Heavy-atom-containing clusters, nanocrystals, and other semiconductors can sensitize the triplet states of their surface-bonded chromophores, but the energy loss, such as nonradiative deactivation, often prevents the synergistic light emission in their solid-state coassemblies. Cocrystallization allows new combinations of molecules with complementary properties for achieving functionalities not available in single components. Here, the cocrystal formation that employs platinum(II) acetylacetonate (Pt(acac)2 ) as a triplet sensitizer and electron-deficient 1,4,5,8-naphthalene diimides (NDIs) as organic phosphors is reported. The hybrid cocrystals exhibit room-temperature phosphorescence confined in the low-lying, long-lived triplet state of NDIs with photoluminescence (PL) quantum yield (ΦPL ) exceeding 25% and a phosphorescence lifetime (τPh ) of 156 µs. This remarkable PL property benefits from the noncovalent electronic and spin-orbital coupling between the constituents.
Keywords: cocrystallization; naphthalene diimide; phosphorescence; platinum complexes; triplet sensitization.
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