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 Ni^0­[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.