Phase-Coupled Charge Transport in MoS₂ Homostructures for Ultrabroadband UV–THz Photodetection

Achieving ultrabroadband photodetection with a single two-dimensional semiconductor remains challenging, as most transition metal dichalcogenide (TMD) devices operate only in the visible–NIR range and require complex heterostructures or chemical treatments. Here, we present a scalable MoS₂ homostructure composed of monolayer 1H, bilayer 2H, and metallic 1T′ domains integrated within a continuous film. The 1T′ phase is selectively induced through a plasma-driven diffusion reaction, forming in-plane phase junctions that create built-in fields and promote efficient broadband charge transport. This mixed-phase architecture enables detection across an exceptionally wide spectral range, from UV to THz (360 nm to 1 mm). The device operates self-powered in the UV–NIR region, exhibiting high voltage responsivities─∼2680 V/W at 532 nm and ∼1713 V/W at 633 nm─and rapid response times of ∼19–32 μs, all without external bias. A small applied voltage further extends the photoresponse into the THz regime. The large voltage output supports direct signal readout, reducing system complexity and power consumption. These results demonstrate that in-plane phase coupling in MoS₂ provides a simple and scalable route to single-material ultrabroadband photodetectors, enabling versatile operation across continuous-wave and pulsed illumination conditions.