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PreprintCC BYChemRxiv

Donor–Acceptor Integration Modulates Reverse Intersystem Crossing in Multi-Resonant TADF Emitters

  • Pratiksha Dad1,2
  • Kittimeth Thammanatpong1,2
  • Mahni Fatahi3,4
  • Peter M W Gill1,2
  • Eli Zysman-Colman3,4
  • Girish Lakhwani1,2
4 affiliations
  1. 1School of Chemistry
  2. 2University of Sydney
  3. 3Organic Semiconductor Centre, EaStCHEM School of Chemistry
  4. 4University of St Andrews
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Abstract

Multi-resonant thermally activated delayed fluorescent (MR-TADF) compounds are attractive as emitters in organic light-emitting diodes (OLEDs) owing to their high photoluminescence quantum yields and narrowband emission. However, these emitters generally have moderate reverse intersystem crossing rate constants (kRISC), which causes triplet exciton accumulation and leads to, amongst other excitonic processes, triplet-triplet annihilation. This process results in significant efficiency roll-off in OLEDs at high luminance. Here, we report the photophysical properties of a 2 boron–nitrogen doped MR-TADF emitter, tCzBN, and two of its derivatives, SpAc-tCzBN and TRZ-SpAc-DBN, using time-resolved absorption and emission spectroscopy. Kinetic modelling of their photophysical behavior reveals that combining a donor–acceptor core with the MR-TADF moiety in TRZ-SpAc-DBN results in a higher kRISC than tCzBN and its donor-appended analog, SpAc-tCzBN, while preserving the narrowband emission of the MR-TADF unit. We attribute this enhancement to the lower effective adiabatic singlet–triplet energy gap (∆EST) and stronger spinorbit coupling in this molecular design.

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Cite

BibTeXRIS
BibTeX
@misc{dad2026donoracceptor,
  title = {{Donor–Acceptor Integration Modulates Reverse Intersystem Crossing in Multi-Resonant TADF Emitters}},
  author = {Pratiksha Dad and Kittimeth Thammanatpong and Mahni Fatahi and Peter M W Gill and Eli Zysman-Colman and Girish Lakhwani},
  howpublished = {ChemRxiv},
  year = {2026},
  month = oct,
  doi = {10.26434/chemrxiv.15009715/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009715/v1},
  note = {CC BY},
}
RIS
TY  - UNPB
TI  - Donor–Acceptor Integration Modulates Reverse Intersystem Crossing in Multi-Resonant TADF Emitters
AU  - Pratiksha Dad
AU  - Kittimeth Thammanatpong
AU  - Mahni Fatahi
AU  - Peter M W Gill
AU  - Eli Zysman-Colman
AU  - Girish Lakhwani
PY  - 2026
DA  - 2026/10/01
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15009715/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15009715/v1
AB  - Multi-resonant thermally activated delayed fluorescent (MR-TADF) compounds are attractive as emitters in organic light-emitting diodes (OLEDs) owing to their high photoluminescence quantum yields and narrowband emission. However, these emitters generally have moderate reverse intersystem crossing rate constants (kRISC), which causes triplet exciton accumulation and leads to, amongst other excitonic processes, triplet-triplet annihilation. This process results in significant efficiency roll-off in OLEDs at high luminance. Here, we report the photophysical properties of a 2 boron–nitrogen doped MR-TADF emitter, tCzBN, and two of its derivatives, SpAc-tCzBN and TRZ-SpAc-DBN, using time-resolved absorption and emission spectroscopy. Kinetic modelling of their photophysical behavior reveals that combining a donor–acceptor core with the MR-TADF moiety in TRZ-SpAc-DBN results in a higher kRISC than tCzBN and its donor-appended analog, SpAc-tCzBN, while preserving the narrowband emission of the MR-TADF unit. We attribute this enhancement to the lower effective adiabatic singlet–triplet energy gap (∆EST) and stronger spinorbit coupling in this molecular design.
ER  -