Infrared (IR) emission lead selenide (PbSe) quantum dots (QDs) have gained considerable attention in the last decade due to their potential applications in optoelectronic devices. However, the comprehensive applications of PbSe QDs have not been realized yet due to their high susceptibility to oxidation in air. In this paper, we demonstrate the stability enhancement of PbSe colloidal QDs via a post-synthetic ammonium chloride treatment and its applications in a solution-processed high-performance IR photodetector with a field-effect transistor (FET) configuration by reversely fabricating the PbSe active layer and polymethylmethacrylate (PMMA) dielectric layer. The responsivity and the specific detectivity of the FET-based photodetector Au(source, drain)/PbSe(52 nm)/PMMA(930 nm)/Au(gate) reached 64.17 mA W(-1) and 5.08 × 10(10) Jones, respectively, under 980 nm laser illumination with an intensity of 0.1 mW cm(-2). Therefore, it provides a promising way to make a high-sensitivity near-IR/mid-IR photodetector.