This thesis presents a collection of work investigating the optical properties of lead halide perovskites for optoelectronic applications. Lead halide perovskites are currently the state-of-the-art in terms of efficiency for thin-film photovoltaics, yet they are not fully understood and require further studies to elucidate their fundamental properties. Firstly in this thesis, the optical constants for lead halide perovskite thin films are determined using spectroscopic ellipsometry, providing important information for future optical modelling and calculations of the electronic structure. Following this, physical insights into the charge carrier dynamics in these materials are provided, revealing the effects of material disorder over a large range of temperatures. In relation to the charge carrier dynamics, the crucial topic of grain boundaries in lead halide perovskites is also investigated, showing their detrimental effects by providing non-radiative recombination centres in perovskite materials. Lastly, an application of colloidal semiconductor nanocrystals for perovskite solar cells is investigated, with the aim to enhance photocurrent in the devices. The prospect of this is shown by the successful dispersion of colloidal CdTe core-type quantum dots in the hole-transporting layer within solution-processed photovoltaic devices. This work is a promising advancement towards perovskite solar cells employing additional light harvesting processes from nanomaterials.