Organic long-persistent-luminescent (OLPL) materials demonstrating hour-long photoluminescence have practical advantages in applications owing to their flexible design and easy processability. However, the energy absorbed in these materials is typically stored in an intermediate charge-separated state that is unstable when exposed to oxygen, thus preventing persistent luminescence in air unless oxygen penetration is suppressed through crystallization. Moreover, OLPL materials usually require ultraviolet excitation. Here we overcome such limitations and demonstrate amorphous OLPL systems that can be excited by radiation up to 600 nm and exhibit persistent luminescence in air. By adding cationic photoredox catalysts as electron-accepting dopants in a neutral electron-donor host, stable charge-separated states are generated by hole diffusion in these blends. Furthermore, the addition of hole-trapping molecules extends the photoluminescence lifetime. By using a p-type host less reactive to oxygen and tuning the donor–acceptor energy gap, our amorphous blends exhibit persistent luminescence stimulated by visible light even in air, expanding the applicability of OLPL materials.
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This work was supported by the Japan Science and Technology Agency (JST) FOREST project (grant number JPMJFR201H); JST ERATO, Adachi Molecular Exciton Engineering Project (grant number JPMJER1305); JSPS KAKENHI (grant numbers JP18H02049 and JP21H02020); JSPS Core-to-core project; the International Institute for Carbon Neutral Energy Research (WPI-I2CNER) sponsored by the Ministry of Education, Culture, Sports, Science, and Technology (MEXT), the OIST Proof of Concept (POC) Programme; and the Kyushu University Platform of Inter/Transdisciplinary Energy Research, young researcher/doctor student support programme. We thank K. Tokumaru for helpful discussions. We thank K. Kusuhara and N. Nakamura for their assistance with the preparation of TPBi, mCBP and TCTA.
The authors declare no competing interests.
Peer review information Nature Materials thanks Hugo Bronstein and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.
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Supplementary Figs. 1–14 and Table 1.
A melt casted TPP+/TPBi/TCTA sample was crashed and dispersed into water without nitrogen bubbling in NMR tube. Sample was photoexcited at 365 nm at room temperature.
LPL emission of TPP+/TPBi in air (top, left), TPP+/TPBi/TCTA in air (top, right), TPP+/TPBi in N2 (bottom, left) and TPP+/TPBi/TCTA in N2 (bottom, right).
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Jinnai, K., Kabe, R., Lin, Z. et al. Organic long-persistent luminescence stimulated by visible light in p-type systems based on organic photoredox catalyst dopants. Nat. Mater. 21, 338–344 (2022). https://doi.org/10.1038/s41563-021-01150-9
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