Solution processible imidazole-based iridium dendrimers with oligocarbazole for nondoped phosphorescent OLEDs
摘要:
By introducing t-butyl- or methoxyl-containing oligocarbazole into the periphery of tris(mesityl-2-phenyl-1H-imidazole)iridium (III) [Ir (mpim)(3)], two novel imidazole-based Ir dendrimers Bu-t-D2-Ir (mpim)(3) and MeO-D2-Ir (mpim)(3) have been designed and synthesized through a convenient post-dendronization route. Due to the effective encapsulation, the intermolecular interactions and thus luminescence quenching in solid states is found to be gradually reduced following a sequence of Ir (mpim)(3) > MeO-D2-Ir (mpim)(3) > Bu-t-D2-Ir (mpim)(3). Compared with the bare Ir (mpim)(3) core (Phi(PL) = 0.38 and tau = 0.26 mu s), accordingly, the film photoluminescence quantum yield and excited state lifetime are improved to 0.54 and 0.39 mu s for MeO-D2-Ir (mpim)(3) and 0.88 and 1.09 mu s for Bu-t-D2-Ir (mpim)(3). When these developed Ir dendrimers are adopted as the emitting layer alone, Bu-t-D2-Ir (mpim)(3) achieves an excellent nondoped device performance, revealing a maximum current efficiency as high as 35.7 cd/A (13.2%, 37.4 lm/W) together with Commission Internationale del_Eclairage coordinates of (0.21, 0.45). Even at a high luminance of 1000, 5000 and 10000 cd/m(2), it still remains to be 27.8, 24.7 and 21.8 cd/A, respectively, indicative of the gentle efficiency roll-off. The result clearly demonstrates the great potential of imidazole-based Ir dendrimers used for efficient nondoped phosphorescent organic light-emitting diodes.
Organic light emitting materials and devices comprising phosphorescent metal complexes comprising ligands comprising aryl or heteroaryl groups substituted at both ortho positions are described. An organic light emitting device, comprising: an anode; a hole transport layer; an organic emissive layer comprising an emissive layer host and an emissive dopant; an electron impeding layer; an electron transport layer; and a cathode disposed, in that order, over a substrate.
Organic light emitting materials and devices comprising phosphorescent metal complexes comprising ligands comprising aryl or heteroaryl groups substituted at both ortho positions are described. An organic light emitting device, comprising: an anode; a hole transport layer; an organic emissive layer comprising an emissive layer host and an emissive dopant; an electron impeding layer; an electron transport layer; and a cathode disposed, in that order, over a substrate.