Highly efficient double-doped solid-state white light-emitting electrochemical cells

Abstract

We report highly efficient, solid-state, white light-emitting electrochemical cells (LECs) based on a double-doped strategy, which judiciously introduces an orange-emitting guest, [Ir(ppy)₂(dasb)]⁺(PF₆⁻), into a single-doped emissive layer comprised of an efficient blue-green emitting host, [Ir(dfppz)₂(dtb-bpy)]⁺(PF₆⁻), and a red-emitting guest, [Ir(ppy)₂(biq)]⁺(PF₆⁻), to improve the balance of carrier mobilities and, thus, to enhance the device efficiency. Photoluminescence (PL) measurements show that the single-doped (red guest) and the double-doped (red and orange guests) host–guest films exhibit similar white PL spectra and comparable photoluminescence quantum yields, while the device efficiencies of the double-doped white LECs are twofold higher than those of the single-doped white LECs. Therefore, such enhancement of the device efficiency is rationally attributed to the improved balance of carrier mobilities of the double-doped emissive layer. Peak external quantum efficiency and peak power efficiency of the double-doped white LECs reached 7.4% and 15 lm W⁻¹, respectively. These efficiencies are amongst the highest reported for solid-state white LECs and, thus, confirm that the double-doping strategy is useful for achieving highly efficient white LECs.