Design strategies for red/near-infrared aggregation-induced emission luminogens (AIE-gens) with biological applications still face significant challenges as the conventional pi-conjugated extension requires complex synthesis routes and usually suffers from poor solubility. Herein, we propose a delicate strategy for red emission through AIE of small conjugated structures, hexaselenobenzene derivatives (6SeBA and 6SeBPI), with the assistance of the heavy atom effect from the substitution of selenium. The hexaselenobenzene core exhibits both the AIE effect and efficient triplet-state emission. Through molecular engineering, 6SeBA exhibits bright and stable red photoluminescence at 650 nm with a large Stokes shift, and 6SeBPI shows dual emission bands, further demonstrating the dynamical monitoring of cellular processes via multichannel imaging. In addition, 6SeBPI can generate a greater quantity of reactive oxygen species upon exposure to light, thereby conferring the potential for photodynamic immunotherapy. This strategy provides insights into the design of red AIE luminogens with shorter conjugated scales, paving the way for simultaneous imaging and therapy.