2024 AIChE Annual Meeting

(461e) Chemical Vapor Deposition of Conjugated Polymers for Flexible Lightweight Photovoltaics

Author

Gleason, K. K. - Presenter, Massachusetts Institute of Technology
Conjugated polymers exhibit promising mechanical properties crucial for the advancement of flexible energy and electronic devices. However, their widespread application necessitates precise molecular engineering to enhance electrical conductivity and carrier mobility. Indeed, the nanostructure and properties of conjugated polymers can be precisely controlled by chemical vapor deposition (CVD). The CVD conditions for semicrystalline poly(3,4-ethylene dioxythiophene) (PEDOT) have been tailored to achieve a face-on crystallite orientation rather than the more common edge-on orientation. The face-on orientation reduces the barrier to charge carrier transport between crystallites, thereby dramatically improving in-plane electrical conductivity. Additionally, the CVD method provides precise and systematic control over the b-axis lattice parameter (π-π stacking distance) within the crystallites. Decreasing the b-axis lattice parameter increases the charge transfer integral and enhances charge carrier mobility within the crystallites. Reducing the π–π stacking distance from 3.50 Å to 3.43 Å, yielding a dramatic electrical conductivity enhancement of ≈1140%. Improved electrical conductivity also correlates with superior morphological order, as indicated by reduced Urbach energies. A maximum electrical conductivity of 7520 ± 240 S cm−1 was achieved for CVD PEDOT. This conductivity exceeds that of the brittle inorganic transparent conductor indium tin oxide (ITO). Furthermore, the single-step, all-dry CVD growth process offers seamless integration onto various substrates, including thermally sensitive plastics, eliminating the need for complex transfer steps. This compatibility with flexible and wearable device substrates positions CVD PEDOT as a key enabler for diverse applications. CVD PEDOT has been successfully integrated into a variety of flexible devices, including photovoltaics. Such flexible and lightweight solar cells are desired for applications such as self-powered aviation, wearable electronics, and the Internet of Things (IoT). Integration of CVD PEDOT as a hole transport layer in inverted perovskite solar cells not only improved power conversion efficiency but also enhanced shelf-life stability. CVD PEDOT was combined with CVD-grown graphene, parylene, and PbS quantum dots to achieve flexible photovoltaics with a power conversion efficiency of 7.1% and a power-per-weight of 12.3 W g−1. These findings underscore the immense potential of CVD PEDOT in shaping the future of flexible and lightweight energy solutions.