Phosphorescent cuprous complexes (1–6) with general formula CuI(N^P) (PPh3), where N^P = 2-(2′-diphenylphosphinophenyl)-1-phenyl-5-methoxybenzimidazole derivatives, have been designed and synthesized. The crystal structures of the neutral four-coordinated Cu(I) complexes are determined by single crystal X-ray diffraction. At 293 K, these complexes exhibit intense phosphorescence with exceptionally high photoluminescence quantum yields (up to 88.3%) and short decay times (4.8–55.2 μs). The emission maxima can be fine-tuned from 529 nm to 577 nm, depending upon the number and position of methoxy substituent on the N^P ligand. Especially, complex 5 exhibits phosphorescence (533 nm) with photoluminescence quantum yield of 70.5% and decay time of 19.5 μs, implying its potential to serve as a phosphor for organic light emitting diode (OLED). Solution-processed OLED incorporating complex 5 as dopant emitter achieves a maximum brightness of 7729 cd with CIE coordinates (0.4351, 0.5398), constituting a step further toward the design of cuprous complexes as cheap and environmental alternatives to the luminescent noble metal complex.