Clarification of Mn2+ Doping of CH3NH3PbBr3 Perovskite Magic-Sized Clusters

Abstract

Mn²⁺ doping of CsPbBr₃ perovskite magic-sized clusters (PMSCs) has been reported previously, where PMSCs with first excitonic absorption and photoluminescence (PL) around 425 nm were reported originally, followed by Mn²⁺-doped PMSCs with host absorption and PL around 400 nm. There, the observed 25 nm blueshift was attributed to smaller PMSCs or the Cl⁻ ions introduced by MnCl₂ as dopant precursor. However, subsequent studies suggest that the 400 nm band may instead be due to ligand-assisted metal halide molecular clusters (MHMCs), which lack the A component of perovskite. This raises the question whether the originally claimed Mn²⁺-doped PMSCs are actually MHMCs. To unambiguously address this issue, Mn²⁺-doped CH₃NH₃PbBr₃ PMSCs were synthesized with PL at both 440 nm, attributed to the PMSC, and at 600 nm, attributed to Mn²⁺. Blueshifting of the host absorption and PL bands due to Cl⁻ codoping is avoided by selecting MnBr₂ as dopant precursor rather than MnCl₂. Dopant incorporation into PMSCs is further supported by PL excitation, time-resolved PL, and electron paramagnetic resonance studies. This work provides direct and strong evidence of successful Mn²⁺ doping in PMSCs.