Dual-Mode Defect-Engineered MoS2/SnSe2 Heterostructures via Heavy Ion Irradiation for Solar-Blind UV Photodetection and Neuromorphic Optoelectronics

2D transition metal dichalcogenide (2D-TMDC) heterostructures hold transformative potential for optoelectronics, yet extending their spectral response to the solar-blind ultraviolet (SBUV, 200–280 nm) range while enabling neuromorphic functionalities remains challenging. A heavy ion irradiation-enabled defect engineering strategy is presented to achieve dual-mode optoelectronic operation in MoS₂/SnSe₂ heterostructures. Controlled irradiation simultaneously introduces latent track defects within channels and interfacial trap states. The engineered defects extend photoresponsivity to 200 nm (19.2 A W⁻¹), setting a new benchmark for SBUV detection in 2D materials, while interfacial states enable optoelectronic synaptic operations with short/long-term plasticity (STP/LTP) at 255 and 532 nm, demonstrating robust operation across wavelengths. Systematic characterization of paired-pulse facilitation (PPF) and long-term potentiation under repeated light stimuli confirms reproducible synaptic responses and enhanced state stability in irradiated devices. The engineered channel defects modify the band structure to facilitate SBUV photodetection, whereas the created interfacial trap states provide the necessary charge storage capability for neuromorphic computation. This work establishes heavy ion irradiation as a universal tool for multifunctional 2D optoelectronics, enabling concurrent SBUV photodetection and neuromorphic signal processing. The defect-mediated band/carrier engineering paradigm provides an atomic-scale blueprint for merging conventional optoelectronics with bio-inspired computing architectures.