Mechanistic insights into tunable luminescence and persistent luminescence of the full-color-emitting BCNO phosphors

Boron carbon oxynitride (BCNO) phosphors can exhibit remarkable tunable emission colors and greenish persistent luminescence without the assistant of rare-earth ion dopants. However, the photoluminescent and persistent luminescence (PL) mechanisms of BCNO are still not fully understood. In this work, we attempt to reveal distinct photoluminescent and PL mechanism of BCNO based on the first-principles computation. Our results show that the tunable emission of BCNO stems from the carbon quantum dots (CQDs) embedded in the host BN lattice rather than originally expected from isolated carbon impurity. The embedded CQDs can emit light with size-dependent wavelength (color). Furthermore, oxygen ions chemisorbed at the edge of BCNO can passivate the dangling bonds, and thereby enhance BCNO's quantum efficiency. The PL mechanism can thus be attributed to the defect levels within the band gap, induced by CQDs. This mechanism is distinctly different from the conventional PL mechanism for the rare-earth-metal doped aluminate phosphors [Chem. Mater. 2015, 27, 2195-2202]. The obtained new insights into the luminescent and PL mechanisms of BCNO will not only benefit engineering novel optical materials with improved PL properties, but also promote future R&D efforts in exploiting broader application opportunities for the BCNO family phosphors.

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