Electrochemically induced hyperfluorescence based on the formation of charge-transfer excimers

TL;DR

This paper introduces electrochemically induced hyperfluorescence (ECiHF) to significantly enhance the luminance, efficiency, and lifespan of electrochemiluminescent devices, enabling practical lighting and display applications.

Contribution

The study demonstrates a novel ECiHF mechanism using charge-transfer excimers to improve ECLD performance, surpassing previous brightness and longevity records.

Findings

Achieved luminance >6,200 cd/m2 in ECLDs

Operational lifetime increased over 10-fold

Energy level alignment is critical for efficiency

Abstract

Used extensively in sensing applications, the application of solution-state electrochemiluminescent devices (ECLDs) in lighting and displays has been constrained by their low luminance and short operational lifetime. Here, we report a record improvement in the luminance, efficiency, and operational longevity of ECLDs by introducing electrochemically induced hyperfluorescence (ECiHF) and demonstrate its use in a calligraphic display. We use the double-decker arrangement assumed by the electron donor and acceptor segments of the molecule TpAT-tFFO to realize thermally activated delayed fluorescence from an electrogenerated charge-transfer (CT) excimer state and a subsequent energy transfer to the rubrene emitter TBRb. ECLDs based on this strategy achieve an unprecedented luminance of >6,200 cd/m2 and their operational lifetime is more than 10-fold longer than all previous ECLDs with meaningful efficiency or brightness. We identify energy level alignment between excimer and emitter as a crucial factor for efficient ECiHF; spectroelectrochemical analysis reveals that devices with energy gaps < 0.4 eV operate on a pure excimer mechanism across a wide range of frequencies. Our findings highlight the potential of ECiHF for improving ECLDs and pave the way to commercial applications of this form of fluid light.