Achieving thermally enhanced upconversion emission via lattice distortion and dimer-mediated energy transfer in 0D Mn2+/Yb3+/Er3+-tridoped Cs3BiCl6 perovskites

Zero-dimensional (0D) halide perovskites inherently exhibit inefficient energy transfer for lanthanide-based upconversion luminescence (UCL) due to isolated structural units. Despite extensive research efforts, the exploration and validation of thermally enhanced UCL in 0D perovskites remain notably limited. This study demonstrates that Mn 2+ /Yb 3+ /Er 3+ tri-doping can achieve a ninefold enhancement of Er 3+ UCL in 0D Cs 3 BiCl 6 with preferential amplification of green emission. In particular, structural analysis, electron paramagnetic resonance, and steady-state spectroscopies confirm that the formation of Yb 3+ -Mn 2+ dimers can overcome the limitation of an ultralong interionic distance of 0.774 nm, enabling efficient energy transfer upconversion at elevated temperatures. Furthermore, comparative investigations with one-dimensional (Cs 3 Bi 2 Cl 9 ) and three-dimensional (Cs 2 NaBiCl 6 ) perovskites reveal that the pronounced UCL enhancement originates from Mn 2+ -induced lattice distortion and facilitates energy transfer from Yb 3+ -Mn 2+ dimer to Er 3+ . Finally, the optical thermometry exhibits a high absolute sensitivity of 2.09%/K and outstanding thermal cycling properties in the 313–573 K range, paving the way for optical sensing applications and beyond.