Solution‐Phase Photon Upconversion With Sensitizer/4,4′‐Substituted 9,10‐Diphenylanthracene Mixtures

ABSTRACT Triplet–triplet annihilation upconversion (TTA‐UC) is a promising strategy for converting low‐energy photons into high‐energy photons. Among emitter molecules, 9,10‐diphenylanthracene ( DPA ) is widely used owing to its rigid aromatic structure, high fluorescence quantum yield (Φ FL ), and favorable triplet energy levels for efficient TTA‐UC. However, only a few systematic studies have examined how chemical substitutions at the 4‐positions of DPA affect their UC efficiency. Here, we investigate the effect of electron‐donating and electron‐accepting substituents at the 4‐positions of DPA on its fluorescence and TTA‐UC properties. DPA derivatives with substituents at the two 4‐positions of the phenyl rings were synthesized. The fluorescence properties of solutions of these DPA derivatives and the TTA‐UC properties of mixed solutions containing the DPA s and a sensitizer molecule were evaluated under a nitrogen atmosphere. The Φ FL of DCl‐DPA was the highest, followed by DCN‐DPA . The UC quantum efficiency ( η UC ) was estimated, with the highest value obtained for unsubstituted DPA , followed by DCl‐DPA and DCN‐DPA . Moreover, the saturated UC quantum efficiency ( η UC ∞ ), the quantum yield of triplet–triplet energy transfer, and the quantum yield of TTA (Φ TTA ) were also estimated. The results indicate that the Φ TTA value primarily governs the η UC ∞ values. These findings provide insight into the rational design of emitter molecules for optimizing TTA‐UC efficiency.