Mn<sup>2+</sup>-Activated Zero-Dimensional Metal (Cd, Zn) Halide Hybrids with Near-Unity PLQY and Zero Thermal Quenching
Jumana Hasin Marayathungal, Deep Kumar Das, Rangarajan Bakthavatsalam, Jisvin Sam, Venkatesha R. Hathwar, Raghavaiah Pallepogu, Sudipta Dutta, Janardan Kundu
Abstract
Highly luminescent self-trapped exciton (STE)-based emission in low-dimensional antimony halide hybrids typically suffers from severe thermal quenching that limits their use in lighting applications. Interestingly, Mn 2+ -activated low-dimensional metal halide hybrids, with their characteristic d–d transitions, are less susceptible to thermal quenching. Consequently, developing Mn 2+ -activated metal halide hybrids with high PLQY and zero thermal quenching has received increasing research efforts. Herein, we synthesized Mn 2+ -doped zero-dimensional metal (Cd 2+, Zn 2+ ) bromide hybrids utilizing DABCO (1,4-diazabicyclo[2.2.2]octane) as the organic cation. Structural analysis confirms the presence of substitutional dopants (Mn 2+ ) in the host metal (Cd, Zn) halide hybrids. Optically, the Mn 2+ -doped Cd system (C 6 H 14 N 2 Cd 0.94 Mn 0.06 Br 4 H 2 O) shows (i) dual emission bands (green emission due to tetrahedral Mn center and orange emission due to host STEs), (ii) strong evidence of energy transfer from dopants to host (Mn → Cd), and (iii) zero thermal quenching behavior albeit with low PLQY. On the other hand, Mn 2+ -doped Zn hybrids (C 6 H 14 N 2 Zn 0.81 Mn 0.19 Br 4 ) demonstrate robust optical properties with highly luminescent (PLQY ∼ 94%) green emission (tetrahedral Mn center) and zero thermal quenching behavior. Such strongly luminescent zero thermal quenching behavior of Mn 2+ -activated metal halide hybrids could pave the way for the search for new functional materials for their use in high-temperature lighting applications.