Estimation of the Rashba Strength from Second Harmonic Generation in 2D and 3D Hybrid Organic–Inorganic Perovskites

The Rashba effect (RE), caused by concurrent spin–orbit coupling and structural inversion asymmetry (SIA), has been invoked to explain outstanding optoelectronic properties of hybrid organic inorganic perovskites (HOIPs). The SIA in HOIPs also manifests itself in second harmonic generation (SHG). Here, we establish a quantitative relation between the RE strength and the low-frequency SHG value in two-dimensional (2D) and three-dimensional (3D) HOIPs using a newly developed effective-mass model. The calculated SHG, which exhibits one- and two-photon resonances between the valence and conduction bands, approaches a finite value at low frequencies. Using the measured SHG values in literature, the estimated RE strength is 10–3 eV Å for 3D CH3NH3PbI3 and 4 × 10–2 eV Å for 2D (C4H9NH3)2PbI4. Our results facilitate a simple and reliable determination of the RE strengths of 2D and 3D HOIPs and help quantify the impact of RE on various properties in HOIPs.