Achieving 1.0-s Thermally Activated Delayed Fluorescence via Synergistic Control of Reverse Intersystem Crossing and...

Area of Science:

• Organic electronics
• Photophysics
• Materials science

Background:

• Persistent thermally activated delayed fluorescence (p-TADF) is limited by kinetic trade-offs between reverse intersystem crossing (rISC) and triplet exciton decay.
• This trade-off restricts the achievable lifetime (τ_DF) of p-TADF materials.

Purpose of the Study:

• To overcome the lifetime limitations of p-TADF materials.
• To develop a synergistic strategy that slows rISC while promoting multiple intersystem crossing (ISC)/rISC cycles.

Main Methods:

• Investigated a synergistic strategy involving concurrent slowing of rISC rate (k_rISC) and promotion of multiple ISC/rISC cycles.
• Validated the approach using o-TFBCz, a novel p-TADF material.
• Performed quantitative photophysical analysis to determine exciton cycle dynamics.

Main Results:

• Achieved an unprecedented τ_DF of 1.00 s for o-TFBCz in unannealed poly(methyl methacrylate).
• Demonstrated an average of 2.1 ISC/rISC cycles per exciton, with k_ISC dominating over k_Fl and k_IC.
• Observed bluish-green afterglow and outstanding thermal stability.

Conclusions:

• Established a generalizable blueprint for breaking the lifetime ceiling of pure organic p-TADF materials.
• The synergistic strategy effectively enhances p-TADF material performance and stability.