Poly(3-hexylthiophene) (P3HT) is one of the most popular conductive polymers for optoelectronic applications. [1] Their device operation critically depends on the nanocrystalline domain structure, i.e. the aggregate structure acquired by the polymer chains. Most common aggregates' distribution corresponds to H-aggregates, which implies charge transfer across the chains compared to those acquiring a J- aggregate structure with favorable charge transport along the chains. [2] We recently have shown that strong interactions between P3HT and water-dispersible graphene oxide can be obtained upon the formation of P3HT nanoparticles in aqueous dispersions. [3,4] These interactions enable a significant modification of the internal structure of P3HT aggregates towards a structure predominated by J-aggregates. Following this approach, in this work we have synthesized P3HT nanoparticles by the re-precipitation method in the presence of various types of water-soluble carbon nanostructures. Under scrutiny are graphene oxide flakes of different sizes, as well as nanocrystalline cellulose of type I and II. Of all the nanostructures exploited, the rarely investigated nanocyrstalline cellulose of type II, [5] exhibits significantly enhanced synergetic interface interactions with P3HT nanoparticles. This finding not only reveals a great potential towards improved thin film optoelectronic device structures, but even more underlines value of nanocellulose II for the development of green inks of photoactive polymers, ready to be used for printed electronics.

1 figure.-- Talk delivered at the HeteroNanoCarb-2019 Conference, Advances and applications in carbon related nanomaterials: From pure to doped structures including heteroatom layers, 2019, December 09th -- 13th, Centro de Ciencias de Benasque Pedro Pascual, in Benasque (Aragon, Spain).

Funding by EU (Project H2020-ITN 2014 642742), Spanish MINEICO (Project ENE2016-79282-C5-1-R1 (AEI/FEDER, UE), contract BES2017-080020 including FSE, UE, contract IJCI-2016-27789) and Government of Aragon (DGA-T03-17R and FEDER, UE).