Optical properties and charge-transfer process studies for efficient organic photovoltaic cells: ab-initio simulations

At the interfaces formed by two contacted materials (donor and acceptor) interesting phenomena with a big number of applications for designing optoelectronic devices take place. This is the operating principle of organic photovoltaic cells (OPCs) which have attracted much attention due to its low-cost of fabrication and clean conversion of light. The efficiency and viability of OPCs depend strongly on tailoring and control of the interfaces at the molecular scales. Despite this current understanding and for designing more efficient devices, the role played by the charge-separation processes and the optical properties at the interfaces need to be addressed carefully. Thus, this project will use ab-initio simulations based on many-body theory approximation (GW approximation) to model one of the most important processes taking place at the interfaces of OPCs, the charge-transfer process. This process is critical to device performance and depends sensitively on the electronic and atomic structure of the interfaces such as the energy alignment of the charge transferred states. In such a sense, the project will be devoted to suggest and study improved heterojunctions based on: graphene nanoribbons, organic semiconductors and dyes. Special attention will be given to nanoribbons as an acceptor due to its transparency and unique optoelectronic properties which allow tuning their band gap through a proper design of their length, width, and edge structure. Thus, we will tailor the nanoribbons by edge functionalization, doping and tuning of the band gap, in order to explore its role over the charge transfer states and obtain improved heterojunctions.