Studies on Annihilation and Coreactant Electrochemiluminescence of Thermally Activated Delayed Fluorescent Molecules in Organic Medium

Abstract

Very recently, there is a great research interest in electrochemiluminescence (ECL) featuring thermally activated delayed fluorescence (TADF) properties, i.e., TADF-ECL. It is appealing since the earlier reports in this topic well-confirmed that this strategy has a great potential in achieving all-exciton-harvesting ECL efficiency under electrochemical excitation, which is a breakthrough in the topic of organic ECL. However, organic phase electrochemistry and ECL studies surrounding TADF-ECL are still extremely rare. Especially, the ECL spectra of previous reported TADF emitters are still very different from their PL spectra. In this work, we systematically measure and discuss the liquid electrochemistry and ECL behavior of two typical TADF molecules in organic medium. Most importantly, we verify for the first time that the ECL spectra of them (coreactant ECL mode) are identical to their PL spectra counterparts, which confirms the effectiveness of TADF photophysical properties in the coreactant ECL mode in practice.

Materials for Electrochemiluminescence: TADF, Hydrogen‐Bonding, and Aggregation‐ and Crystallization‐Induced Emission Luminophores

“…The same group also studied the ECL behaviour of 4CzIPN and the TSCT emitter BPAPTC in dichloromethane. [17] In this work, the authors were able to demonstrate ECL emission under both annihilation and co-reactant pathways, with a maximum ECL efficiency of approximately two times relative to [Ru(bpy) 3 ] 2 + . When compared to the results provided by Ishimatsu, Adachi, Imato and co-workers who investigated the ECL of 4CzIPN in the annihilation pathway (λ ECL = 555 nm), a red-shifted emission at 600 nm was observed for the 4CzIPN-BPO co-reactant system.…”

“…Due to the TADF nature of PCzAPT10 , the ECL efficiency was enhanced fourfold compared to that of a fluorescent polymer standard F8BT, and two times to that of the [Ru(bpy) 3 ] 2+ /TPrA system. The same group also studied the ECL behaviour of 4CzIPN and the TSCT emitter BPAPTC in dichloromethane [17] . In this work, the authors were able to demonstrate ECL emission under both annihilation and co‐reactant pathways, with a maximum ECL efficiency of approximately two times relative to [Ru(bpy) 3 ] 2+ .…”

Thermally Activated Delayed Fluorescent Polymer Dots for Electrochemiluminescent Sensing of Cu2+ Ions

“…These T 1 states (ca. 75% in total) are capable of complete up-conversion into S 1 states under the assistance of environmental thermal energy via the efficient reverse ISC (RISC) process, followed by ECL via the delayed fluorescent (DF) route (DF-ECL). − Approximately 100% of Φ ECL can be realized in theory for the purely organic TADF-ECL system compared to ∼25% of Φ ECL for the conventional organic fluorescent (FL) ECL (FL-ECL) system. , The all-exciton-harvesting potential of TADF-ECL in organic media has been well documented, regardless of annihilation ECL or coreactant ECL. − Presently, the Φ ECL of TADF-ECL emitters using modified TADF molecules or polymers outperforms those of Ru­(bpy) 3 2+ and FL-ECL emitters. Furthermore, our group developed a few aqueous TADF-ECL biosensors.…”

Tailoring thermally activated delayed fluorescence emitters for efficient electrochemiluminescence with tripropylamine as coreactant

“…Despite the huge number of contributions concerning the use of TADF emitters in the various research areas listed above, only a limited number of recent studies have considered their application in electrochemiluminescence (ECL). [6][7][8] In our recent work on the topic we demonstrated that the ECL efficiency of para-monoimidazole benzonitrile derivatives is mainly dictated by the electrochemical reversibility of both cathodic and anodic processes rather than the photoluminescence quantum yields (PLQY). 9 In more detail, the screening of donor moieties showed that diphenylamine and tert-butyl carbazole derivatives are the most promising candidates, with ECL efficiencies one order of magnitude higher than the standard [Ru(bpy) 3 ]Cl 2 .…”

“…Despite the huge number of contributions concerning the use of TADF emitters in the various research areas listed above, only a limited number of recent studies have considered their application in electrochemiluminescence (ECL). 6–8…”