Organic solar cells: Synthesis and testing of novel, soluble fullerene derivatives

While less efficient than their inorganic counterparts, solution-processed organic solar cells have potential for inexpensive production. Fullerenes have proven useful in organic solar cells because of their solid-state order and high electron mobility. However, their near insolubility in organic solvents makes solution-processing difficult. It has been shown that fullerenes and soluble acenes can be covalently bound by utilizing the Diels-Alder pathway. In doing so, the LUMO energy level of the fullerene is altered. Our goal was to create novel fullerene derivatives that would π-stack in the solid state, be soluble, and have a LUMO energy level suitable for use as an acceptor material in a solar cell. After purification, the derivatives were paired with a donor material in a bulk heterojunction solar cell and the performance tested. Our results yielded a new crystalline fullerene derivative which demonstrated photovoltaic behavior and may potentially be used in high-efficiency organic solar cells.