Effect of Crystallizable Solvent on Phase Separation and Charge Transport in Polymer-fullerene Films

The effect of 1, 3, 5-trichlorobenzene (TCB) as crystallizable solvent on poly[N-9'-heptadecanyl-2, 7-carbazole-alt-5, 5-(4', 7'-di-2-thienyl-2', 1', 3'-benzothiadiazole)] (PCDTBT) and [6, 6]-phenyl C₇₁ butyric acid methyl ester (PC₇₁BM) bulk heterojunction (BHJ) was investigated. We found that phase separation of PCDTBT and PC₇₁BM and formation of the condensed network of polymers were appropriately regulated by addition of TCB in the BHJ films, which were confirmed by optical microscopic, AFM, and TEM observations in addition to current-voltage analyses. Through the formation of a good continuous pathway for carrier transport by the addition of TCB, 2.5 times enhancement of the hole mobility in the BHJ film was attained from 5.82 × 10⁻⁵ cm² V⁻¹ s⁻¹ without TCB to 1.48× 10⁻⁴ cm² V⁻¹ s⁻¹ with 20 mg ml⁻¹ of TCB

Effect of Nanoparticle Concentration on the Convective Deposition of Binary Suspensions

We investigate the coupling between the suspension properties and the deposition process during convective deposition of aqueous binary suspensions of 1 μm silica microspheres and 100 nm polystyrene (PS) nanoparticles. The structures formed from this rapid and scalable process have use in a variety of optical, chemical, and biochemical sensing applications. At conditions that produce a well-ordered microsphere monolayer at a silica volume fraction of 20% in the absence of nanoparticles, we examine the effect of varying the concentration of nanoparticles from 0% to 16% on the quality of the microsphere deposition and the exposure of the microspheres within the PS layer. At low concentrations of nanoparticles, the deposition results in an instability that forms stripes parallel to the receding contact line. Optimum deposition occurs between 6% and 8% PS and forms a monolayer having the same high degree of uniformity as the monodisperse suspension is fabricated. For higher concentrations, the deposition is increasingly less uniform as a result of nanoparticle depletion destabilizing the microspheres. The degree to which each microsphere is buried by the nanoparticles in the deposited thin film increases with nanoparticle concentration. This variation in coverage also suggests interplay between deposition and nanoparticle engineered properties of the suspension that influence the deposited morphology