Broadband Nonlinear Photoresponse and Ultrafast Carrier Dynamics of 2D PdSe₂

Palladium diselenide (PdSe₂) exhibits considerable potential for application in broadband optoelectronic devices. In this work, the broadband nonlinear optical performance and ultrafast carrier dynamics from ultraviolet to near-infrared of a trilayer PdSe₂ are systematically studied. PdSe₂ is found to achieve a giant saturable absorption performance. The modulation depth is 22.47% at 520 nm, whereas the nonsaturable loss and saturation intensity are only 3.83% and 15.47 GW cm⁻², respectively, which are better than those of many 2D semiconductors. Based on these findings, a PdSe₂-based visible light thresholder is proposed, its function is to extract an undetectable pulse signal drowned in strong stochastic noise and thereby improve the signal-to-noise ratio. Pump–probe technique, along with first-principles calculation and transient absorption spectra, reveals the intrinsic recombination mechanism, including Auger scattering and trap saturation. This work is expected to establish the foundation for the development of next-generation PdSe₂-based devices in optoelectronics and visible light communication.