Oxidative chemical vapor deposition (oCVD) results in heavily doped conductive polymer films using materials that are insoluble and infusible. oCVD of conjugated polymers can be used to create photoactive semiconductors in organic solar cells.
Vacuum fabrication of multilayered devices is not constrained by the requirement of finding orthogonal solvents to prevent mixing between layers during deposition. However, the high temperatures necessary to physically deposit polymers by vacuum thermal evaporation leads to polymer degradation, limiting materials to low-molecular weight organics. oCVD offers the benefits of vacuum processing, including parallel and sequential deposition, well-defined thickness control and uniformity, and inline integration with other standard vacuum processes (e.g. vacuum thermal evaporation). Additionally, oCVD is conformal over nonplanar substrates, enabling compatibility with substrates such as paper and textiles.
The present technology demonstrates the use of oCVD to process conjugated polymers (including insoluble polymers) via vacuum deposition. In this case, oCVD was used to obtain polythiophene (PT) by reacting thiophene monomer vapor with iron (III) chloride via oxidative polymerization to obtain a doped, conductive form of the polymer. Upon rinsing the film with methanol, the polythiophene was dedoped to obtain the semiconducting form. This polymer was deposited onto ITO-glass substrates (indium tin oxide) and successfully incorporated into efficient bilayer heterojunction photovoltaic devices with C60 (fullerene), resulting in power conversion efficiencies up to 0.8%.
- Combines the benefits of vacuum processing and semiconducting polymers
- Allows processing of polymer active layers without solubility, temperature, or substrate constrains