AbstractThe research of purely organic room‐temperature phosphorescence (RTP) materials has drawn great attention for their wide potential applications. Besides single‐component and host–guest doping systems, the self‐doping with same molecule but different conformations in one state is also a possible way to construct RTP materials, regardless of its rare investigation. In this work, twenty‐four phenothiazine derivatives with two distinct molecular conformations were designed and their RTP behaviors in different states were systematically studied, with the aim to deeply understand the self‐doping effect on the corresponding RTP property. While the phenothiazine derivatives with quasi‐axial (ax) conformation presented better RTP performance in aggregated state, the quasi‐equatorial (eq) ones were better in isolated state. Accordingly, the much promoted RTP performance was achieved in the stimulated self‐doping state with ax‐conformer as host and eq‐one as guest, demonstrating the significant influence of self‐doping on RTP effect.