N-Doping of Organic Semiconductor Materials

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NON-TECHNICAL DESCRIPTIONOrganic semiconductors are promising materials for flexible electronics such as solar cells, displays, and sensors. For many applications, their electrical conductivity must be increased by adding positive (p-type) or negative (n-type) charges. This process is known as molecular doping. While there are many p-type organic semiconductors, n-type organic semiconductors are far rarer. Moreover, they are less stable in ambient conditions, and it can be difficult to control their electrical conductivity. Advancing the field of organic electronics will require development of new electronic materials and processes for n-type doping. The goal of this project is to enhance the efficiency of n-type doping using a catalyst, a compound that enhances the speed of a chemical reaction. The investigator will combine synthetic strategies for new organic semiconductors with selection of n-type dopant-catalyst pairs to optimize the doping process. This research will result in a new class of n-type organic semiconductors with high-performance and enhanced stability. This research will also promote understanding on how the new n-type materials affect device performance. The PI’s educational goal is to foster a positive perception of organic electronic materials and devices. This will be accomplished through outreach to middle and high school students, coupling course instruction to undergraduate and graduate research projects, and providing internship opportunities at a start-up company to foster entrepreneurship.TECHNICAL DESCRIPTIONThe doping of inorganic materials has been instrumental in the progress of the semiconductor industry and advances in numerous fields including medical diagnostics, environmental science, and homeland security. For organic semiconductors, several strategies have yielded doped π-electron solids with greatly enhanced optical and electronic properties as well as novel materials, physical phenomena, and device concepts. However, these advances were largely enabled by p-doped (hole transporting) materials, while useful n-doped (electron-transporting) materials have been limited in chemical accessibility, doping efficiency, and environmental stability. This limits their use in devices where both p-type and n-type semiconductors are required. Recently, the PI and coworkers discovered that metal nanoparticles (e.g., Au) can catalytically assist/accelerate the doping of representative organic semiconductors by molecular dopants. This research project will: 1) Elucidate the mechanism of the catalytic n-doping process and expand the scope to other type of catalysts. 2) Explore other dopants and semiconductors, implementing to date unexplored structural design and synthetic strategies. 3) Characterize catalyzed vs uncatalyzed doped film properties in terms of composition, electronic structure, morphology, microstructure, and opto-electronic response. Thus, this study plans to bring n-doped organics to unprecedented levels in terms of molecular/macromolecular materials designs, their accessibility in scale, and their useful opto-electronic properties.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.