Perovskite chiral multiple quantum wells with extended spin lifetime via efficient spin cascade

The promises of halide perovskites for chiroptical and spintronic applications hinge largely on how long their spin coherence can last. Recent demonstrations of spin injection from chiral single quantum wells to achiral semiconductors have enabled a variety of spin functionalities. However, their spin polarization at the device level remains limited due to rapid interfacial and bulk spin losses. Here we demonstrate a spin cascade strategy by constructing oriented perovskite chiral multiple quantum wells to extend the spin lifetime. In chiral multiple quantum wells, quantum wells with varying well widths exhibit intrinsic and continuous chirality across all quantum-well phases with an average circular dichroism dissymmetry factor of 1.5 × 10 −2 . In this system, slowly energy-varying and spatially coupled chiral multiple quantum wells establish consecutive intermediate polarization states for spin cascade, thereby extending the spin coherence lifetime to ~5 ns at room temperature. The long-lived spin coherence yields circularly polarized luminescence with a luminescence dissymmetry factor (| g lum |) of 1.4 × 10 −2 and spin-dependent charge transport with a polarization degree of over 80%, enabling efficient X-ray-triggered dissymmetric photopolymerization and high-performance circularly polarized light photodetectors. This work opens the way to long-lived spin coherence in halide perovskites, promoting their use in chiroptical and spintronic devices.