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

• Published in: Advanced functional materials 2021-04, Vol.31 (14), p.n/a
• Main Authors: Heydari Gharahcheshmeh, Meysam, Robinson, Maxwell T., Gleason, Edward F., Gleason, Karen K.
• Format: Article
• Language: English
• Subjects: Antimony; antimony pentachloride oxidant; Carrier transport; Charge transfer; Charge transport; Chemical vapor deposition; Conductors; Constraining; Crystallites; Current carriers; Electrical resistivity; Figure of merit; Iron chlorides; Materials science; Optoelectronics; Oxidation; oxidative chemical vapor deposition; Oxidizing agents; poly(3,4‐ethylenedioxythiophene); Stacking; Thin films; water‐assisted growth; π–π stacking distance
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.202008712

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, σdc/σop, 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. In poly(3,4‐ethylenedioxythiophene) (PEDOT) thin films with a highly face‐on orientation, the charge transport between chains within a crystallite becomes a rate‐limiting factor, which is highly sensitive to the π–π stacking distance. Engineering the π–π stacking distance in PEDOT films grown by water‐assisted oxidative chemical vapor deposition (oCVD) yields a record high electrical conductivity of 7520 ± 240 S cm−1.