Conjugated polymers have demonstrated promise in the fabrication of large-area, deformable electronic devices. Recently, donor-acceptor (D-A) copolymers, have gained increased attention due to their improved electronic performance compared to their homopolymer counterparts. Significant knowledge gaps exist in the process−structure−property relationships of D−A polymers, creating room for optimization. In order to improve device performance, the solution state of these polymers needs to be studied to establish clear relationships between solution-state structures, solid-state morphology, and charge transport properties. Previous work involved applying a materials informatics methodology to a curated dataset containing processing and performance information of published organic field effect transistors (OFETs), fabricated using the commercial D-A polymer, DPP-DTT. The methodology identified molecular weight (Mw) and solution concentration as influential parameters for OFET performance. While the influence of Mw on OFET performance has been investigated widely, the influence of the solution concentration still remains unclear. This talk investigates the influence of solution concentration on the OFET performance of conjugated polymers, with a focus on DPP-based D-A polymers. Preliminary experiments performed on high Mw (~ 300 kg/mol) DPP-DTT revealed that the critical overlap concentration (C*), identified from solution-state viscosity experiments, resulted in improved OFET hole mobility. It is hypothesized that the overlap of polymer aggregates at C* in the solution state contributes to improved charge transport in the solid film. More recent experiments revealed that this trend is generalizable across different Mw’s of DPP-DTT as well as other families of DPP-based polymers (PDPP-4T). Interestingly, a strong influence of solution concentration on hole mobility was also observed for homopolymers like P3HT, suggesting that solution-state concentration is a critical design parameter that impacts OFET performance across p-channel conjugated polymers.

Influence of solution concentration on the charge carrier mobility of DPP-based donor-acceptor polymers

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