Unveiling Giant Injection/Shift Current Ratio in Hybrid Quasi-2D Perovskites

Abstract

The injection current induced by the bulk photovoltaic effect has garnered significant interest in the exploration of Rashba–Dresselhaus splitting in perovskite materials. However, the injection current is frequently veiled by coexisting shift current, thereby confusion arises in various current measurements. Herein, a wavelength-dependent terahertz (THz) emission spectroscopy is employed to resolve the ratio between injection and shift currents in a hybrid quasi-2D perovskite (PEA)₂(MA)_n-1Pb_nI_3n+1 (n = 3 and 4). Nearly orthogonal directions of injection and shift currents are observed by analyzing the azimuthal angle dependence of THz emission. Under 480 nm circularly polarized light excitation, a remarkable injection current proportion (≈61.5%) is observed, demonstrating conclusive evidence of spin-orbit coupling-induced band splitting, potentially attributed to a mixed Rashba–Dresselhaus effect. The wavelength-dependent THz emission results suggest that the value and direction of injection and shift currents are related to the band splitting at the excited wavelength. Furthermore, the injection and shift currents can be turned by elliptically polarized laser excitation, which can generate a THz wave with a maximum ellipticity of ≈0.403. This work unveils the injection and shift currents in quasi-2D perovskites both qualitatively and quantitatively, providing crucial insights into advancements in both nonlinear optics and optoelectronic applications.