Phenothiazine-Based Organic Phosphors with Dual-Site Oxidation: A Unified Platform for Triple-Mode Emission under Optical, Electrical, and X-ray Excitation

ABSTRACT Purely organic room-temperature phosphorescence (RTP) materials offer promising opportunities due to their metal-free composition, design flexibility, and ability to harness both singlet and triplet excitons. However, understanding their emission behaviors under diverse excitation modes remains limited. Here, we report a series of phenothiazine-based RTP luminogens with tunable sulfur oxidation states (–S–, –SO–, –SO₂–) and donor–acceptor architectures, enabling systematic control of electronic structures and molecular packing while preserving backbone consistency. These compounds provide a unified platform for multimodal luminescence, enabling stable phosphorescence emission under optical, electrical, and X-ray excitation. Notably, DOPTZ - SO₂ shows the highest RTP efficiency of 22.31% under photoluminescence excitation, while PTZ - SO₂ outperforms under electrical and X-ray excitation, showing over twice the external quantum efficiency in organic light-emitting diodes and a fivefold X-ray sensitivity enhancement. Comparative analyses across excitation conditions reveal distinct structure–property relationships. This work establishes a generalizable strategy combining oxidation-state modulation and excitation-mode adaptability for the development of efficient multimodal organic phosphors.