Research Paper: White light-emitting electrochemical cells based on metal-free TADF emitters
Device performance of thewhite TADF-LEC
Scientific Summary
The main goal of this study was the pioneering demonstration of a white light-emitting electrochemical cell (LEC) based solely on metal-free, thermally activated delayed fluorescence (TADF) emitters. This addresses drawbacks of current white LECs, which either use non-sustainable metals or are limited by converting only singlet excitons to photons. TADF materials can harvest both singlet and triplet excitons for light emission and are metal-free, offering a sustainable alternative.
Key findings reveal that a high-quality white TADF-LEC was realized through careful tuning of energy-transfer processes and the electrochemically formed doping structure within a single-layer active material. The device emits angle-invariant white light with a high color rendering index (CRI) of 88 and an external quantum efficiency (EQE) of 2.11% at a luminance of 350 cd/m². The broadband emission spectrum remains essentially unaffected by viewing angle, current density, and operational time.
Publication Details
Tang, S., Tsuchiya, Y., Wang, J., Adachi, C. and Edman, L. (2025), White light-emitting electrochemical cells based on metal-free TADF emitters. Nature Communications, [N/A]: Article 55954-3. https://doi.org/10.1038/s41467-025-55954-3
Fluxim Tools Used
The commercial software Setfos was used to determine the position of the "emissive p-n junction" in the active material, or more specifically, the average position of exciton generation. This was achieved by a combined measurement and simulation of the angle-dependent electroluminescence (EL) spectrum and intensity. The active material was simulated as transparent with a wavelength-dependent refractive index, and the distribution of emissive dipoles was represented by a Gaussian function. By minimizing the root mean square error between simulated and measured data, the precise position was determined. The benefit of using Setfos lies in its ability to precisely analyze and optimize complex optical and electrical properties of LECs, providing a deeper understanding of device physics and enabling performance improvements by confirming the desired central positioning of the p-n junction to suppress quenching effects.
Why it Matters
The use of exclusively metal-free TADF emitters in LECs provides a sustainable alternative to current LED and OLED technologies, which often rely on problematic metals and energy-intensive fabrication. LECs themselves can be manufactured cost-effectively and energy-efficiently using solution-based printing under ambient air.
The development of practical white LECs with competitive performance (high CRI, good EQE, angle-invariance) opens new avenues for illumination and flexible displays in various sectors, including healthcare, security, and communication.
This work represents the first demonstration of white emission from an LEC based solely on metal-free TADF compounds, marking a significant advancement in the field of organic electronics and paving the way for more sustainable and efficient light-emitting technologies.