Improving device efficiencies of solid-state white light-emitting electrochemical cells by adjusting the emissive-layer thickness

•Adjust the thickness of the emissive layer of white LECs to reduce exciton quenching.•Recombination zone positions of white LECs are estimated by employing microcavity effect.•High external quantum efficiencies and power efficiencies reach ca. 11% and 20 lm/W, respectively.

Exciton quenching in the recombination zone close to electrochemically doped regions would be one of the bottlenecks for improving device efficiencies of solid-state white light-emitting electrochemical cells (LECs). To further enhance device efficiencies of white LECs for practical applications, we adjust the emissive-layer thickness to reduce exciton quenching. In white LECs with properly thickened emissive-layer thickness, the recombination zone can be situated near the center of the emissive layer, rendering mitigated exciton quenching and thus enhanced device efficiencies. High external quantum efficiencies and power efficiencies of optimized devices reach ca. 11% and 20 lm/W, respectively, which are among the highest reported for white LECs. These results confirm that tailoring the thickness of the emissive layer to avoid exciton quenching would be a feasible approach to improve device efficiencies of white LECs.

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