Graphene Oxide: Key to Efficient Charge Extraction and Suppression of Polaronic Transport in Hybrids with Poly (3-hexylthiophene) Nanoparticles

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Nanoparticles (NPs) of conjugated polymers in intimate contact with sheets of graphene oxide (GO) constitute a promising class of water-dispersible nanohybrid materials of increased interest for the design of sustainable and improved optoelectronic thin-film devices, revealing properties exclusively pre-established upon their liquid-phase synthesis. In this context, we report for the first time the preparation of a P3HTNPs–GO nanohybrid employing a miniemulsion synthesis approach, whereby GO sheets dispersed in the aqueous phase serve as a surfactant. We show that this process uniquely favors a quinoid-like conformation of the P3HT chains of the resulting NPs well located onto individual GO sheets. The accompanied change in the electronic behavior of these P3HTNPs, consistently confirmed by the photoluminescence and Raman response of the hybrid in the liquid and solid states, respectively, as well as by the properties of the surface potential of isolated individual P3HTNPs–GO nano-objects, facilitates unprecedented charge transfer interactions between the two constituents. While the electrochemical performance of nanohybrid films is featured by fast charge transfer processes, compared to those taking place in pure P3HTNPs films, the loss of electrochromic effects in P3HTNPs–GO films additionally indicates the unusual suppression of polaronic charge transport processes typically encountered in P3HT. Thus, the established interface interactions in the P3HTNPs–GO hybrid enable a direct and highly efficient charge extraction channel via GO sheets. These findings are of relevance for the sustainable design of novel high-performance optoelectronic device structures based on water-dispersible conjugated polymer nanoparticles.
This work was funded by Spanish MCIN/AEI/10.13039/501100011033 under projects PID2019-104272RB-C51, PID2019-104272RB-C52, PID2019-104272RB-C55, and PID2019-104739GB-I00. Financial support from Gobierno de Aragon (DGA) under project “Grupos Consolidados” T03_20R is acknowledged. E.C. is grateful for PhD grant BES2017-080020 funded by MCIN/AEI/10.13039/501100011033 and by “ESF Investing in your future”. M.N.R.’s work was financed by grant PID2019-104272RB-C52/PRE2020-094503 funded by MCIN/AEI/10.13039/501100011033 and by “‘ESF Investing in your future”’. R.A. acknowledges support from EU H2020 “ESTEEM3” (Grant number 823717) and Graphene Flagship (881603).