This work introduces a dual-wavelength pulsed laser ablation approach to precisely engineer ZnO@CdO core–shell structures, leading to enhanced charge transport and photoresponse compared to conventional single-wavelength methods. To create a zinc oxide (ZnO) core, a 355 nm Nd:YAG laser was used to ablate a zinc target, and a 532 nm Nd:YAG laser was used to create a cadmium oxide (CdO) shell. To examine the impact of core–shell growth on the structural, optical, and photoresponse properties, the ZnO, CdO, and ZnO@CdO core–shell were deposited at two distinct laser irradiation durations, 10 and 15 min. X-ray diffraction (XRD) confirmed the formation of polycrystalline structures, with hexagonal phases for ZnO and cubic phases for CdO. Transmission electron microscopy (TEM) images revealed spherical nanoparticles that increased in size with increasing laser exposure time. The grain sizes were determined to be around 12.5, 20.4, 52.3, and 78.6 nm for ZnO, CdO, ZnO@CdO (10 min), and ZnO@CdO (15 min), respectively. The optical band gaps were discovered to be 3.2, 2.2, 2.7, and 2.4 eV for the same films. The photodetector consists of ZnO:Al/ZnO@CdO/Si and is tested at 500 nm and 100 mW/cm2. Surprisingly, the device demonstrated increased responsivity, detection capacity, and quantum efficiency at a 1 V bias voltage during laser exposure. Two peaks appeared: the first represented zinc oxide at 390 nm, and the second represented cadmium oxide at 530 nm. Specifically, the detector that was created at 15 min, the ideal duration for the findings that were obtained, showed a responsivity of 36 mA/W and a D* value of 1.1 × 1017 Jones and an equivalent quality factor of 90%. Additionally, the detector showed a rise/fall period of around 0.56 and 0.89 s at 10 min and 0.34 and 0.74 s at 15 min. The core–shell morphology’s enhanced carrier transport routes and effective charge separation at the ZnO/CdO heterojunction are responsible for this notable performance increase. According to these findings, the ZnO@CdO core–shell system that was created has promise for a new class of visible light detectors.
