Fig. 3. Modulation of the density of states through decreasing mirror thickness.

a Experimental emission spectra of six-cavity stacked OLED devices with mirror thickness of d = 30 → 10 nm. b Bandwidth of the resolved peaks as measured between the highest energy state to the first harmonic (second lowest). The fundamental mode of the crystal was not experimentally resolvable for d < 30 nm and was omitted for the bandwidth calculation. c Average energy separation between states in the upper sub-band. Energy separation increases with decreasing d due decreased perturbation of the extended cavity states. d Comparison of experimentally observed and simulated peak locations for d = 30 → 10 nm. Decreasing d is shown to result in a lower density of states through an increase in the photonic band-gap and the separation between states.