Controllable synthesis of wafer-scale two-dimensional PdTe2/PdSe2 vertical heterostructure with broadband nonlinear optical response

Two-dimensional (2D) materials have shown significant potential in electronics, optoelectronics, and nonlinear optics. However, individual 2D materials often face limitations in nonlinear optical (NLO) devices due to their narrow spectral responses and weak absorption. Herein, we report the wafer-scale synthesis of 2D PdTe2/PdSe2 vertical heterostructure using electron beam evaporation-assisted chemical vapor deposition. Open-aperture Z-scan measurements demonstrate exceptional nonlinear optical properties at 550, 1100, and 1550 nm. Notably, at 550 nm, the heterostructure exhibits a 48% higher nonlinear absorption coefficient, 58% deeper modulation depth, and 22% lower saturation intensity compared to pure PdTe2. At 1550 nm, the modulation depth reaches 31.92%, indicating a broadband response from visible to near-infrared spectrum. These improvements are attributed to interfacial charge transfer (CT) between PdTe2 and PdSe2, elucidating the synergistic effects of charge transfer and band engineering. This work provides critical experimental and theoretical insights for high-performance ultrafast photonic devices.