Flexible Microcomb Printed PbS Quantum Dot Film Enables Scalable Fabrication of Near Infrared Photodetector

Colloidal PbS quantum dots (QDs) have attracted tremendous attention in near-infrared photodetection for their superior optoelectronic properties. However, appropriate fabrication methods remain a challenge for scalable and high performance PbS QD photodetectors. Herein, a flexible microcomb printing (FMCP) technique is first introduced to fabricate PbS QD photoconductors without a layer-by-layer ligand exchange technique, and the detectors demonstrate a responsivity of 2.1 A W-1. A computational fluid dynamics model is built to simulate the flow field distribution and analyze the relationship between the key parameters of FMCP and QD film morphology. The QD ink flow field at the tip of the microcomb exhibits high shear rates that lead to a better crystallization configuration for solid QD films formation, which is verified by Grazing-incidence small and wide-angle X-ray scattering. Moreover, the relationship between the intrinsic nature of the QD ink (viscosity and surface tension), substrate temperature, and printing speed are systematically analyzed to experimentally achieve high performance QD films. Benefiting from the good crystallization configuration, FMCP-printed photodetectors using the direct PbS QD ink without ligand exchange show high responsivities. The results indicate that FMCP is a promising method for scalable and high-performance PbS QD photodetectors.