The sample preparation and assembly of the spectroelectrochemical measurement cell were conducted inside a nitrogen filled glovebox. Before film preparation, the IHO substrates were cleaned by sonication in acetone and hexane for 15 min each and rinsing with isopropanol. A treatment with (3-aminopropyl)trimethoxysilane (APTMS) was performed by placing the substrates in a stirred 3% APTMS toluene solution at 50 °C for 90 min followed by rinsing with toluene. For the sample preparation of PbS-A, 500 µL of a 2 µM PbS solution in n-hexane was dropped on the conductive side of a slightly tilted IHO substrate. After evaporation of the solvent, the substrate with the now formed PbS film was dipped into a solution of 3 % 1,2-Ethanedithiol (EDT) in MeCN for 30 s and then rinsed with MeCN. The samples of PbS-B, PbS-C and PbS-D were prepared by dropping 100 µL of the respective 1.5 µM PbS solution in toluene onto the APTMS-coated IHO substrate and spincoating for 30 s at 10 rps with a 3 s ramp. Afterwards, the sample was dried at 50°C followed by spincoating 200 µL of a 3% EDT/MeCN solution onto the substrate and washing with MeCN. These steps were repeated until a homogenous, transparent yet clearly visible film is gained. To ensure good contacting, the upper 25% of all IHO substrates was left uncoated.