The role of spin-lattice relaxation in magnetic field effects on the luminescence of amorphous and polycrystalline rubrene films

Wide Field Magnetic Luminescence Imaging

“…The similarity of these results is despite Tarasov et al using much thicker films than those used here and confirms the independence of singlet fission dynamics upon film thickness. [43] The MPL measurement for polycrystalline rubrene also showed a large decrease in photoluminescence (−11.6%) at low magnetic field followed by a monotonic increase approaching 0% MPL at high magnetic field (Figure 3), again, in good agreement with similar measurements by Tarasov et al [48] In preparation for MPL imaging, Hall sensor imaging of the magnetic field above the permanent magnets was undertaken (Figure 4), which, for the pair of cubic magnets with their poles oriented in-plane (Figure 4b,d), showed a bipolar field profile with a measured peak field of ±247 mT. The ring-shaped magnet, with its poles oriented out-of-plane, showed an asymmetrical field intensity with a peak field of +299 mT.…”

“…A reverse measurement was also performed for polycrystalline tetracene but no significant difference in the profile was observed suggesting that photo-oxidation in tetracene is negligible over the timescale of the measurement. The amorphous rubrene MPL measurements in Figure 3 agree with those of Tarasov et al [48] performed in a vacuum. The similarity of these results is despite Tarasov et al using much thicker films than those used here and confirms the independence of singlet fission dynamics upon film thickness.…”

“…The brightest regions show a maximum MPL of 9.3%, which correspond to µ 0 H = 247 mT, which was the peak field as measured by the Hall array sensor (Figure 4d). Identical behavior was observed with the amorphous rubrene images (Figure 5f [48] All measurements were performed under standard ambient temperature and pressure conditions. 247 mT from the amorphous rubrene MPL characteristic (Figure 3).…”

“…[30,35,48,49] These were thermally evaporated (base pressure ≈5 × 10 −5 Pa) onto Si (001) and quartz substrates (lateral dimensions ≈40 × 40 mm 2 ) at a rate of 1.5 nm s −1…”

Structure and dynamics of triplet-exciton pairs generated from singlet fission studied via magnetic field effects

“…However, this characterization is a difficult task, because the relevant processes-diffusion of a triplet exciton, triple fusion, and the spin dynamics of TP-are complicated. Covalently linked dimers in which triplet excitons are fixed have recently been employed to clarify the structure-function relationship in singlet fission [28][29][30][31][32][33][34][35][36] . However, details of the structure and diffusion pathways of TPs are still unclear.…”