Nowadays, renewable energy sources are attracting a lot of attention due to the undesired environmental impact that fossil fuels are causing to the Earth. Solar energy is a sustainable alternative to the increasing world energy demand.

The main aim of this work was to design and synthetize novel molecules that could replace the polymers widely used as absorbers in organic solar cells and to replace spiro- OMeTAD used as a hole transporting material (HTM) in perovskite solar cells.

On the one hand, polymers are known for their good hole transporting properties, high solubility and good film forming abilities but they have a poor batch-to-batch reproducibility. Furthermore, spiro-OMeTAD is the best molecule to achieve reproducible and highly efficient perovskite solar cells. However, its complex and expensive synthesis and purification hinder its usage in industrial scale photovoltaics.

In order to overcome these problems, the rational design, synthesis and characterization of a variety of small molecules for both applications have been the focus of this thesis.