The charge carrier transfer across the QD/graphene interface potential barrier is crucial for the operation of the detector and is known to be temperature-dependent. Following illumination, the separated charge carriers recombine by temperature-driven charge carrier transfer over the potential barrier. In fact, for phototransistors operating at low temperatures, blocking of the charge carrier transfer and loss of the detector's functionality has been observed in a recent study with CsPbI3 QD/graphene FETs at a temperature of 200 K and constant gate voltage, as fewer charge carriers are transferred from the QDs to the graphene. Temperature-dependent investigations on PbS QD/graphene FETs have not been reported to date, yet they are imperative for the development of QD-based multicolor detector developments. Here, we present a study on temperatureand gate voltage-dependent photoresponsivity of PbS QD/graphene FETs. As opposed to previous experiments with CsPbI3 QDs, the photoresponse at low temperatures exceeds the room temperature value and changes its sign. As such, our findings demonstrate the importance of QD/graphene FETs for potential implementation in multicolor photodetector arrays, when combined with MWIR detectors fabricated on the same substrate, and guide the detector optimization by revealing fundamental principles of the photoresponse phenomenona. Figure depicts a schematic of a PbS QD/graphene FET. Colloidal PbS QDs were nanoprinted on top of graphene FET (5 μm channel width, 50 μm channel length) fabricated on Si/SiO2 substrates. The native oleic acid ligands of the QDs have been exchanged with 1,2-ethanedithiol via post-nanoprinting solid-state ligand-exchange. In a top-view optical brightfield image (Figure ) of a hybrid PbS QD/graphene FET, Si/SiO2 substrate is seen as violet region, the Au electrodes appear yellow, and the PbS QD thin film after ligand exchange is green. The graphene stripe is covered by the QD thin film and not visible in the optical image. For operation, a small sourcedrain bias is applied between the electrodes. Light is absorbed in the QD thin film resulting in the formation of an electronhole pair and the subsequent accumulation of one charge carrier type in the film and the opposite type being transferred to the graphene transistor. The carrier separation at the interface results in a change of the electric field and a measurable change in the conductivity of the graphene layer. An additional bottomgate voltage is applied to optimize the responsivity magnitude. Figure shows a typical wavelength-resolved photoresponse which follows the absorption spectrum of PbS QD colloidal dis-persion (Figure ), confirming the integrity of QD transformation after the printing and drying process. A detector array, consisting of three pixels, was fabricated (optical image in Figure ): one pixel is discussed in the main text and denoted "Device A1", while the results for Devices A2 and A3 can be found in the Supplementary Information. All three pixels were fabricated utilizing the same QD ink. As mentioned above, higher photoresponsivity is expected with higher photoconductive gain. Longer trapping times can, for example, originate from charge carrier accumulation at the interface barrier or by trapping the carriers by QD trap states. The latter can be achieved by QD oxidation, resulting in QD surface trap states, therefore, the QD ink was exposed for an extended time to ambient conditions prior to nanoprinting. The QD layer thickness was kept constant within each pixel, but varied from pixel to pixel in the range of 170-230 nm, allowing the investigation of the QD layer thickness dependence on the temperature-and gate-voltage-dependent responsivity measurements.