Excited states engineering maximizes singlet generation by triplet fusion in conjugated systems
Abstract
Photon upconverters are anti-Stokes emitters capable of generating photons with higher energy than those absorbed. This behavior can be achieved through different mechanisms, which are extensively studied for applications in imaging, anticounterfeiting, information encryption and most importantly, solar energy technologies. Among these mechanisms, photon upconversion based on sensitized triplet-triplet annihilation (sTTA-UC) is particularly attractive because it operates under low-intensity, incoherent light. In sTTA-UC, two optically dark triplet states of a conjugated annihilator fuse upon collision to populate a higher-energy fluorescent singlet, with the triplets initially generated via energy transfer from a lower-energy sensitizer. Here we introduce a general molecular-design strategy to maximize singlet generation through TTA. By selective substitution, we engineered a naphthalene-derived annihilator with an excited-state energy landscape that favors singlet formation, achieving yields up to 0.83. When combined with an appropriate triplet sensitizer, the system delivers stable UV-visible upconversion peaking at 390 nm, with an absolute upconversion yield of 0.19 and an activation excitation intensity threshold lower than 0.1 suns under non-coherent broadband excitation fully compatible with the requirements of solar-powered technologies.
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BibTeX
@misc{ronchi2026excited,
title = {{Excited states engineering maximizes singlet generation by triplet fusion in conjugated systems}},
author = {Alessandra Ronchi and Masashi Mamada and Michel Frigoli and Angelo Monguzzi},
howpublished = {HAL},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2605.01998},
eprint = {2605.01998},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05785404v1},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Excited states engineering maximizes singlet generation by triplet fusion in conjugated systems
AU - Alessandra Ronchi
AU - Masashi Mamada
AU - Michel Frigoli
AU - Angelo Monguzzi
PY - 2026
DA - 2026/10/08
PB - HAL
DO - 10.48550/arxiv.2605.01998
UR - https://hal.science/hal-05785404v1
AB - Photon upconverters are anti-Stokes emitters capable of generating photons with higher energy than those absorbed. This behavior can be achieved through different mechanisms, which are extensively studied for applications in imaging, anticounterfeiting, information encryption and most importantly, solar energy technologies. Among these mechanisms, photon upconversion based on sensitized triplet-triplet annihilation (sTTA-UC) is particularly attractive because it operates under low-intensity, incoherent light. In sTTA-UC, two optically dark triplet states of a conjugated annihilator fuse upon collision to populate a higher-energy fluorescent singlet, with the triplets initially generated via energy transfer from a lower-energy sensitizer. Here we introduce a general molecular-design strategy to maximize singlet generation through TTA. By selective substitution, we engineered a naphthalene-derived annihilator with an excited-state energy landscape that favors singlet formation, achieving yields up to 0.83. When combined with an appropriate triplet sensitizer, the system delivers stable UV-visible upconversion peaking at 390 nm, with an absolute upconversion yield of 0.19 and an activation excitation intensity threshold lower than 0.1 suns under non-coherent broadband excitation fully compatible with the requirements of solar-powered technologies.
ER -