Research Paper: Determining the Width of the Dynamic Emission Zone in Light-Emitting Electrochemical Cells

Scientific Summary

This study introduces a novel method to determine the dynamic width and position of the emission zone (EZ) in light-emitting electrochemical cells (LECs), addressing a critical but challenging aspect for understanding device performance. The EZ's characteristics profoundly influence emission losses, outcoupling efficiency, and drive voltage. The method involves fitting simulated angle-resolved s-polarized electroluminescence (EL) spectra to measured data, treating EZ width and position as adjustable parameters.

Key findings reveal that the EZ width decreases during initial LEC operation and further narrows with increasing current density. At steady state and 10 mA cm⁻², the EZ width is approximately 20% of the active-material thickness. This understanding is vital because a decreasing EZ width correlates with increased exciton quenching and efficiency roll-off. The insights gained are crucial for identifying loss channels and enabling the rational design of improved, more efficient LEC devices.

Publication Details

Zhang, X., Ràfols-Ribé, J., Kirch, A., Larsen, C., & Edman, L. (2025), Determining the Width of the Dynamic Emission Zone in Light-Emitting Electrochemical Cells. Advanced Optical Materials. https://doi.org/10.1002/adom.202501128.

Fluxim Tools Used

The study utilized the commercial software Setfos for optical modeling and simulation. Setfos was instrumental in simulating the LEC device structure, doping, and exciton generation profiles. Its primary benefit was enabling the accurate fitting of simulated angle-resolved EL spectra to measured experimental data by treating EZ position (x0) and width (w0=6σ) as free parameters. This capability allowed for the precise determination of these elusive, dynamic device parameters, which are difficult to measure directly, and validated the methodology through Mean Absolute Error (MAE) analysis.