Programming the Excited-State Landscape Via Carborane Count for Dual TADF/RTP.

Concurrent thermally activated delayed fluorescence (TADF) and room-temperature phosphorescence (RTP) within one molecular family remain rare. Here we implement carborane-number engineering in o-carborane-functionalized triphenylamines (TPA-1Cb/2Cb/3Cb) to program the S1-Tn landscape (S1 = lowest singlet excited state; Tn = low-lying triplet states). Increasing the carborane count reshapes S1-Tn alignments and facilitates intersystem crossing and Tn-assisted reverse intersystem crossing, while aggregate confinement suppresses nonradiative decay, enabling dual-channel emission. Spectroscopy and transient absorption establish solution-phase TADF for TPA-2Cb/3Cb and solid-state, air-robust TADF/RTP coexistence under ambient atmosphere with ultralong TADF lifetimes of 67.4 ms (TPA-2Cb) and 105.3 ms (TPA-3Cb). TD-DFT based on crystal structures attributes channel allocation to carborane-count-dependent tuning of ΔE(S1-Tn) and finite spin-orbit coupling (SOC), whereas TPA-1Cb remains RTP-dominant due to large S1-T1/T2 separations. These results define a compact route to time-programmable, dual emission and offer a generalizable design principle for building concurrent TADF/RTP in carborane-based luminophores.