Spin coating: All spin coating was performed in a nitrogen-filled glovebox. PbS QD solutions in toluene (80 μL) were spin-coated at 1500 rpm for 30 seconds with a 0.8 second ramp (1,875 rpm/s ramp). TCA solutions in acetonitrile (100 μL) were spun on top of the PbS QD film with the same spin conditions. After the spin(s), the substrates were annealed on a hot plate at 70 °C for 15 minutes.