Converting Perovskite Nanocrystals to PbS Quantum Dots Toward Short-Wave Infrared Photodetectors

PbS quantum dots (QDs) are particularly promising in low-cost short-wave infrared (SWIR) photodetection and imaging applications. Herein, a novel method is introduced defined as the perovskite conversion method (PCM) fabricating PbS QDs by using perovskite nanocrystals (PeNCs) as the lead precursor. The elemental substitution mechanism for PbS QDs from PeNCs is proposed, and it is confirmed that PCM-QDs are exhibiting a smaller trap density due to a natural perovskite passivated surface condition compared to QDs prepared via conventional hot injection method (HIM). Grazing-incidence small-angle X-ray scattering (GISAXS) results indicate that a short-range disorder of the QDs can lead to a long-range disorder configuration in the inner structure of PCM-QD superlattice, which leads to a compact configuration in the QD solid film facilitating charge carrier transport in devices. In a photoconductor-typed SWIR photodetector (PD) comparison, PCM-QD PDs exhibit a high responsivity of 468 A W⁻¹ and detectivities of 2.1 × 10¹² Jones, which are almost three times higher than the values in HIM-QDs PDs. Moreover, PCM-QD PDs further show a higher response speed and one magnitude order higher loss frequency than PCM-QD PDs. PCM is promising in the fabrication of high-quality QDs for advanced optoelectronic applications.