Ultrafast\nSpin Relaxation of Charge Carriers in Strongly\nQuantum Confined Methylammonium Lead Bromide Perovskite Magic-Sized\nClusters

Spin relaxation of charge carriers in strongly quantum\nconfined\nperovskite magic-sized clusters has been probed, for the first time,\nby using polarization-controlled femtosecond transient absorption\n(fs-TA) spectroscopy. Fs-TA measurements with a circularly polarized\npump and probe allowed for the determination of the exciton spin relaxation\nlifetime (∼1.5 ps) at room temperature based on the dynamics\nof a photoinduced absorption (PIA) feature peaked at 458 nm. This\nspin lifetime is shorter than that of perovskite quantum dots (PQDs)\nwith a larger size, and the results suggest that exciton confinement\nand defects likely play a more important role in these strongly quantum\nconfined magic-sized clusters with a larger surface-to-volume ratio.