Significance Lead Sulfide colloidal quantum dots (PbS CQDs) and their nanocrystals have attracted researcher’s interest due to their unique physical properties, including broadly tunable bandgaps, exceptional absorption coefficients, and large exciton Bohr radii. These characteristics enable spectral response of PbS CQDs across the short-wave infrared range while demonstrating outstanding infrared photosensitivity, establishing them as highly promising materials for photodetection applications. In recent years, because of advancements in material fabrication techniques, researchers have successfully developed PbS-based optoelectronic devices exhibiting broad-band response characteristics spanning ultraviolet, visible and infrared regions. Owing to these superior properties, the optoelectronic devices have been applied in multiple critical fields including optical fiber communication systems, high-sensitivity imaging technologies, environmental sensing and monitoring, biomedical detection, as well as defense and so on.

Notably, PbS CQDs exhibit distinct size-dependent optical properties, with their absorption edges showing systematic redshift behavior as particle size increases. Through ligand optimized ligand engineering and material post-processing techniques, the key performance metrics of PbS CQDs-based photodetectors (such as responsivity and detectivity) can be significantly enhanced, while their physical and electrical characteristics undergo substantial modifications with material parameter variations. These research results demonstrate that strategies for improving PbS CQDs optoelectronic device performance should not only focus on optimizing the intrinsic photoelectric properties of quantum dots, more importantly, these advancements open new technological pathways for expanding their applications in infrared detection, next-generation solar cells, and high-performance photoelectric sensors.

Progress  The performance of PbS CQDs photodetectors is usually influenced by their morphology. PbS CQDs can be tailored to achieve small (1-10 nm) or large (10-100 nm) particle sizes, cubic structures, or spherical/other morphologies exceeding 100 nm. Studies indicate that adjusting sulfur sources, Pb precursors, Pb/S ratios, and quantum dots growth temperatures can modulate PbS CQDs into rod-like, cubic, or other shapes. Furthermore, the (111) and (100) crystal facets of PbS CQDs can be selectively suppressed or promoted, facilitating the synthesis of desired cubic or polyhedral morphologies.

　　Additionally, incorporating PbS into polymer matrices or employing nanowire/nanofilm structures can significantly improve light absorption and carrier collection efficiency in PbS photodetectors. Since photovoltaic devices fundamentally rely on the photovoltaic effect, their carrier density and concentration can be precisely tuned to configure them as either n-type or p-type.

　　PbS CQDs are typically capped with long-chain ligands to ensure colloidal stability, but short-chain ligands (small molecules, ions, lead halides, etc.) are often introduced via ligand exchange to enhance carrier transport. Different ligands adjust the dipole moment of PbS CQDs to different degrees to change its energy level. Heterojunction or gradient bandgap structures can be constructed through solid-phase or liquid-phase ligand exchange, which can combine the electronic properties of quantum dots with unique photoelectric characteristics to prepare photodetectors with low trap density and excellent device performance.

Conclusions and Prospects  In summary, the optoelectronic properties of PbS CQDs can be systematically engineered through multiple approaches. Morphology regulation is achieved by modulating growth temperatures to induce structural transitions from rod-like to cubic configurations, while precise adjustment of precursor ratios and chemical environments enables selective crystal facet manipulation. Composite architectures incorporating polymer matrices or low-dimensional nanostructures significantly enhance photon absorption and charge collection efficiency through optimized light-matter interactions. Doping strategies and heterojunction design provide flexible control over carrier type and concentration profiles. Surface chemistry optimization through rational ligand selection improves charge transport characteristics while passivating defect states. The synergistic integration of these quantum-confinement electronic properties with tailored device architectures enables the realization of high-performance photodetectors exhibiting both low trap-state densities and exceptional operational characteristics. These excellent capabilities establish PbS CQDs as a versatile materials platform for next-generation optoelectronic applications.