Charge Transfer and Photovoltaics with Inorganic Semiconductor Nanoparticles

Colloidal semiconductor nanoparticles (NP) are emerging as a new class of solution-processable materials for low-cost, flexible, thin-film photovoltaic devices. The NP quantum size effect allows researchers to selectively tune the NP 19s absorption coverage across a broad range of the solar spectrum. Recent advances have led to a power conversion efficiency of 7% for NP-based solar cells. However, exciton generation, separation, and recombination processes in these devices are not well-understood, which largely limit further improvement of the efficiency. Thus, this dissertation studies the underlying processes that control the kinetics for photogenerated charges in the NP-based devices. The first work in this dissertation addresses how the size-tunable energetics of the NPs change once they are electronically coupled with a conductive substrate. The second study focuses on the energy architecture and alignment for the NP with respect to the energy levels of electron and hole transporting media. The third study explores the donor-acceptor interfacial charge transfer between a conjugated copolymer and a NP with the goal of driving efficient charge separation for inorganic/organic hybrid solar cells. The last study investigates the effect of thermal annealing on the photovoltaic performance for PbS NP/TiO2 depleted heterojunction solar cells. The findings in these studies provide a deeper understanding of charge transfer kinetics for the NP, and may facilitate the development of the NP-based photovoltaics for use in next generation solar cells