TES-ADT三重項消滅剤における凝集による一重項生成の促進と光子アップコンバージョン

Triplet-triplet annihilation (TTA)-mediated photon upconversion (UC) offers a promising route for transforming low-energy photons into higher-energy ones under low-power, incoherent excitation, with applications in photovoltaics, bioimaging, 3D printing, etc. However, a central constraint on UC efficiency is the limited spin-statistical factor (f), which dictates the yield of singlet state formation and is especially challenging in the desirable far-red/NIR spectral range. Here, we explore a new approach of tuning the annihilator's f factor through controlled aggregation. The study covers a systematic investigation of triethylsilyl-substituted anthradithiophene (TES-ADT) annihilator solutions across a range of concentrations, complemented by studies on a neat TES-ADT film and density functional theory (DFT) calculations. We report a remarkable 3-fold enhancement in singlet yield, boosting the f value from ca. 20% to an impressive ca. 60% upon increasing annihilator concentration, which is shown to be directly linked to annihilator aggregation. DFT calculations further suggest that dimerization-induced shifts in energy levels and the accessibility of higher-energy triplet states (up to T₆) facilitate spin-conversion processes. Our findings unveil aggregation-enhanced singlet generation via TTA in TES-ADT, providing a valuable insight for designing more efficient UC systems by tailoring energy landscapes through molecular packing.