Regioisomeric Engineering for Triplet Harvesting through Triplet–Triplet Annihilation
Abstract
Three regioisomeric donor–acceptor–donor luminophores, 1DBF, 2DBF, and 3DBF, based on phenanthrene-9,10-dicarbonitrile (PHCN) acceptor and dibenzofuran (DBF) units, are designed to investigate regioisomer-dependent triplet exciton harvesting. The three emitters exhibit strong blue fluorescence in solution, with photoluminescence quantum yields of 63–87%, and show delayed fluorescence (DF) in both solution and solid states. Low temperature time-gated measurements, large singlet–triplet energy gaps, and concentration-dependent studies collectively support DF from triplet–triplet annihilation (TTA) mechanism rather than thermally activated delayed fluorescence (TADF). Notably, the substitution pattern strongly influences the excited state dynamics and triplet harvesting efficiency. Among the three regioisomers, 2DBF exhibits the most efficient TTA-derived DF, owing to favorable donoracceptor electronic coupling and a balanced contribution of 3 LE and 3 CT states, whereas the weaker coupling in 1DBF favors predominantly 3 LE character, resulting in stronger phosphorescence and less efficient triplet harvesting through TTA. These results demonstrate that regioisomeric engineering can effectively modulate donor–acceptor electronic coupling and triplet state character, providing a useful molecular strategy for tuning the balance between DF and phosphorescence in organic emitters.
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BibTeX
@misc{dutta2026regioisomeric,
title = {{Regioisomeric Engineering for Triplet Harvesting through Triplet–Triplet Annihilation}},
author = {Madhusudan Dutta and Partha Hazra},
howpublished = {ChemRxiv},
year = {2026},
month = oct,
doi = {10.26434/chemrxiv.15010328/v1},
url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010328/v1},
note = {CC BY-NC-ND},
}
RIS
TY - UNPB
TI - Regioisomeric Engineering for Triplet Harvesting through Triplet–Triplet Annihilation
AU - Madhusudan Dutta
AU - Partha Hazra
PY - 2026
DA - 2026/10/13
PB - ChemRxiv
DO - 10.26434/chemrxiv.15010328/v1
UR - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010328/v1
AB - Three regioisomeric donor–acceptor–donor luminophores, 1DBF, 2DBF, and 3DBF, based on phenanthrene-9,10-dicarbonitrile (PHCN) acceptor and dibenzofuran (DBF) units, are designed to investigate regioisomer-dependent triplet exciton harvesting. The three emitters exhibit strong blue fluorescence in solution, with photoluminescence quantum yields of 63–87%, and show delayed fluorescence (DF) in both solution and solid states. Low temperature time-gated measurements, large singlet–triplet energy gaps, and concentration-dependent studies collectively support DF from triplet–triplet annihilation (TTA) mechanism rather than thermally activated delayed fluorescence (TADF). Notably, the substitution pattern strongly influences the excited state dynamics and triplet harvesting efficiency. Among the three regioisomers, 2DBF exhibits the most efficient TTA-derived DF, owing to favorable donoracceptor electronic coupling and a balanced contribution of 3 LE and 3 CT states, whereas the weaker coupling in 1DBF favors predominantly 3 LE character, resulting in stronger phosphorescence and less efficient triplet harvesting through TTA. These results demonstrate that regioisomeric engineering can effectively modulate donor–acceptor electronic coupling and triplet state character, providing a useful molecular strategy for tuning the balance between DF and phosphorescence in organic emitters.
ER -