Long-Lived Exciton Spin Coherence in Chiral Perovskite Colloidal Quantum Wells

Long-lived spin coherence is critical for spintronic and quantum technologies. Chirality-induced spin selectivity (CISS) effects offer a means to generate spin polarization, yet their behavior in confined colloidal systems remains unclear. Here, we investigate spin dynamics in chiral-ligand-functionalized CsPbBr3 colloidal quantum wells (CQWs) of varying thicknesses (2–5 monolayers). The spin lifetime increases markedly with well width, with a slow relaxation component reaching 210 ps at room temperature in 5-monolayer chiral CQWs─nearly 2 orders of magnitude longer than in pristine samples and a 3-fold enhancement over the best reported values in chiral perovskites. This enhanced coherence yields 5% circularly polarized emission and 43% spin current polarization in a spin-valve device. Theoretical modeling indicates that chiral ligands suppress spin-flip processes by spin–orbit coupling mixing cancellation, an effect amplified in thicker CQWs. These findings demonstrate that combining chiral ligand functionalization with wide-width engineering enables robust room-temperature spin coherence in perovskite nanomaterials.