[1] Triplet-triplet annihilation was first discovered in the 1960s to explain the observation of delayed fluorescence in anthracene derivatives.
[9] The sensitizer absorbs the low energy photon and populates its first excited triplet state (T1) through intersystem crossing.
Both the emitter and sensitizer should have long triplet-state lifetimes so that the TTA mechanism has enough time to occur.
[9] In photolysis cancer therapy, light is used to selectively break bonds which releases and activates a target drug molecule.
The drug molecule can be released near or in tumour sites to combat the disease.
A
Jablonski diagram
describing the mechanism of triplet-triplet annihilation. The energy of the first triplet excited state (T
1
) is transferred to a second triplet excited state (T
1
), resulting in (1) the first T
1
returning to the singlet ground state S0 and (2) the second T
1
promoting to the singlet excited state (S
1
).
A Jablonski diagram describing the sensitization process in triplet-triplet annihilation upconversion. The sensitizer first absorbs light and reaches its first singlet excited state (S
1
). The sensitizer S
1
state undergoes intersystem crossing (ISC) to the triplet excited state (T
1
). The sensitizer then transfers energy to the emitter, which returns the sensitizer T
1
to the ground state (S
0
) and promotes the emitter to its T
1
.
