In this work, we report a major advance in the use of interfacial electrosynthesis at an ITIES to prepare free-standing, additive-free, reproducible, easily transferrable, scalable, and biocompatible PEDOT thin films in a single step at optimised ambient conditions. The external electrochemical driving force, the interfacial Galvani potential difference (∆ o w 𝜙), is applied using double potential step chronoamperometry (DPSCA). The IET reaction between an aqueous Ce 4+ oxidant and organic EDOT monomer, and subsequent oligomer deposition at the L|L interface, can be assisted or hindered by manipulation of ∆ o w 𝜙. We demonstrate an emergent enhanced biocompatibility of free-standing PEDOT thin films prepared at the ITIES, compared with films prepared by drop-casting commercial PEDOT:PSS surfactant-free ink, using normal human retina pigment epithelium (hTERT RPE-1) cells. The latter are a physiologically pertinent cell line given the application of PEDOT films in maculopathies. We functionally modified the PEDOT and PEDOT:PSS films through the incorporation of bioactive proteins and monitored the consequential effects on cell behaviour in each case. These findings foreshadow potential applications as suitable 2D conductive substrates for RPE and electrically active photoreceptor cells and the development of organic electrochemical cell transistors (OECTs) capable of electrochemically monitoring cell growth over >24 hr periods.