Endothermic and Exothermic Energy Transfer Made Equally Eﬃcient for Triplet−Triplet Annihilation Upconversion
Research output: Contribution to journal › Article › Scientific › peer-review
|Pages (from-to)||318−324 |
|Journal||Journal of Physical Chemistry Letters|
|Early online date||2019|
|Publication status||Published - 2020|
|Publication type||A1 Journal article-refereed|
Expanding the anti-Stokes shift for triplet–triplet annihilation upconversion (TTA-UC) systems with high quantum yields without compromising power density thresholds (Ith) remains a critical challenge in photonics. Our studies reveal that such expansion is possible by using a highly endothermic TTA-UC pair with an enthalpy difference of +80 meV even in a polymer matrix 1000 times more viscous than toluene. Carrying out efficient endothermic triplet–triplet energy transfer (TET) requires suppression of the reverse annihilator-to-sensitizer TET, which was achieved by using sensitizers with high molar extinction coefficients and long triplet state lifetimes as well as optimized annihilator concentrations. Under these conditions, the sensitizer-to-annihilator forward TET becomes effectively entropy driven, yielding upconversion quantum yields comparable to those achieved with the exothermic TTA-UC pair but with larger anti-Stokes shifts and even lower Ith, a previously unattained achievement.