1. Efficiency Roll-Off in Light-Emitting Electrochemical Cells
- Author
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Zhang, X., Ràfols-Ribé, J., Mindemark, J., Tang, S., Lindh, E Mattias, Gracia-Espino, E., Larsen, C., Edman, L., Zhang, X., Ràfols-Ribé, J., Mindemark, J., Tang, S., Lindh, E Mattias, Gracia-Espino, E., Larsen, C., and Edman, L.
- Abstract
Understanding “efficiency roll-off” (i.e., the drop in emission efficiency with increasing current) is critical if efficient and bright emissive technologies are to be rationally designed. Emerging light-emitting electrochemical cells (LECs) can be cost- and energy-efficiently fabricated by ambient-air printing by virtue of the in situ formation of a p-n junction doping structure. However, this in situ doping transformation renders a meaningful efficiency analysis challenging. Herein, a method for separation and quantification of major LEC loss factors, notably the outcoupling efficiency and exciton quenching, is presented. Specifically, the position of the emissive p-n junction in common singlet-exciton emitting LECs is measured to shift markedly with increasing current, and the influence of this shift on the outcoupling efficiency is quantified. It is further verified that the LEC-characteristic high electrochemical-doping concentration renders singlet-polaron quenching (SPQ) significant already at low drive current density, but also that SPQ increases super-linearly with increasing current, because of increasing polaron density in the p-n junction region. This results in that SPQ dominates singlet-singlet quenching for relevant current densities, and significantly contributes to the efficiency roll-off. This method for deciphering the LEC efficiency roll-off can contribute to a rational realization of all-printed LEC devices that are efficient at highluminance., The authors wish to acknowledge generous financial support from the Swedish Research Council (2019‐02345 and 2021‐04778), the Swedish Energy Agency (50779‐1 and P2021‐00032), “Bertil och Britt Svenssons stiftelse för belysningsteknik,” Kempe Foundations, the Knut and Alice Wallenberg Foundation for a Proof of concept grant (KAW 2022.0381), the Wallenberg Initiative Materials Science for Sustainability (WISE) funded by the Knut and Alice Wallenberg Foundation (WISE‐AP01‐D02), and the European Research Council for an ERC Advanced Grant (project 101096650).
- Published
- 2024
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