Modulating TTA efficiency through control of high energy triplet states

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Materials for optical and electronic devices, 2022-03, Vol.1 (12), p.4923-4928
• Main Authors: Carrod, Andrew J, Cravcenco, Alexei, Ye, Chen, Börjesson, Karl
• Format: Article
• Language: English
• Subjects: absorption-spectra; annihilation; Chemistry; Configurations; limit; Materialkemi; Materials Chemistry; Materials Science; photon-up-conversion; Physics; Quantum efficiency; sensitization; singlet; Substitutes; Upconversion
• ISSN: 2050-7526; 2050-7534; 2050-7534
• DOI: 10.1039/d1tc05292f

An ideal annihilator in triplet-triplet annihilation photon upconversion (TTA-UC) can achieve a maximum of 50% quantum efficiency. This spin statistical limit depends on the energies of the triplet states of the annihilator molecule, with only 20% quantum efficiencies possible in less-optimal energy configurations ( E T 2 ≤ 2 E T 1 ). Our work utilises three perylene analogues substituted with phenyl in sequential positions. When substituted in the bay position the isomer displays drastically lowered upconversion yields, which can be explained by the system going from an ideal to less-ideal energy configuration. We further concluded position 2 is the best site when functionalising perylene without a wish to affect its photophysics, thus demonstrating how molecular design can influence upconversion quantum efficiencies by controlling the energetics of triplet states through substitution. This will in turn help in the design of molecules that maximise upconversion efficiencies for materials applications. It is shown here that positional isomerism of perylene substitution affects high energy triplet states differently. This in turn influences the quantum efficiency of triplet-triplet annihilation photon upconversion.