Theoretical Modelling of the Singlet Fission Process: from the gas phase to the effect of the environment

Conversion of sunlight into electricity prevails, until this day, as a promising source of renewable energy. Nevertheless, enhancement of conversion efficiencies in photovoltaic devices is desired. Different alternatives to bust this efficiency have been explored and applied. Among these alternatives, it has been proposed that the deposition of a layer of a material exhibiting singlet fission (SF) on top of a solar cell could increase its efficiency. This layer has two purposes: to absorb high energy incident photons that in current solar cells would be lost due to thermalisation, and to potentially generate two pairs of charge carries per single absorbed photon. Even though experimental attempts to demonstrate the potential of SF materials have been performed in recent years, two main drawbacks still limit their implementation: the small number of molecules known to exhibit SF and limited knowledge on how the process actually occurs. The aim of this thesis is, aided by computational techniques and theoretical methods, to offer insights in the SF process and attempt to provide answers to the drawbacks mentioned above. We focus on finding novel SF molecules and on providing a deeper understanding on how the process occurs.