Lead sulfide (PbS) quantum dots (QDs) of different sizes are deposited with supercritical fluid CO₂ (sc-CO₂) to form laterally uniform PbS quantum dot films on glass substrates as compared to other deposition methods. Fluorescence and photoluminescence (PL) spectra of PbS QDs obtained from these closely packed films prepared by the sc-CO₂ method reveal effective Förster resonance energy transfer (FRET) between PbS QDs of two different sizes, while the films composed of three different sizes of PbS QDs show an even more effective FRET from the smallest to the largest particles. The FRET measured by PL is consistent with that measured by fluorescence spectroscopy at room temperature. From the PL studies of PbS QD films containing two different QD sizes, we demonstrate that the occurrence of FRET under cryogenic conditions is more efficient.