High performance NIR photodetector with mixed halogen passivation via precursor engineering

Atom passivation with halogen shows the best performance for PbS CQDs optoelectronic application for its short distance and stability via preventing oxidized to CQDs surface. Chlorine is hardly researched for its high activity and low binding energy to Pb. Here, lead halide was used as precursor by surface ligand engineering, introducing halogen during synthesis before ligand exchange and film deposition. Halogen of precursor was proved on the surface of as synthesized CQDs and still passivated on the surface after phase transfer ligand exchange by PbI2. Mixed halogen surface passivation layer balance the height and width of tunneling barrier between two adjacent CQDs which improving photo detector current and performance. Our works provide Cl doping passivation method but also elucidate understanding of the impact of photo detection performance via mixed halogen passivation.