NIR/Visible Light Double Beam Synergistically Enhanced the Emission of Triplet‐Triplet Annihilation Upconversion via Thermal Lensing Effect

Abstract Stimuli‐responsive triplet‐triplet annihilation upcoversion (TTA‐UC) systems show additional application potentials in biological and environmental sensing besides the typical applications, such as improving the efficiency of solar‐powered devices. This work presents a double‐beam synergistically controlled TTA‐UC system that can increase the UC emission intensity by more than 6‐fold with the aid of the thermal lensing effect of an near‐infrared (NIR)‐absorbing solution in a double‐beam coupling system of visible/NIR light. The collimation effect of a divergent 532 nm laser beam, achieved through the concave lens effect of a Pdpc(OBu) 8 solution under NIR irradiation, significantly increases the excitation power density of the UC system, which is responsible for the increment of UC emission intensity. The ON/OFF ratio of the TTA‐UC switching can be conveniently regulated by the output power of either the 532 nm laser or 721 nm laser, as well as the concentration and compounds of the photothermal lens effect solution. The visible/NIR stimuli‐responsive TTA‐UC system is applied to photolithography to increase both the speed and depth of the photo printing.