Horizontal orientation of a linear-shaped platinum(II) complex in organic light-emitting diodes with a high light out-coupling efficiency

A linear-shaped phosphorescent platinum(II) complex that adopts a horizontal orientation in amorphous films was synthesized. The complex possesses a photoluminescence quantum efficiency of φ_PL = 50 ± 3% in thin films with the host of m-biscarbazolylbenzene and 4,4′- bis(Ncarbazolyl) biphenyl. Polarized emission from the edge of these thin films confirmed the horizontal orientation of the complex within them. An organic light-emitting diode containing the complex possessed a maximum external quantum efficiency of η_EQE = 15:8 ± 3%. The light outcoupling efficiency of the device was estimated to be at least φ_out = 32 ± 3%, which was ascribed to the horizontal orientation of the complex.