Weak magnetic field-dependent photoluminescence properties of lead bromide perovskites

The strong spin-orbit coupling (SOC) in lead halide perovskites, when inversion symmetry is lifted, has provided opportunities for investigating the Rashba effect in these systems. Moreover, the strong orbital moment, which, in turn, impacts the spin-pair in singlet and triplet electronic states, plays a significant role in enhancing the optoelectronic properties in the presence of external magnetic fields in lead halide perovskites. Here, we investigate the effect of weak magnetic fields (< 1 T) on the photoluminescence (PL) properties of CsPbBr3 nanocrystals with and without Ruddlesden-Popper (RP) faults and single crystals of CH3NH3 & nbsp;PbBr3. Along with an enhancement in the PL intensity as a function of an external magnetic field, which is observed in both lead bromide perovskites, the PL emission red-shifts in CsPbBr3 & nbsp;nanocrystals. Density-functional theory calculations of the electronic band-edge in CsPbBr3 & nbsp;show almost no change in the energy gap as a function of the external magnetic field. The experimental results, thus, suggest the role of mixing of the triplet and singlet excitonic states under weak magnetic fields. This is further deduced from an enhancement in PL lifetimes as a function of the field in CsPbBr3. In CH3NH3PbB3, an increase in PL intensity is observed under weak magnetic fields; however, no changes in the peak energy or PL lifetimes are observed. The internal magnetic fields due to SOC are characterized for all three samples and found to be the highest for CsPbBr3 & nbsp;nanocrystals with RP faults.& nbsp;Published under an exclusive license by AIP Publishing.