Ternary Cocrystal with Long‐Lived Charge‐Transfer State for Efficient Light Conversion Applications

Abstract Charge‐transfer (CT) cocrystals have attracted continuous interest for their promising optical and optoelectronic applications. To improve the performance of this class of material, a CT cocrystal with long‐lived CT excitons is highly desired. Herein, the development of a pyrene‐doped trans ‐1,2‐diphenylethylene‐1,2,4,5‐tetracyanobenzene ternary cocrystal (named P‐T S ‐T C ) is reported. Compared to the undoped binary cocrystals (without pyrene), P‐T S ‐T C exhibits a two times longer CT exciton lifetime (≈60.2 ns), and thus 8.8‐ and 16.6‐times improvement in photocurrent response and photocatalytic H 2 evolution activity. By using transient photoluminescence spectroscopy, it is uncovered that the absorbed photon energy in P‐T S ‐T C is localized to a lower energy CT state through an efficient energy transfer process (≈389.8 ps) between two co‐existing CT states. The CT exciton lifetime is prolonged due to the weakened CT coupling strength, as a result of the enlarged donor‐acceptor distance and the change of geometric structure. The result is expected to inspire the design of cocrystals with manipulatable CT exciton properties and to promote the potential application of multi‐component CT cocrystals.