Achieving dual emission of thermally activated delayed fluorescence and ultralong room-temperature phosphorescence by controlling excited state dynamics through metal coordination

Abstract

Controlling excited-state dynamics is crucial for achieving dual emissions of ultralong room-temperature phosphorescence (URTP) and thermally activated delayed fluorescence (TADF), but remains challenging in the exploration of transition-metal compounds. Herein, we propose a new strategy to develop highly efficient TADF and URTP dual-emission materials by modulating URTP organic molecules through metal ion coordination. Specifically, Ag⁺ ions narrow the singlet-triplet energy gap (ΔE_ST) and enhance spin–orbit coupling (SOC), thereby accelerating intersystem crossing (ISC) and facilitating reverse intersystem crossing (RISC). The Ag⁺ ions also balance radiative transitions and RISC processes of the T₁ state. Consequently, coordinating the URTP molecule Phen-Tpa with Ag⁺ ions results in an Ag(I) complex that exhibits efficient ligand-centered TADF and URTP dual emissions in MeOBP films, with a quantum yield of 85%, an afterglow duration of 6 seconds, and a record long emission lifetime of 575.7 ms. Moreover, Phen-Tpa can be used to fabricate organic white light-emitting diodes (LEDs), while both Phen-Tpa and the Ag(I) complex offer high-security anti-counterfeiting capabilities. These results deepen the understanding of how metal fragment coordination influences luminescence mechanisms and provide a new approach for achieving dual emissions with coexisting TADF and URTP in transition-metal compounds.