Roslyn Forecast
Roslyn Forecast (RMIT University, Australia)
20
In triplet-triplet annihilation (TTA) the molecular energy of two photons is pooled and emitted as fluorescence of a single photon of higher energy. TTA is a promising means of accessing solar irradiance below the silicon bandgap and surpassing the thermodynamic limit for single-junction solar cells. In addition, TTA allows the output light wavelength to be tailored to a specific application via choice of molecule and functionalisation. As TTA is a spin-selective process it exhibits a magnetic field response, which has traditionally been described and modelled in the context of Atkins & Evans’ Theory.1 Here, we revisit the theory, motivating the origin of key equations and evaluating the assumptions behind them. We rederive the theory, which captures the typical situation for TTA in solution. We compute the relative contributions of all spin channels,2 not only the singlet as in the original, but also triplet and quintet channels. These new conditions change the evolution of decoherence in the system, and thus the final magnetic field response equations. The ramifications of these updates are discussed in light of recent magneto-photoluminescence experimental results.3,4 $^1$ Atkins P, Evans G. M*ol. Phys.* **1975**, 29, 921–935. $^2$ Forecast R, Campaioli F, Cole JH. *J. Chem. Theory Comput* **2023**, 19, 7816–7824. $^3$ Gholizadeh EM, Prasad SKK, Teh ZL, Ishwara T, Norman S, Petty AJ, Cole JH, Cheong S, Tilley RD, Anthony JE, Huang S, Schmidt TW. *Nat. Photonics* **2020**, 14, 585–590. $^4$ Forecast R, Campaioli F, Schmidt TW, Cole JH. *J. Phys. Chem. A* **2023**, 127, 1794–1800.