Effect of Chirality on Carrier Spin Relaxation Dynamics in CsPbBr3 Perovskite Quantum Dots

Here, we investigate the temperature-dependent carrier spin relaxation dynamics of intrinsically chiral and ligand-induced chiral CsPbBr3 perovskite quantum dots (PQDs) using spin-selective femtosecond transient absorption (ss-TA) spectroscopy. Chirality was confirmed by circular dichroism (CD) measurements. In contrast to previously reported achiral CsPbBr3 PQDs, which exhibit a pronounced increase in spin relaxation lifetime from approximately 2 ps at room temperature to 57 ps at 77 K due to suppression of phonon-mediated Elliott–Yafet (EY) relaxation, all three chiral PQD systems display nearly temperature-independent spin relaxation over the same temperature range. Despite differences in particle size, ligand chemistry, photoluminescence quantum yield, and synthesis method, the three chiral systems exhibit similar dynamics, suggesting that broken mirror symmetry, rather than surface chemistry, governs the observed behavior, dominated by the D’yakonov–Perel (DP) mechanism. The results suggest that the combination of chiral symmetry breaking and strong spin–orbit coupling (SOC) leads to temperature-insensitive spin relaxation or DP mechanism, rather than the conventional EY mechanism dominated by electron–phonon coupling.