Hole-transporting and emitting pendant polymers for organic electroluminescent devices

Abstract

ABSTRACT New hole-transporting pendant polymers with high glass- transition temperatures (Tgs) above 200 oC were designed and synthesized. Multilayer organic electrolu minescent (EL) devices using the new polymers as the hole-transport layer and quinacridone-doped tris(8-quinolinolato)aluminum as the emitting layer exhibited high performance. One of the hole-transporting polymers functioned well as a hole injection buffer layer in organic EL devices. New green- and orange-emitting penda nt polymers with high Tgs and desired ambipolar character were also designed and synthesized. Organic EL devices using these emitting polymers also exhibited good performance. One of the hole-transporting polymer showed a high hole carrier mobility of over 10 i 3 cm 2 V i 1 s i 1 at an electric field of 1.0 × 10 5 Vcm i 1 , as determined by a time-of-flight method. Keywords : non-conjugated pendant polymers, hole-transpor ting polymers, emitting polymers, hole-injection buffer layer, hole-transport layer, hole drift mobility 1. INTRODUCTION S -Conjugated polymers have received a great deal of attention as materials for electronics and optoelectronics, and have been the subject of recent extensive studies. On the other hand, non-conjugated polymers containing pendant S -electron systems generally have the following characteristic features; a variety of S -electron systems with various functions for pendant groups, chemical stability, solubility in organic solvents, processability such as film-forming capability, and the invariance of oxidation and reduction potentials irrespective of the doping degree. We have performed a series of studies on non-conjugated polymers containing pendant S -electron systems in the light of the consideration that such polymers also constitute a new class of photo- and electroactive materials for electronic, optoelectronic, and photonic devices, permitting the formation of large-area homogeneous films with mechanical strength by wet processes. We have developed several classes of photo-and electroactive pendant polymers. They include electrically conducting polymers, which have found applications as electrode materials for secondary