Optimizing the Optoelectronic Properties of Face-On Oriented Poly(3,4-Ethylenedioxythiophene) via Water-Assisted Oxidative Chemical Vapor Deposition

Engineering the texture and nanostructure to improve the electrical conductivity of semicrystalline conjugated polymers must address the rate-limiting step for charge carrier transport. In highly face-on orientation, the charge transport between chains within a crystallite becomes rate-limiting, which is highly sensitive to the π–π stacking distance and interchain charge transfer integral. Here, face-on oriented semicrystalline poly(3,4-ethylenedioxythiophene) (PEDOT) thin films are grown via water-assisted (W-A) oxidative chemical vapor deposition (oCVD). Combining W-A with the volatile oxidant, antimony pentachloride, yields an optimized electrical conductivity of 7520  ±  240 S cm^?1, a record for PEDOT thin films. Systematic control of π–π stacking distance from 3.50 Å down to 3.43 Å yields an electrical conductivity enhancement of ≈ 1140%. The highest electrical conductivity also corresponds to minimum in Urbach energy of 205 meV, indicating superior morphological order. The figure of merit for transparent conductors, σ_dc/σ_op, reaches a maximum value of 94, which is 1.9 × and 6.7 × higher than oCVD PEDOT grown without W-A and utilizing vanadium oxytrichloride and iron chloride oxidizing agents, respectively. The W-A oCVD is single-step all-dry process and provides conformal coverage, allowing direct growth on mechanical flexible, rough, and structured surfaces without the need for complex and costly transfer steps.