High-performance PbS QDs/1T'-MoTe₂/ultra-thin SiO₂/Si heterojunction-based infrared broadband photodetectors

Zero-dimensional lead sulfide (PbS) quantum dots (QDs) with size-dependent bandgaps hold significant potential for efficient photodetection across a broad spectrum. However, the existence of a surface ligand on the surface of colloidal PbS QDs and the isolated state of the individual QDs deteriorate the performance of photodetectors (PDs). Here, a strategy is presented to realize high-performance photodetectors using PbS QDs without a surface ligand by transforming a PbI₂ film to PbS QDs using solid phase reaction on a 2D semimetallic 1T'-MoTe₂ layer. The PbS QDs/1T'-MoTe₂ heterojunction integrates the high broadband absorption of PbS QDs with the high conductivity of 1T'-MoTe₂, while the built-in electric field at the PbS QDs/1T'-MoTe₂ heterojunction interface further promotes efficient separation of photogenerated carriers. The PbS QDs/1T'-MoTe₂/ultra-thin SiO₂/Si PD can achieve pronounced photoresponse across a broad spectral range from 375 nm to 1550 nm. Under 375, 532, 808, 1342, and 1550 nm laser illumination, the responsivity values are 0.28 A W^-1, 0.52 A W^-1, 1.03 A W^-1, 0.07 A W^-1, and 0.042 A W^-1, respectively. Under 532 nm laser illumination, the PD exhibits a fast response time of 27.80/16.55 µs and a cutoff frequency of ∼20 kHz. Furthermore, the fabricated 4 × 4 PbS QDs/1T'-MoTe₂/ultra-thin SiO₂/Si PD array also achieves considerable pixel-to-pixel uniformity and broadband imaging capability. This work provides new possibilities for designing high-performance, broadband, and fast-response heterostructure PDs based on QDs, 2D materials, and Si.