Grignard metathesis polymerization was used to synthesize a series of poly(3-hexylselenophene)-block-poly(3-hexylthiophene) copolymers with two different molecular weights and varying selenophene content. These polymers were characterized by optical absorption spectroscopy (film and solution), differential scanning calorimetry, powder X-ray diffraction, variable temperature absorption spectroscopy, and atomic force microscopy (on self-assembled polymer nanofibers). The selenophene to thiophene ratio has a large influence on optical properties, and absorption is tunable across the range of both homochromophores. We observe phase separation in the solid state in both pristine and annealed samples. When allowed to slowly assemble in solution, high molecular weight copolymers have a very sharp transition from the molecularly dissolved to the aggregated state. Most interestingly, increasing polyselenophene content induces the polymer to assemble more readily (at a higher temperature) but also appears to hinder the degree of ordered assembly when the thiophene block is not sufficiently long. This study furthers the understanding of the differences between these structurally similar conjugated polymer building blocks and provides insight into the factors that control heterocycle-induced phase separation.

Poly(3-heptylselenophene)-stat-poly(3-hexylthiophene) is synthesized and characterized in terms of its crystallinity and performance in an organic photovoltaic (OPV) cell. Despite the random distribution of units along the polymer main chain, the material is semi-crystalline, as demonstrated by differential scanning calorimetry and wide-angle X-ray diffraction. Thin-film absorption suggests an increased compatibility than seen with 3-hexylselenophene monomer. Optoelectronic properties are an average of the two homopolymers, and OPV performance is enhanced by a broadened absorption profile and a favorable morphology.

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A continuous-flow microreactor was used to synthetize II-VI semiconductor quantum dots (CdSe). In order to improve the size distribution of the nanoparticles, the synthesis was carried out in a two-step procedure. A seed solution was obtained in a separate nucleation step, followed by a controllable growth step. Quantum dots that are synthesized with the two-step method show a much narrower size distribution in comparison to those obtained in a conventional batch synthesis.