A supplemental solution to surface-passivate large-size PbSe quantum dots for high-performance photodetectors

As a promising material, lead selenide (PbSe) colloidal quantum dots (CQDs) are widely studied for its applications in the next generation photodetectors due to their solution-processability and low cost. However, the (100) surfaces PbSe QDs are usually passivated incompletely by the traditional liquid-phase ligand exchange with the halogen ligands when the diameter of PbSe QDs is larger than 5.0 nm. As compared to the traditional strategies of the halogen ligands, in this work methylammonium acetate (MAAc) was added as an additive into the PbI₂ ligand solution to form the perovskite intermediate (i.e. MAPbI_3-xAc_x) as the ligand attached onto the (100) face of PbSe, in this way, to enhance the surface passivation and the dispersion of PbSe CQDs. Therefore, the as-synthesized infrared photodetector ITO/ZnO/PbSe-MAPbI_3-xAc_x/Ag showed decreased dark current by more than five-fold, and thus its device performance is enhanced greatly. As a result, a high photoresponsivity of 0.32 mA/W with a specific detectivity of 1.16 × 10¹¹ Jones was obtained from the photodetector ITO/ZnO/PbSe-MAPbI_3-xAc_x/Ag under 47.8 µW/cm² 1550 nm illumination. Thus, it provides a supplemental solution to completely surface-passivate CQDs in large size for next generation optoelectronics.