Figure 1. Design overview of proposed high-efficiency graphene-based OLEDs.

(a) Schematic device structure of the proposed OLEDs. (b) Electromagnetic field intensity distribution (dashed lines) of the OLEDs under study for their respective first-order cavity design. The field-intensity distribution of the graphene-based OLED without TiO₂ is also shown for comparison for the case where the thickness values of organic layers are same as the OLEDs with TiO₂ but without low-index HILs. (c,d) Calculated maximum external quantum efficiency (η_EQE) of graphene-based OLEDs with TiO₂ under-layer as a function of TiO₂ and organic layer thickness (d_TiO2 and d_org, respectively). Dashed lines represent contour lines for η_EQE of 10, 20, 30 or 40% as indicated in the graph. (c) Without a low-index HIL; (d) with GraHIL as a low-index HIL. On the bottom of each case, the reflectance (R_bot) from the bottom electrode assembly (TiO₂/graphene/(HIL)) as a whole is presented as a function of d_TiO2 for light incident from the organic layers.