Metal‐Free Benzothioxanthene Imide Based Dyes for Organic Light‐Emitting Electrochemical Cells

Abstract Two synthetic organic dyes of the Benzothioxanthene imide (BTI) family are explored as a promising electroactive material for organic light‐emitting electrochemical cells (LECs). The high thermal stability and ease of thin film processing make BTI‐based compounds suitable for these devices. However, their planar π‐conjugated structure often leads to aggregation‐caused quenching (ACQ), reducing luminescence in the solid state. To overcome this, this study has taken advantage of host‐guest interactions with 4,4′‐bis(9H‐carbazol‐9‐yl) biphenyl (p‐CBP), poly(9‐vinylcarbazole) (PVK), and poly(dioctylfluorene) (PFO) to suppress ACQ. The use of p‐CBP improved the internal electrical double layer (EDL) alignment within the film, resulting in higher luminescence compared to PFO and PVK‐based LECs. The BTI‐F dye, when incorporated into a dual host system with p‐CBP and PFO, achieved an impressive luminescence of up to 3900 cd m⁻². Additionally, PFO enhanced charge balance, contributing to a blue shift in maximum absorption wavelength and increasing the device's tolerance. A triple‐host system (p‐CBP, PVK, PFO) further extended the device's half‐life (t_1/2) to 54 min, demonstrating the potential of these host‐guest systems in advancing metal‐free LEC technology.