Self-assembled monolayers (SAMs) are molecules that bind to solids through adsorption. SAMs can be used as sensors for lethal bacterial enzymes, pH and conductivity indicators, and can inhibit corrosion. SAMs are incredibly useful due to the ability for chemical binding of molecules to the surface of a metal, like zinc oxide (ZnO), and can greatly change chemical and physical properties. ZnO specifically has a large variety of properties that are useful for surface modification. These properties include a wide band gap (3.37 eV), high exciton binding energy (~60 meV), and stable wurtzite structure. Through the process of SAMs, the surfaces of ZnO nanoparticles are modified with 16 phosphonohexadecanoic acid, 11 phosphonoundecanoic acid and 11 undecynylphosphonic acid. After binding an organic compound to a ZnO surface, a fluorescein, specifically 5 aminofluorescein, is attached to the organic molecule in order to serve as a fluorescent marker that can be used as a photosensor to facilitate charge transportation. By changing the properties of the ZnO surface layer, solar cell efficiency can be altered by increasing energy efficiency. The sample concentration and use of “linker” molecules will be altered in order to determine the optimum conditions for the modifications to the ZnO surface and the success of modification will be determined using infrared spectroscopy, dynamic light scattering, zeta potential, ultraviolet-visible spectroscopy, scanning electron microscopy, and electrochemistry. UV-Vis spectroscopy was used to determine the band gap of the surface modified nanoparticles. Band gap is the minimum energy required to excite an electron that is in its bound state into a free state in order to participate in conduction. By lowering the band gap, conductivity can occur more easily making ZnO ideal for solar cells. Initial testing has indicated that the band gap of our surface modified molecules is lower than that of the ZnO bulk material.

Modification of the surface of zinc oxide nanoparticles in order to increase efficiency of solar cells

253rd National Meeting (2017)

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