Limonene as a Green Solvent for Depositing Thin Layers of Molecular Electronic Materials with Controlled Interdiffusion

Abstract

In the fabrication of thin-film electronic devices such as solar cells, molecular components are often deposited from solution by spin-coating. Toxic chlorinated solvents are widely used in this process, and environmentally benign alternatives are desirable. Ideally, these alternatives should be inexpensive, derived from renewable sources, and able to dissolve typical molecular electronic materials. Moreover, they should allow the creation of thin films in which the interdiffusion of different components can be controlled to optimize the performance of the resulting device. In an initial survey, we have examined the deposition of layers of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), which are benchmark molecular semiconductors that have been widely used together in solar cells as electron donor and acceptor, respectively. We have found that solutions in limonene (which is a green solvent produced by citrus fruits and other plants) are particularly effective for dep...