The PbS QDs stock solution was washed with acetone once more (4x acetone, 8800 rcf for 2 mins) to create a pellet. In a nitrogen-filled glovebox, this weighed pellet was dissolved in anhydrous toluene to make the solutions with the desired concentrations (5, 10, 25, 50 mg/mL via serial dilution) and filtered through 0.2 μm PTFE membrane syringe filters (Titan3, 17mm, filter blue) before spin coating. In a nitrogenfilled glovebox, a 10 mM stock solution of TCA in anhydrous acetonitrile was prepared by heating the solution at ~70 °C overnight. After cooling, the resulting solution was filtered through Titan3, 17mm, filter blue 0.2 μm PTFE membrane syringe filters and diluted as needed (3 mM or 6 mM TCA in acetonitrile) before spin coating.