Narrow bandgap colloidal quantum dots (CQDs), such as lead chacogenides, are promising materials in flexible electronics, light sensing and energy conversion. Among these nanomaterials, lead selenide (PbSe) CQDs have attracted emerging interest due to their potential applications in infrared (IR) optoelectronics, such as IR light-emitting diodes (LEDs), photodetectors and solar cells. Near-Infrared (NIR) photodetectors have applications in many fields such as communications and defence. [1] Solution-processed photodetectors are attractive for its low-cost fabrication but their performance so far has been limited. [2] for its poor film quality and its long-chain ligands.