title: Multiscale active layer morphologies for organic photovoltaics through self-assembly of nanospheres.
abstract: 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.
authors.affiliation: Department of Chemistry, University of Massachusetts Amherst , Amherst, Massachusetts 01003, United States.
authors.forename: Timothy S
authors.initials: TS
authors.lastname: Gehan
authors.forename: Monojit
authors.initials: M
authors.lastname: Bag
authors.forename: Lawrence A
authors.initials: LA
authors.lastname: Renna
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Shen
authors.forename: Dana D
authors.initials: DD
authors.lastname: Algaier
authors.forename: Paul M
authors.initials: PM
authors.lastname: Lahti
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Russell
authors.forename: Dhandapani
authors.initials: D
authors.lastname: Venkataraman
keywords: Aqueous Dispersions; Hierarchical Assembly; Morphology; Organic Photovoltaics; Polymer Nanoparticles; Random Assembly