Tuning aggregation of poly(3-hexylthiophene) within nanoparticles

Nanoparticles derived from π-conjugated polymers have gained widespread attention as active layer materials in various organic electronics applications. The optoelectronic, charge transfer, and charge transport properties of π-conjugated polymers are intimately connected to the polymer aggregate structure. Herein we show that the internal aggregate structure of regioregular poly(3-hexylthiophene) (P3HT) within polymer nanoparticles can be tuned by solvent composition during nanoparticle fabrication through the miniemulsion process. Using absorption spectra and single-NP photoluminescence decay properties, we show that a solvent mixture consisting of a low boiling good solvent and a high boiling marginal solvent results in polymer aggregate structure with a higher degree of uniformity and structural order. We find that the impact of solvent on the nature of P3HT aggregation within nanoparticles is different from what has been reported in thin films.

Fabrication conditions for efficient organic photovoltaic cells from aqueous dispersions of nanoparticles

We report the processing conditions for fabricating efficient organic solar cells from aqueous dispersions of conjugated polymer nanoparticles.

Efficient charge transport in assemblies of surfactant-stabilized semiconducting nanoparticles

Charge transport through a semiconducting nanoparticle assembly is demonstrated. The hole mobility of low and high molecular weight and regioreglular poly(3-hexylthiophene) (P3HT) nanoparticles is on the order of 2 × 10(-4) to 5 × 10(-4) cm(2) V(-1) s(-1) , which is comparable to drop-cast thin films of pristine P3HT. Various methods are employed to understand the nature and importance of the nanoparticle packing.

Multiscale active layer morphologies for organic photovoltaics through self-assembly of nanospheres

We address here the need for a general strategy to control molecular assembly over multiple length scales. Efficient organic photovoltaics require an active layer comprised of a mesoscale interconnected networks of nanoscale aggregates of semiconductors. We demonstrate a method, using principles of molecular self-assembly and geometric packing, for controlled assembly of semiconductors at the nanoscale and mesoscale. Nanoparticles of poly(3-hexylthiophene) (P3HT) or [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) were fabricated with targeted sizes. Nanoparticles containing a blend of both P3HT and PCBM were also fabricated. The active layer morphology was tuned by the changing particle composition, particle radii, and the ratios of P3HT:PCBM particles. Photovoltaic devices were fabricated from these aqueous nanoparticle dispersions with comparable device performance to typical bulk-heterojunction devices. Our strategy opens a revolutionary pathway to study and tune the active layer morphology systematically while exercising control of the component assembly at multiple length scales.