Thin-layer Bidim-SEC experiments were performed in custom-made cell designed for screen-printed electrodes (SPEs) described and tested previously. In order to perform studies in parallel configuration, two bare optical fibres (100 μm in diameter, Ocean Optics) were attached to a quartz plate using nail polish. The first optical fibre was connected to the light source, and the Bidim-SEC experiments were carried out using two customised SPELEC instruments (Metrohm-DropSens). Each customised SPELEC equipment contains a halogen-deuterium lamp, a potentiostat and a suitable spectrophotometer. All of the components of the equipment are synchronised to ensure the correlation of electrochemical and spectroscopic techniques, ensuring reliable operando and time-resolved data acquisition. Both SPELEC devices were connected to each other to ensure the synchronisation of normal and parallel measurements. All measurements were performed using the DropView software (MetrohmDropSens).