PbS Quantum Dots Ink with Months‐Long Shelf‐Lifetime Enabling Scalable and Efficient Short‐Wavelength Infrared Photodetectors

Abstract The phase‐transfer ligand exchange of PbS quantum dots (QDs) has substantially simplified device fabrication giving hope for future industrial exploitation. However, this technique when applied to QDs of large size (>4 nm) gives rise to inks with poor colloidal stability, thus hindering the development of QDs photodetectors in short‐wavelength infrared range. Here, it is demonstrated that methylammonium lead iodide ligands can provide sufficient passivation of PbS QDs of size up to 6.7 nm, enabling inks with a minimum of ten‐week shelf‐life time, as proven by optical absorption and solution‐small angle X‐ray scattering. Furthermore, the maximum linear electron mobility of 4.7 × 10 −2 cm 2 V −1 s −1 is measured in field‐effect transistors fabricated with fresh inks, while transistors fabricated with the same solution after ten‐week storage retain 74% of the average starting electron mobility, demonstrating the outstanding quality both of the fresh and aged inks. Finally, photodetectors fabricated via blade‐coating exhibit 76% external quantum efficiency at 1300 nm and 1.8 × 10 12 Jones specific detectivity, values comparable with devices fabricated using ink with lower stability and wasteful methods such as spin‐coating.