Doped or not doped? Importance of the local structure of Mn (II) in Mn doped perovskite nanocrystals

Abstract Transition metal doping of semiconductor nanocrystals (NCs) can generate new optical, magnetic, properties through dopant-host interaction. Although Mn2+ doping in semiconducting NCs has been studied for decades, Mn doped perovskite NCs have opened up new avenues for optoelectronic applications due to signature Mn d-d emission. However, Mn doping in bromide-based perovskite NCs have not shown this signature peak sowing doubts about the efficient doping in these systems. Here, we demonstrate that the chemical bonding and local environment of Mn obtained using electron paramagnetic resonance (EPR) and X-ray absorption fine structure (XAFS) is similar to that of chloride-based perovskites. However, the differences in optical properties between the chloride and bromide-based perovskites NCs arises due to fundamental difference in mechanism in perovskite NCs compared to the II-VI semiconductor quantum dots. This provides some insight into this problem from a fundamental perspective leading to more efficient synthesis techniques for applications.