Beyond Radical Emitters: Hot‐Exciton Electroluminescence From Singlet Diradicaloids
5 affiliations
- 1Istituto per lo Studio dei Materiali Nanostrutturati Consiglio Nazionale delle Ricerche Bologna Italy
- 2Dipartimento di Chimica “Giacomo Ciamcian” Università di Bologna Bologna Italy
- 3Dipartimenti di Chimica Università degli Studi di Bari Aldo Moro Bari Italy
- 4Department of Chemistry Biology and Biotechnology University of Perugia Perugia Italy
- 5Center for Chemical Catalysis—C3 and INSTM UdR Bologna Alma Mater Studiorum—Università di Bologna Bologna Italy
Abstract
Overcoming the 25% spin‐statistical limit of fluorescent emitters remains a central challenge in organic electroluminescence. Although radical emitters efficiently harvest doublet excitons in organic light‐emitting diodes, their optoelectronic performance can be affected by limited charge‐carrier mobility and efficiency roll‐off. Here we introduce trityl‐based singlet diradicaloids with small diradical character as a new class of open‐shell emitters and demonstrate their operation in organic light‐emitting transistors (OLETs) using the polychlorinated Thiele hydrocarbon (TTH) as emitter. Comparison with previously reported radical‐based devices reveals spin utilization around or exceeding 0.38 in TTH‐based OLETs. Time‐resolved electroluminescence, fs and ns transient absorption measurements, and quantum‐chemical calculations demonstrate that this enhancement does not originate from triplet–triplet annihilation but from hot‐exciton mechanism enabled by the diradical electronic structure, where the T2 state efficiently repopulates the emissive singlet via reverse intersystem crossing (RISC). Unlike conventional hot‐exciton emitters based on donor–acceptor architectures, this system demonstrates hot‐exciton behavior in a singlet diradicaloid framework. Reduced charge trapping further highlights singlet diradicaloids with small diradical character as promising platforms for efficient and stable electroluminescent devices.
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BibTeX
@article{prosa2026beyond,
title = {{Beyond Radical Emitters: Hot‐Exciton Electroluminescence From Singlet Diradicaloids}},
author = {Mario Prosa and Eugenio Lunedei and Michele Orza and Davide Mesto and Roberto Cantoni and Francesco Reginato and Angela Punzi and Arthur R. J. Barreto and Yasi Dai and Benedetta Carlotti and Fabrizia Negri and Stefano Toffanin and Davide Blasi},
journal = {Angewandte Chemie (International Ed. in English)},
year = {2026},
month = sep,
doi = {10.1002/anie.6379738},
url = {https://doi.org/10.1002/anie.6379738},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Beyond Radical Emitters: Hot‐Exciton Electroluminescence From Singlet Diradicaloids
AU - Mario Prosa
AU - Eugenio Lunedei
AU - Michele Orza
AU - Davide Mesto
AU - Roberto Cantoni
AU - Francesco Reginato
AU - Angela Punzi
AU - Arthur R. J. Barreto
AU - Yasi Dai
AU - Benedetta Carlotti
AU - Fabrizia Negri
AU - Stefano Toffanin
AU - Davide Blasi
PY - 2026
DA - 2026/09/22
JO - Angewandte Chemie (International Ed. in English)
DO - 10.1002/anie.6379738
UR - https://doi.org/10.1002/anie.6379738
AB - Overcoming the 25% spin‐statistical limit of fluorescent emitters remains a central challenge in organic electroluminescence. Although radical emitters efficiently harvest doublet excitons in organic light‐emitting diodes, their optoelectronic performance can be affected by limited charge‐carrier mobility and efficiency roll‐off. Here we introduce trityl‐based singlet diradicaloids with small diradical character as a new class of open‐shell emitters and demonstrate their operation in organic light‐emitting transistors (OLETs) using the polychlorinated Thiele hydrocarbon (TTH) as emitter. Comparison with previously reported radical‐based devices reveals spin utilization around or exceeding 0.38 in TTH‐based OLETs. Time‐resolved electroluminescence, fs and ns transient absorption measurements, and quantum‐chemical calculations demonstrate that this enhancement does not originate from triplet–triplet annihilation but from hot‐exciton mechanism enabled by the diradical electronic structure, where the T2 state efficiently repopulates the emissive singlet via reverse intersystem crossing (RISC). Unlike conventional hot‐exciton emitters based on donor–acceptor architectures, this system demonstrates hot‐exciton behavior in a singlet diradicaloid framework. Reduced charge trapping further highlights singlet diradicaloids with small diradical character as promising platforms for efficient and stable electroluminescent devices.
SN - 1433-7851
SN - 1521-3773
ER -