the optical transparency of their constituents. The optical response of such dielectric photonic crystals (DPCs) is governed by the interference of partial reflections at the dielectric interfaces. [3] Metal-dielectric photonic crystals (MDPCs) are a class of hybrid photonic structures that incorporate both metals and dielectrics in their periodicity and exhibit unique properties owing to the complex permittivity of the metallic layers. We have previously demonstrated control of these principles by examining the behavior of electricallypumped, discrete MDPCs consisting of multiple stacked organic light emitting diode (OLED) microcavities. [4] The optically dissimilar metal electrodes in that work led to a broadening of the photonic states and a Peierls photonic bandgap due to the doubled unit cell. Here, we investigate methods for eliminating this effect by forming higher-symmetry single-cavity unit cell (unitary) MDPCs without employing identical metals in the interest of enabling efficient charge injection.The optical behavior of an MDPC is driven primarily by the resonant response of the constituent microcavities. [5][6][7] The resonant states of metallic microcavities undergo hybridization through interaction with adjacent cavities, facilitated by photon tunneling through the semi-transparent mirrors as illustrated in Figure 1. [8,9] This process is analogous to the formation of energy bands in atomic crystals, molecules, and coupled mechanical and optical resonators. [10][11][12] Indeed, this same effect can be observed in coupled Bragg microcavities which employ dielectric mirrors. [13][14][15] The Bragg microcavity produces states with narrower linewidth compared to the metallic microcavity at the cost of occupying roughly an order of magnitude more physical space, as illustrated in Figure 1a. An MDPC of the same size as a single Bragg microcavity offers a rich photonic band structure. This band structure can equivalently be described as a perturbative effect on the states defined by the outermost mirrors which represent the boundaries of the crystal, as illustrated in Figure 1b. The hybridization and perturbation models both lead to the observation that when two cavities are stacked the single cavity mode splits into a higher and lower energy mode, as in Figure 1c, with each additional cavity contributing another state to the band. [4,6,13,14,16] The properties of the photonic band depend sensitively on the optical properties of the metallic mirrors through the Vertically-stacked organic light emitting diode (OLED) microcavities form 1D metal-dielectric photonic crystals (MDPC) with many degrees of freedom for engineering complex emission profiles. The photonic band structure of the MDPC OLED is determined by the underlying unit cell and is particularly sensitive to the properties of the metallic electrodes. The electronic requirements of microcavity OLED fabrication often necessitate dissimilar metallic electrodes to achieve good performance. This can profoundly impact the photonic properties of a MDPC b...
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