An energetics assessment of benzo[a]tetracene and benzo[a]pyrene as triplet–triplet annihilation emitters

Abstract

Optical upconversion (UC) of low energy photons into high energy photons enables solar cells to harvest photons with energies below the band gap of the absorber, reducing the transmission loss....

Functionalized diketopyrrolopyrrole compounds for NIR-to-visible photon upconversion

“…S3 in the ESI †). As demonstrated previously, 14 higher f infers greater 2T 1 energy funnelling to the S 1 channel as compared to the losses to higher triplet states (e.g. T 2 state).…”

“…11,12 The key potential of TTA-UC lies in its ability to operate efficiently under sub-milliwatt incoherent excitation, which is found to be extremely attractive for a wide span of practical uses. Still, a few challenges such as lack of efficient TTA emitters, 13,14 particularly those upconverting NIR photons, and high sensitivity of the emitters to ambient conditions 15 remain, which limit TTA-UC application in practical devices. Generally, TTA-UC systems are composed of a sensitizer and an emitter/ annihilator pair.…”

The statistical probability factor in triplet mediated photon upconversion: a case study with perylene

“…are close enough to 2 Â T 1 , it may lead to enhanced non-radiative losses that will hinder the generation of emissive S 1 . Therefore, the DE 2T1-S1 and DE 2T1-T2 energy gaps have a strong influence on f, [27][28][29] which is discussed in this work.…”

Triplet–triplet annihilation mediated photon upconversion solar energy systems

“…The 2T 1 energy loss to T n was theoretically predicted to be the dominating non-radiative decay channel negatively affecting the 𝑓. 58,64 Recently, it was proven with diketopyrrolopyrrole (DPP) emitters that decreasing the energy gap between 2T 1 and T 2 was responsible for the decrease in 𝑓. 61 Hence it is essential to have a large energy gap between 2T1 and T n energy to have high 𝑓.…”

“…have been reported to exceed 1/5 36,49,62,63 as their energy state distribution is suitable for the TTA process (2T 1 4 S 1 ) and hinders other non-radiative decay channels such as singlet-fission (SF) or high energy triplet states (T n ). The 2T 1 energy loss to T n was theoretically predicted to be the dominating non-radiative decay channel negatively affecting the f. 58,64 Recently, it was proven with diketopyrrolopyrrole (DPP) emitters that decreasing the energy gap between 2T 1 and T 2 was responsible for the decrease in f. 61 Hence it is essential to have a large energy gap between 2T1 and T n energy to have high f. Considering the possible importance of f in annihilator design to achieve desired UC quantum yield, we have reviewed the reported f values of the widely used TTA annihilators over the UV-Vis spectral range to find possible trends or structureproperty relations (Fig. 6).…”