Inverted top-emitting organic light-emitting diodes (ITOLEDs) with aluminum as cathode and semitransparent silver as
anode are investigated. Comparing the blue, green and red ITOLEDs with conventional BEOLEDs based on iridium
complex, it is surprising that the red ITOLED exhibits a higher efficiency nearly twice as that of the bottom-emitting
counterpart, while blue and green ITOLEDs are comparable to BEOLEDs. We explain that the role of the strong
microcavity effect improved the spontaneous emission of emitters in all ITOLEDs, however, only the intrinsic quantum
yield of the red emitters is improved due to its comparable radiative and nonradiative decay rates.