Efficient Charge Transport in Assemblies of Surfactant‐Stabilized Semiconducting Nanoparticles

and optoelectronic devices. [ 10,11 ] Recently, there is a growing interest in using conjugated polymer nanoparticles to fabricate the active layer in polymer-based organic photovoltaic (OPV) devices. [ 12–14 ] One signifi cant advantage in using nanoparticles is that the individual electron-donor and electron-acceptor nanoparticles can be pre-formed with tunable size and internal aggregate structure and then self-assemble into well-defi ned active layer morphologies for OPV applications. [ 15,16 ] Moreover, the active layers can in principle be fabricated over large areas through ink-jet printing or spray-coating of stable nanoparticle dispersions. However, nanoparticle dispersions are typically stabilized by surfactants to prevent aggregation. Therefore, the general expectation has been that the surfactants might impede charge transport in conjugated polymer nanoparticle (CPN) assemblies, since the surfactants might increase the distance between the particles or create interfacial defects. To realize the full potential of using CPNs as active layers for OPV devices, it is imperative to demonstrate that CPN assemblies transport charges effi ciently. In this article we investigate impact of surfactants on the charge transport in CPN assemblies, and demonstrate that effi cient charge transport can be obtained in surfactant-stabilized semiconducting nanoparticle assemblies. Poly(3-hexylthiophene) was chosen as the conjugated polymer for our studies because it is well-studied in terms of charge mobility [ 17–19 ] and molecular packing, [ 20–22 ] allowing direct comparison of our measurements with the literature to understand better the impact of surfactants on charge transport. Polymer nanoparticles were synthesized by miniemulsion with different concentrations of sodium dodecyl sulfate (SDS). [ 23 ] Two commercially available poly(3-hexylthiophene) (P3HT) samples were used, 92% regioregular P1 with molecular weight 72 kDa and dispersity Ð = 2.5, and 97% regioregular P2 with molecular weight 30 kDa and Ð = 1.8. Charge carrier mobilities of spray-coated nanoparticle assemblies and