A Method to Control Morphology of BHJ OPVs Using End-functionalized Poly(3-hexylthiophene)(P3HT) Grafted to SQDs

Improving the power conversion efficiency of organic photovoltaic devices based on polymer-nanoparticle bulk heterojunctions remains a significant challenge that limits the commercial production of these technologies. There are a number of factors that contribute to the efficiency of photovoltaic devices including absorption, charge generation and charge separation, which ultimately rely on the morphology of the bulk heterojunction active layer. My work aims to improve these processes by developing a method to prepare end-group functionalized π[pi]- conjugated polymers that will be used to decorate the surface of nanoparticles thereby tailoring the interface between the polymer and the nanoparticle. This work involves the preparation of a novel pyridine terminated poly (3-hexylthiophene) with the propensity to coordinate cadmium selenide semiconductor quantum dots. The polymers were synthesized by a modified Grignard metathesis polymerization in the presence of different additives and reactions conditions that improve the yield of monofunctional products. The end-group composition of P3HTs prepared by in situ quenching of the GRIM polymerization method with tolyl-magnesium bromide was altered by adding reagents with an unsaturated double that coordinates with the active Ni0­[nickel zero] complex. The additives, 1-pentene and styrene, were shown to improve the monofunctional yield of tolyl-functionalized P3HTs, a model polymer, by interacting with the active Ni0 species and preventing oxidation addition at the initiating chain end. A method to tailor the donor/acceptor interface of bulk heterojunction organic photovoltaic devices by modifying the surface chemistry of semiconductor quantum dots (CdSe SQDs) will be presented. The ligands on CdSe SQD surfaces play an impactful role in their synthesis, solution properties and nanophase organization in a polymer matrix. In this work, I report a method to stabilize cadmium selenide (CdSe) SQDs in a poly(3-hexylthiophene) (P3HT) matrix through a series of successive ligand exchanges that results in P3HT chains decorating the SQD surface

Poly(3-hexylthiophene) Molecular Bottlebrushes via Ring-Opening Metathesis Polymerization: Macromolecular Architecture Enhanced Aggregation

We report a facile synthetic strategy based on a grafting through approach to prepare well-defined molecular bottlebrushes composed of regioregular poly­(3-hexylthiophene) (<i>rr</i>-P3HT) as the conjugated polymeric side chain. To this end, the <i>exo</i>-norbornenyl-functionalized P3HT macromonomer was synthesized by Kumada catalyst transfer polycondensation (KCTP) followed by postpolymerization modifications, and the resulting conjugated macromonomer was successfully polymerized by ring-opening metathesis polymerization (ROMP) in a controlled manner. The P3HT molecular bottlebrushes display an unprecedented strong physical aggregation upon drying during recovery, as verified by several analyses of the solution and solid states. This remarkably strong aggregation behavior is attributed to a significant enhancement in the number of π–π interactions between grafted P3HT side chains, brought about due to the bottlebrush architecture. This behavior is qualitatively supported by coarse-grained molecular dynamics simulations