Interfacial electrosynthesis at an ITIES bridges the fields of purely homogeneous (chemical) electron transfer reactions between redox couples, which are difficult to control, and finely controlled (electrochemical) heterogeneous electron transfer at conventional solid electrodeelectrolyte interfaces. This work demonstrates that interfacial electrosynthesis directly produces PEDOT thin films of any shape or size in a single step, with distinctive molecular architectures inaccessible in bulk solution or at solid electrode-electrolyte interfaces, and emergent properties that facilitate technological advances. Electrochemical control of thinfilm nucleation and growth at the L|L interface allows fine control over the morphology, transitioning from 2D films (flat on both sides with a thickness <50 nm) to "Janus" 3D films (with a flat and rough side, each showing distinct physical properties, and thickness >850 nm) by simply tuning the number of DPSCA cycles implemented. The PEDOT thin films were highly p-doped (approaching the theoretical limit), showed high π-π conjugation, and were processed directly as thin films without insulating PSS. As a result, these films were highly conductive without post-processing, with their ex situ conductivity determined as 554 (±77) S•cm -1 and a maximum in situ conductivity of ~5.35 S•cm -1 , more than 4 times greater than films prepared with the highest conductivity grade commercial PEDOT:PSS available from Sigma-Aldrich. Furthermore, when comparing the two conductive polymers, PEDOT thin films showed superior biocompatibility and suitability to be used as a scaffold for cellular growth without the need for further modification designed to promote cell adhesion or enhance viability. Bioactive molecules can be readily incorporated into PEDOT polymers as a further customisable parameter for cell growth studies. This opens an attractive avenue for potential new and improved OECT devices for monitoring cell behaviour over extended time periods, bio-scaffolds and medical devices, without the requirement for physiologically unstable and poorly biocompatible PSS.