reversible electron injection by (spectro-) electrochemistry has been successfully demonstrated for almost all the QD examples listed above, hole injection is frequently more challenging. Potential reasons for this finding include the oxidation of the constituting anions and/or ligands of the QDs, leading to weak or often non-existing changes in the absorption spectra under oxidating electrochemical conditions. A potent strategy for detecting such small absorption changes is the application of a periodically modulating potential and tuning a lock-in amplifier onto the frequency of the modulation. With such potential-modulated absorption spectroscopy (EMAS), even weak signals can be distinguished from a prominent background. In this work, we apply H:In 2 O 3 (IHO) silica glass substrates as working electrodes (WE) for reductive and oxidative EMAS measurements of four different PbS QD samples with excitonic transitions between 1474 nm and 1729 nm. We demonstrate successful hole and electron injection and find evidence for shallow in-gap density of states.