Understanding Rashba Spin Splitting in Layered (BA)2PbX4 Perovskites: Implications for Optoelectronic Device Development*

Layered lead halide perovskites has attracted much attention as a promising material for a new generation of optoelectronic devices. Here, we perform a study on 2D layered (BA)₂PbX₄ by using different halide anions (X = I, Br, and Cl) along with quantum confinement. The obtained cell parameters evolution, supported by theoretical calculations, indicates strong lattice distortions of the metal halide octahedra breaking the local inversion symmetry in (BA)₂PbCl₄ which in turns strongly correlates with a pronounced Rashba spin splitting effect. Optical measurements reveal strong photoluminescence quenching and a drastic reduction in the PL quantum yield in this larger band gap compound. We suggest that these optical results are closely related to the appearance of the Rashba effect due to the exhistence of a local electric dipole. The results obtained in ab initio calculations showed that the (BA)₂PbCl₄ posses electrical polarization of 0.13 mC/cm² and spin-splitting energy of about 40 meV. Our work establishes that a local octahedra distortions induced Rashba spin splitting explains why obtaining UV-emitting materials with high PLQY is a big challenge.