Organic Photothermal Materials Obtained Using Thermally Activated Delayed Fluorescence Design Principles

Abstract Organic small molecules with high photothermal conversion efficiencies that absorb near‐infrared light are desirable for photothermal therapy due to their improved biocompatibility compared to inorganic materials and their ability to absorb light in the biological transparency window (650–1350 nm). Here we report three donor‐acceptor organic materials DM‐ANDI , O‐ANDI , and S‐ANDI that show high photothermal conversion efficiencies of 46–68 % with near‐infrared absorption. The design of these molecules is based on the rational modification of a thermally activated delayed fluorescence material to favour a low photoluminescence quantum yield by reducing HOMO‐LUMO overlap. Encapsulating these materials into either neat nanoparticles or aggregated organic dots modulates their photothermal conversion efficiencies, and also facilitates dispersion in water.