Effective Europium Coordination Luminophores Linked with Bi- and Tridentate Carbazole Phosphine Oxides for Organic Electroluminescent Devices

摘要

Lanthanide coordination polymers with charge combination parts, hole and electron transport units, [Eu(ntfa)(3)(dppcz)](n) and [Eu-3(ntfa)(9)(tpcz)(2)](n) [ntfa = 3-(2-naphthoyl) -1,1,1- trifluoroacetonate, dppcz = 3,6-bis(diphenylphosphoryl)-9-phenylcarbazole), tpcz = 3,6-bis(diphenylphosphoryl)-9-[4-(diphenylphosphoryl)phenyl] carbazole], are reported as an emitting material for organic electroluminescent (EL) devices. The intrinsic emission quantum yields Phi(4f)(-)(4f) of [Eu(ntfa)(3)(dppcz)](n) and [Eu-3(ntfa)(9)(tpcz)(2)](n) in the solid state were calculated to be 32% and 45%, respectively. The photosensitized energy-transfer efficiencies eta(sens) from organic ntfa ligands to luminescent Eu(III) ions in [Eu(ntfa)(3)(dppcz)](n) and [Eu-3(ntfa)(9)(tpcz)(2)](n) were found to be 84% and 39%, respectively. The energy-transfer efficiency eta(sens)from ntfa to Eu(III) ion is dependent on the network structure in Eu(III) coordination polymers in the solid state. The eta(sens) values and characteristic structures of Eu(III) coordination polymers are directly linked to maximum luminances and current efficiencies in solid EL devices, respectively. The luminance of an EL device containing [Eu(ntfa)(3)(dppcz)](n) was estimated to be 188 cd/m(2) at 15 V, which is greater than that of previously reported EL devices with Eu(III) complexes.