Fig. 4
Device optimization and large-area fabrication. a The measured current efficacy (solid black squares) and power conversion efficacy (open red circles) as a function of the current density for the host–guest LEC, with a guest concentration of 29% and with the PVK:OXD-7 blend host. b The current efficacy (left) and external quantum efficiency (right) as a function of guest concentration for the ITO/PEDOT:PSS/PVK:OXD-7:Ir(R-ppy)3:THABF4/Al LEC (solid black squares) and a ITO/PEDOT:PSS/PVK:OXD-7:Ir(R-ppy)3/Ca/Al OLED (open red circles). The devices featured the same active-material thickness (130 nm) and were driven by j = 7.7 mA cm−2. c The simulated steady-state concentration profiles for a host–guest OLED, with realistic injection barriers for electrons (0.2 eV) and holes (0.5 eV). d The simulated steady-state concentration profiles for a host–guest LEC with an injection barrier of 1 eV for both electron and hole injection. Both devices feature symmetric trap depths and mobilities, and the symbols are identified in Fig. 1c. e The initial evolution of the luminance (left axis) and the current efficacy (right axis) of pristine ITO/PEDOT:PSS/PVK:OXD-7:Ir(R-ppy)3:THABF4/Al LECs featuring a thin film comprising a hexagonal array of hemispherical microlenses (MLA-LEC, open circles) or a glass half sphere (GHS-LEC, solid squares) as the outcoupling structure. Both LECs were driven by a current density of j = 1.9 mA cm−2. f The uniform green light-emission from a 45 cm2 large-area host–guest LEC fabricated by spray-sintering under ambient air. Inset: photograph depicting the airbrush performing spray-sintering deposition
