Abstract
Siloxene and germanane are two-dimensional (2D) direct-bandgap semiconductors that hold promise for a range of applications, including photocatalysis, electronics, and photodetectors (PDs). In this study, we explore a novel direct Z-scheme 2D-2D siloxene/germanane heterojunction fabricated via wet-mixing self-assembly. This heterojunction exhibits superior light absorption compared with the individual nanosheets. Notably, when employed as a photoelectrode material for photoelectrochemical (PEC) PDs, it shows a marked photoresponse across the 365-980 nm range, with a peak responsivity at 520 nm. Specifically, under 520 nm illumination, its responsivity surpasses those of siloxene and germanane nanosheets by factors of 221.3 and 3.7, respectively. Remarkably, even at zero bias, it achieves a high photoresponsivity of 3.75 μA W-1 and a detectivity of 1.3 × 108 Jones, demonstrating excellent self-powered performance. Owing to its exceptional light sensitivity at 520 nm, the Z-scheme heterojunction is particularly well suited for the PEC photodetection of tartrazine, offering an ultralow detection limit of 0.3 pM and a broad linear range from 1 pM to 1 μM in aqueous media. Overall, this research highlights the considerable potential of the siloxene/germanane heterojunction for advanced optoelectronic applications, including high-performance PDs and PEC sensors.