5 years ago

Large Reverse Saturable Absorption at the Sunlight Power Level Using the Ultralong Lifetime of Triplet Excitons

Large Reverse Saturable Absorption at the Sunlight Power Level Using the Ultralong Lifetime of Triplet Excitons
Martin Vacha, Shuzo Hirata
Large reverse saturable absorption (RSA) at the sunlight power level was observed from a host–guest amorphous material composed of d12-coronene as a guest and β-estradiol as a rigid amorphous host. The large highly symmetric two-dimensional (2D) aromatic structure of d12-coronene doped into the rigid host causes ultralong triplet lifetime as well as high triplet yield, serving efficient accumulation of the triplet excitons of d12-coronene under weak excitation light. The high absorption coefficient of the triplet state (σ34) compared with that of the ground state (σ01) for d12-coronene is also caused by the highly symmetric 2D aromatic structure. The efficient accumulation of the triplet excitons and high σ34 – σ01 led to an onset of the RSA characteristics under irradiance below 10–1 mW cm–2. A film of the amorphous material showed a large decrease of transmittance from 66% at 0.02 mW cm–2 to 24% at 50 mW cm–2 for continuous light at 405 nm.

Publisher URL: http://dx.doi.org/10.1021/acs.jpclett.7b01456

DOI: 10.1021/acs.jpclett.7b01456

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