An organic light emitting device (OLED) is provided, including a first organic electroluminescent cell, a second organic electroluminescent cell, a charge generation layer, disposed between the first and second organic electroluminescent cells, a first electrode and a second electrode formed at the first and second organic electroluminescent cells. The first organic electroluminescent cell comprises a fluorescent light emitting layer emitting a first light with wavelength substantially ranged from 430 nm-490 nm and a phosphorescent light emitting layer emitting a second light with wavelength substantially ranged from 602 nm-615 nm. The second organic electroluminescent cell comprises at least one light emitting layer emitting a third light with wavelength substantially ranged from 520 nm-550 nm. The color rendering index R9 formed by spectra combination from the first and second organic electroluminescent cells is larger than 0.