Book Description

Dye-sensitized solar cells (DSCs) are among the promising photovoltaic technologies that could potentially replace the expensive silicon. Liquid electrolyte-based DSCs have the highest efficiency but they suffer from potential stability and encapsulation problems when manufactured at high volumes. Research groups are actively pursuing solid state dye-sensitized solar cells (ss-DSCs), which uses a solid-state hole-transport material to replace the liquid electrolyte. SS-DSCs can potentially achieve higher power conversion efficiencies than the liquid-electrolyte because the open-circuit voltage can be adjusted by the choice of different hole-transport materials. However, current ss-DSCs are limited by both pore filling and electron-hole recombination such that the optimal thickness is around 2 microns, far thinner than the thickness needed to achieve good optical absorption. This thesis presents results that address two challenges facing the field of ss-DSC research - what is limiting the thickness of the device, and what can we do to boost light absorption and power conversion efficiency? In the first part, we describe how pore filling of hole-transport materials inside mesoporous TiO2 films is a limiting factor to the device thickness. This is accomplished by three closely-related pore filling projects: (a) quantifying the pore filling of hole-transport materials inside mesoporous TiO2 films; (b) experimenting with new methods to improve pore filling fraction; and (c) investigating the effect of pore filling on photovoltaic performances of ss-DSCs and the underlying photophysical mechanisms. This brings new physical understanding of the importance of pore filling and how pore filling a effects the photovoltaic performances. In the second part, we describe a new device architecture to increase the absorption through the use of plasmonic back reectors, which consist of two-dimensional (2D) array of silver nanodomes. They are incorporated into the ss-DSCs by nanoimprint lithography, and they enhance absorption through excitation of plasmonic modes and increased light scattering.