Dendri‐LEC Family: Establishing the Bright Future for Dendrimer Emitters in Traditional and Graphene‐Based Light‐Emitting Electrochemical Cells

Abstract

AbstractA rational implementation and optimization of thermally activated delayed fluorescent (TADF) dendrimer emitters in light‐emitting electrochemical cells (LECs) sets in the Dendri‐LEC family. They feature outstanding stabilities (90/1050 h for green/yellow devices) that are comparable to the best green/yellow Ir(III)‐complexes (450/500 h) and conjugated polymers (33/5500 h), while offering benefits of low‐cost synthesis and easy upscaling. In particular, a fundamental molecular design that capitalizes on exchanging peripheral substituents (tert‐butyl vs methoxy) to tune photophysical, electrochemical, morphological, and ion conductivity features in thin films is rationalized by temperature‐dependent steady‐state and time‐resolved emission spectroscopy, cyclic voltammetry, atomic force microscopy, and electrochemical impedance spectroscopy techniques. Herein, a TADF mechanism associated to a reduced photoluminescence quantum yield, but an enhanced electrochemical stability and ion conductivity enables to clarify the reduced device efficiency and brightness (4.0 lm W−1@110 cd m−2 vs 3.2 lm W−1@55 cd m−2) and increased stability (90 vs 1050 h) upon using methoxy groups. What is more, this substitution enables an excellent compatibility with biogenic electrolytes keeping device performances (1.9 lm W−1@35 cd m−2 and 1300 h), while graphene‐devices achieve on par figures to traditional indium–tin oxide‐devices. Overall, this work establishes the bright future of dendrimer emitters toward highly stable and truly sustainable lighting sources.