Spin dynamics of electrons, holes, and excitons in lead-halide perovskite semiconductors

Bulk lead-based perovskite and their nanostructures are a promising platform for spintronics [1] due to their long spin lifetime due to the suppression of the dominant spin relaxation mechanisms [2,3,4]. Exciton spin polarization at cryogenic temperatures in bulk perovskite crystals with near-cubic (FA₀.₉Cs₀.₁PbI₂.₈Br₀.₂, FAPbBr₃) and orthorhombic (MAPbI₃, CsPbBr₃) symmetries has high degree of optical orientation up to 85%, indicating strong spin selectivity and efficient spin initialization under circularly polarized excitation [2,3,5]. Spatial confinement of excitons in CsPbI₃ nanocrystals leads to a regime in which spin properties are governed primarily by the electron–hole exchange interaction within excitons, providing enhanced control over spin dynamics.

At the same time, spatial confinement of both excitons and acoustic phonons in CsPbI₃ nanocrystals results in significant enhancement of exciton–phonon interaction. This makes it possible to observe confined acoustic phonon modes in Raman scattering spectra. The size dependence of the acoustic phonon energies, combined with comparison to theoretical models, enables reconstruction of the nanocrystal shape and size without the need for transmission electron microscopy [6].

Furthermore, in an external magnetic field, magneto-optical techniques provide a powerful optical tool to determine the g-factors of excitons, electrons, and holes, and to gain insight into the mechanisms of electron–hole interaction and hyperfine interaction with nuclei spins [4,7]. Measurements of g-factor anisotropy allow one to optically identify the presence of domain structures in the bulk MAPbI₃ crystals, associated with different orientations of the crystallographic axes. 

Overall, exciton–phonon interactions in both bulk and nanocrystalline perovskites play a key role in the spin dynamics of excitons. These results highlight the importance of composite excitations, involving coupled spin, excitonic, and phononic degrees of freedom, for understanding and controlling spin-related phenomena in lead-halide perovskites.

References

[1] Organic Inorganic Perovskites: Physical Properties and Applications. (eds. Z. V. Vardeny and M. C. Beard) (World Scientific,2022).

[2] N. E. Kopteva, et al., Highly-polarized emission provided by giant optical orientation of exciton spins in lead halide perovskite crystals, Advanced Science, 11, 2403691 (2024). 

[3] N. E. Kopteva, et al., Effect of crystal symmetry of lead halide perovskites on the optical orientation of excitons, Advanced Science, 12, 2416782 (2025). 

[4] E. Kirstein, et al., Mode locking of hole spin coherences in CsPb(Cl,Br)₃ perovskite nanocrystals, Nature Comm., 14, 699 (2023). 

[5] Kopteva, N. E.; et al., Optical orientation of excitons and charge carriers in methylammonium lead iodide perovskite single crystals in the orthorhombic phase. Phys. Rev. B, 111, 195201 (2025).

[6] C. Harkort, et al., Confined acoustic phonons in CsPbI₃ nanocrystals explored by resonant Raman scattering on excitons. NANO Letters 25, 12754 (2025).

[7] C. Harkort, et al., Spin-Flip Raman Scattering on Electrons and Holes in Two-Dimensional (PEA)₂PbI₄ Perovskites. Small 19, 2300988 (2023).