Yangtao Shao#, Xubin Wang#, Hexi Wei, Xinli Li, Rongrong Huang, Shiwei Yin, Haonan Peng*, Yu Fang*. J. Phys. Chem. Lett. 2026, DOI: 10.1021/acs.jpclett.6c00063

Previous works achieve TADF and RTP emission by regulating the aggregation state, molecular conformation or isomer engineering, and crystalline engineering^38-42. In many of these studies, the dual delayed emission is primarily enabled or switched by external packing/host/crystal factors, which can make it challenging to isolate a single intrinsic molecular parameter and establish a mechanistically attributable structure-spin-dynamics correlation. However, purely organic systems that can exhibit TADF/RTP dual delayed emission under ambient conditions remain relatively limited, and the underlying generalizable molecular design principles still require further exploration.

Here we implement carborane-number engineering in o-carborane functionalized triphenylamines (TPA-1Cb/2Cb/3Cb) to program the S₁-T_n landscape (S₁ = lowest singlet excited state; T_n = low-lying triplet states). Increasing the carborane count reshapes S₁-T_n alignments and facilitates intersystem crossing (ISC) and T_n-assisted reverse intersystem crossing (RISC), 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-T_n) 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.

Figure 1. (a) Reported design concepts for generating TADF or RTP in carborane-based emitters. (b) This work: carborane-number engineering that programs ΔE_ST and ISC/RISC to realize ultralong-lifetime TADF and tunable TADF/RTP dual emission. PF = prompt fluorescence; TADF = thermally activated delayed fluorescence; RTP = room-temperature phosphorescence.

Figure 2. (a) Solid-state PL (blue) and delayed PL (orange, gate = 25 ms) of TPA-1Cb/2Cb/3Cb (λ_ex = 360 nm). (b, c) Temperature-dependent steady-state PL of TPA-2Cb and TPA-3Cb powders. (d,e) Temperature-dependent transient PL decays monitored at 490 nm (TPA-2Cb) and 460 nm (TPA-3Cb). (f) TADF lifetimes of TPA-2Cb and TPA-3Cb vs temperature. (g, h) Energy-level diagrams and representative SOC values for TPA-1Cb and TPA-3Cb (TD-DFT, B3LYP/def2-SVP) in the solid state. (i) Proposed solid-state photophysical pathways (PF/TADF/RTP).

First Authors: Shao Yangtao and Wang Xubin, doctoral candidate, Shaanxi Normal University

Correspondence Authors: Prof. Fang Yu, Prof. Peng Haonan, Shaanxi Normal University

Full Text Link: https://pubs.acs.org/doi/10.1021/acs.jpclett.6c00063