue-light-emitting diodes

In this work, a series of aryl-substituted pyrrole analogues were synthesized. These pyrrole analogues emit violet to blue light. Fluorescence and amorphous glassy properties of these pyrrole analogues were induced by manipulating the peripheral aryl groups. These crowded peripheral aryl groups would effectively prevent the fluorophores from aggregation, resulting in higher quantum efficiency and a stable emission spectrum in the solid state. One of the aryl-substituted pyrrole analogues, namely NPANPy can be used as hole-transporting material or hole-transporting/emitting material. The devices would emit blue light when the fluorophore NPANPy acts as the hole-transporting/ emitting material. Their CIE coordinate is around (0.16, 0.14), whereas the maximum brightness can reach 4300-5000 cd m(-2). Apart from that, when the fluorophore was used only as the hole-transporting material, better device performances, especially in low current density, were found, as compared with the standard device. (C) 2007 Elsevier Ltd. All rights reserved.