White Emissions Containing Room Temperature Phosphorescence from Different Excited States of a D-π-A Molecule Depending on the Aggregate States.

Abstract

Development of pure organic molecular materials with room temperature phosphorescence (RTP) and their applications for white emitters have received significant attentions recently. Herein, a D–π–A molecule (DMACPPY) which can realize white emitting under ambient conditions both in the crystal state and the doped‐film state by combining RTP with two fluorescent emissions is reported. The white emission from the crystalline sample of DMACPPY consists fluorescence from S2 (the second excited singlet state) and S1 (the first excited singlet state) along with RTP from T1 (the first excited triplet state), namely, SST‐type white light. While, the white emission from the poly methyl methacrylate (PMMA) film doped with DMACPPY contains fluorescences from S2 and S1, and RTP from T2 (the second excited triplet state) rather than T1 (STS type). DMACPPY cannot exhibit white spectrum within alternative crystalline state since inferior RTP intensity despite similar ternary emissions. The results demonstrate that the emissive properties for excited states of DMACPPY can be tuned by changing the aggregate state from crystalline to dispersion state in PMMA film. This new RTP emitter fulfills the talent for white emitting and achieves dual‐mode white emissions, invisibly, expands the application range for pure organic and heavy atom‐free RTP materials.