Dye-sensitized solar cells are a class of photovoltaics that have shown promise in producing electricity at a reasonable price. Although the processes limiting performance of the devices are quite well understood, their quantification has not been incorporated into a single consistent framework. In this study this framework, based on continuum charge transport equations, is presented and used to investigate the effectiveness of common characterisation methods. Approximate analytical solutions to the model are also derived and it is shown that these can be used to solve the device model inverse problem by fitting the solutions to impedance spectroscopy measurements. Experimental results indicate that the overall device model is a good description of the system and that it can be used to quantify different power loss mechanisms. Additionally some initial work was undertaken to formulate a charge transport model for a new class of photovoltaics called perovskite cells. The cell is modelled as a p-i-n heterojunction where the perovskite absorber is an intrinsic semiconductor sandwiched between two selective contacts. Simulations indicate that a significant built-in field drives free charges towards the contacts significantly improving charge collection.