Many-Body Description of Excitons in a Chiral Perovskite [R/S-NEA]₂PbBr₄

Designing chiral perovskites for spintronic applications that leverage the chiral-induced spin selectivity (CISS) effect requires a deep understanding of their excited-state properties. Yet, the origin of the CISS effect in 2D PbBr₄-based chiral perovskites is poorly understood. While CISS is an inherently nonequilibrium process, we show that helpful insights can be gained from the chiral proximity effect, its equilibrium counterpart, where the chirality of the organic molecule is transferred to the achiral inorganic perovskite [1]. Since excitons are a valuable fingerprints of various proximity effects [2,3], it is important to establish their accurate description. We present a Green function based first-principles study of excitonic in [R/S-NEA]₂PbBr₄ using a quasiparticle self-consistent framework (QSGW) and the Bethe-Salpeter equation (BSE). Our calculations suggest an excitonic binding energy of 860 meV and provide a detailed real-space anatomy of the excitons, revealing Wannier-Mott type character with significant intersite transitions [1].

[1] Y. Liu et al.,  Adv. Funct. Mater. 2025, e09127 (2025)

[2] I. Zutic et al., Mater. Today 22, 85 (2019)

[3] B. Scharf et al., Phys. Rev. Lett. 119, 127403 ( 2017)