Ultrafast All‐Optical Logic Gates in Quasi‐2D Perovskites

Abstract Quasi‐2D perovskites are widely used in solar cells, photodetectors, and light‐emitting diodes (LEDs) due to their excellent optoelectronic properties and stability. However, much fewer all‐optical devices are realized based on quasi‐2D perovskites. Although perovskites have large nonlinear optical coefficients, the relaxation progress of excitons and carriers will slow down the response time and reduce the signal contrast of the all‐optical devices. In this paper, the exciton dynamics are investigated under off‐resonance excitation in quasi‐2D perovskite PEA₂(FAPbBr₃)₂PbBr₄. The spin‐selective optical Stark effect (OSE) is observed through circularly polarized transient absorption measurements, and a Stark shift of 3.3 meV is achieved under 1.11 eV excitation. The hot‐biexciton cooling process induced by two‐photon absorption is also observed. A spin‐based XNOR gate is demonstrated with a response time of ≈180 fs, and the logical signal contrast is enhanced through the competition of the OSE and the hot‐biexciton effect.