Strong one-/two-photon excited fluorescence from long-range exciplex states in donor-spacer-acceptor system

The utilization of long-range coupled electron-hole pairs in exciplex-based thermally activated delayed fluorescence (TADF) materials exhibits charming potential in applications such as organic light-emitting diodes. In this work, we constructed a donor-spacer-acceptor (D-spacer-A) system with strong one-/two-photon excited fluorescence properties. This D-spacer-A system was constructed with 4,4′-cyclohexylidenebis[N,N-bis(p-tolyl)aniline] (TAPC) as the electron-donating molecule, 2,4,6-Tris(1,1′-biphenyl)-1,3,5-Triazine (T2T) as the electron-accepting molecule, and 1,3-Di-9-carbazolylbenzene (mCP) as the spacer molecule. By using a comprehensive analysis of photoluminescence (PL) spectra, PL transient decay curves, PL quantum yield values, and transient absorption measurements, the observed strong one-/two-photon excited fluorescence properties were attributed to the efficient utilization of long-range exciplex states. This work may be helpful for the understanding of long-range exciplex states in D-spacer-A exciplex TADF systems.