Interface states and defect states commonly lead to some of the most interesting processes in next-generation solid-state optical devices such as organic and hybrid photovoltaics. We explore these states in a range of organic and hybrid materials by using transient optical absorption spectroscopy and field-dependent excited state spectroscopy. In all-organic systems, we find evidence for a connection between nanostructure and charge recombination mechanisms that appears to be linked to the susceptibility of different interfacial spin states to be influenced by an electric field. Our observations suggest new avenues for the potential of molecular design to control charge recombination and charge separation. We will also discuss our recent work focused on using transient optical spectroscopy to understand the role of photon energy and flux in determining excited state population kinetics in hybrid systems.